张硕
, 简星, 张巍
厦门大学近海海洋环境科学国家重点实验室,海洋与地球学院,福建 厦门 361102
Zhang Shuo, Jian Xing, Zhang Wei
中图分类号: P597.3
通讯作者:
*通信作者:简星(1987-),男,江西上高人,副教授,主要从事沉积地质学及沉积地球化学研究.E-mail:
收稿日期: 2018-06-15
修回日期: 2018-10-12
网络出版日期: 2018-11-20
版权声明: 2018 地球科学进展 编辑部
基金资助:
作者简介:
First author:Zhang Shuo(1995-), male, Hanzhong City, Shaanxi Province, Master student. Research areas include sedimentary geology and sedimentary geochemistry. E-mail: zhangshuomarine@163.com
作者简介:张硕(1995-),男,陕西汉中人,硕士研究生,主要从事沉积地质学及沉积地球化学研究.E-mail:zhangshuomarine@163.com
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摘要
基于单颗粒碎屑磷灰石原位分析的物源分析是沉积地质学研究的一种重要手段。磷灰石中Sr,Y和稀土等微量元素含量由SiO2含量和所在熔体中的分配系数控制,微量元素的含量在不同岩石的磷灰石中差异较大,可作为指示其母岩类型的重要指标。磷灰石在物源分析中的应用可归纳为以下3个方面:①元素地球化学,特征元素包括Sr、Y、稀土元素(REE)等;②同位素地球化学,包括Sr-Nd同位素、Lu-Hf同位素等;③单颗粒多法定年,即同颗粒磷灰石进行(U-Th)/He、裂变径迹和U-Pb定年分析。综合上述3个方面可获得磷灰石的母岩类型、形成条件和后期演化、源区抬升剥蚀史、沉积区沉降史等信息。尽管碎屑磷灰石的热年代学目前在沉积物源研究中运用广泛,但基于碎屑磷灰石元素及同位素地球化学(包括磷灰石U-Pb同位素定年)的沉积物源判别仍处于起步阶段,在沉积地质学、盆地分析、构造地质学等研究领域具有广阔的应用前景。
关键词：
Abstract
In situ analysis of detrital apatite is a significant approach to sedimentary provenance analysis, which is an important aspect in sedimentary geology study. Several trace elements such as Sr, Y and Rare Earth Elements (REEs) concentrate in apatites, and the distribution of these elements depends on the content of SiO2 and the distribution coefficient of the melt, thus the trace element abundances is obviously different in different rocks. These features can be used to indicate parent-rocks of detrital apatites in sedimentary rocks. The approaches and proxies of detrital apatite to sedimentary provenance analysis can be summarized as follows. ①elemental geochemistry, such as Sr, Y, REEs, the approaches including chondrite-normalised REE distribution patterns of apatites, Classification and Regression Tree (CART) and discriminant plots of REE parameters; ②isotopic geochemistry, including Sr-Nd and Lu-Hf isotopes; ③Multi-dating, including low-temperature thermochronology such as (U-Th)/He (AHe)and Fission Track (AFT) dating, and high-temperature thermochronology such as U-Pb dating. Based on an integrated analysis using these methods, we can get various and comprehensive geological information such as the rock type, formation conditions and evolution of source rocks, the history of uplift and exhumation of source areas and even the subsidence history of sedimentary basins. Although the low-temperature thermochronology of detrital apatite is widely used in sedimentary provenance analysis, the elemental and isotopic geochemistry, as well as the U-Pb dating, remains to be developed. These approaches are supposed to have wide application prospects in several research areas such as tectonics, sedimentary geology basin analysis and even paleoclimatology.
Keywords：
沉积物源分析的内容主要包括源区母岩类型及岩石组合判别、构造背景重建、古地理及古气候恢复以及沉积区沉积体系再现等方面[1]。传统的分析方法包括重矿物方法、黏土矿物学方法、岩石学方法和全岩元素地球化学方法等[2],但是这些常规的分析方法得到的往往是物源供给平均效应的结果,并不适用于沉积源区多元化的沉积条件[3]。随着技术条件的不断提高,特别是激光剥蚀等离子质谱技术(LA-ICP-MS)在固体地学领域的广泛运用,碎屑单矿物的元素地球化学、同位素、热年代学的研究为克服上述方法的缺陷提供了可能,同时也使得沉积学研究朝着定量的方向发展,已成为沉积学研究的热点。碎屑锆石因其高稳定性在沉积物源研究中运用最为广泛[4],碎屑磷灰石的热年代学也是沉积物源分析研究中常见的手段[5],但对其元素、同位素地球化学示踪方法的关注不多。
磷灰石作为碎屑沉积岩中常见的重矿物,可来源于三大类岩石,在花岗岩、花岗伟晶岩、榴辉岩、磷块岩等岩石中较为常见。磷灰石(Ca5[PO4]3(OH,F,Cl))富集Sr,Y和稀土元素(Rare Earth Element, REE)等不相容元素,而且微量元素的含量受SiO2含量和所在熔体中的分配系数所控制,因此微量元素的含量在不同岩石的磷灰石中差异较大,可作为指示其母岩类型的重要指标[6]。此外,磷灰石的热年代学——(U-Th)/He定年体系(AHe)和裂变径迹定年体系(Apatite Fission Track, AFT)能够反映磷灰石冷却的低温热历史信息[7],磷灰石的U-Pb年龄可以反映晶体的高温热历史信息[8],将二者结合能够提供磷灰石更完整的热历史信息[9]。值得注意的是,与锆石相比,磷灰石具有相对弱稳定性,即在酸性地表水条件下较易风化[10],可作为初次沉积旋回的代表矿物,能够直接反映源区信息[11]。近年来已有利用碎屑磷灰石的地球化学和热年代学进行物源分析的报道,如Malusà等[12]对意大利波河物源分析的研究中,系统地对碎屑磷灰石进行了元素地球化学、Sm-Nd同位素和热年代学研究。但稳定克拉通背景下的沉积物可能会经历多次沉积旋回,不稳定组分易丢失,使用碎屑磷灰石进行沉积物源示踪可能产生错误的结果。本文主要介绍来自不同类型岩石的磷灰石地球化学特征,结合国内外的最新研究进展,对碎屑磷灰石在物源分析中的应用进行总结。
磷灰石属磷酸盐矿物,是重要的含磷矿物,六方晶系,链状结构;空间群
磷灰石化学式为Ca5[PO4]3(OH,F,Cl),Ca2+可被Ce3+,Sr2+,Na+,Y,Mn,Th和REE等类质同象替换[6,17],[PO4
磷灰石微量元素组成常用LA-ICP-MS测定。岩浆岩中的磷灰石大部分元素没有成分分带,但是Th和U等元素存在分带,在外围存在一个约20 μm厚的包壳,其U和Th含量与磷灰石中U和Th整体含量存在明显差异[20,21,22,23],因而会影响U-Pb定年和(U-Th)/He定年。为避免U和Pb成分分带带来的误差,Spiegel等[24]提出将磷灰石最外围的20 μm磨蚀掉之后再进行测试。高压—超高压变质带中的磷灰石存在明显的成分分带,以REE为例,新疆西南天山榴辉岩中的磷灰石除Lu之外,其余REE的含量从边部到核部升高数倍至2个数量级[25],大别—苏鲁榴辉岩的磷灰石中从边部到核部轻稀土元素(Light Rare Earth Element, LREE)含量上升3~5倍,重稀土元素(Heavy Rare Earth Element, HREE)含量下降2~4倍[26]。因此在进行LA-ICP-MS分析时必须要考虑成分分带带来的影响,在对碎屑磷灰石进行测试时,尽可能选取相同或相似位置的测试点位。
磷灰石富集S和Y等不相容元素,且微量元素含量的变化与全岩SiO2含量有关,表明母岩的分异程度为磷灰石化学组成的主要控制因素,例如分异过程中Y,Mn和HREE在逐渐富集,而Sr含量逐渐降低[27],因此通过元素含量特征或二元图解来判断母岩类型是完全可行的。磷灰石U和Th含量较低,而且Th含量在高分异度岩石的磷灰石中含量更低,原因是独居石在结晶过程中会吸收Th和LREE。U与之相反,在花岗岩和花岗伟晶岩中含量为20×10-6~25×10-6,在辉绿岩中为2.3×10-6~4.2×1
REE在磷灰石中较为富集,∑REE含量取决于母岩中的REE组成,其中碳酸岩中的磷灰石REE含量最高,可达数个百分点[28],最小值出现于花岗伟晶岩和辉绿岩[6]。磷灰石REE球粒陨石标准化配分模式则取决于母岩性质特别是分异程度[15,29]。
磷灰石中常见流体包裹体以及锆石、独居石、榍石等矿物包裹体,挑选样品时尽量避免选取有包裹体的磷灰石,在进行测试时,测试点位必须避开包裹体。
磷灰石广泛存在于三大岩类中,下面从3个方面论述各类型岩石中的磷灰石矿物学和矿物化学特征。
Hoche等[30] 认为岩浆岩中磷灰石的晶习和形态与其形成条件有关,等径粒状磷灰石多形成于近平衡条件,岩浆结晶晚期磷灰石可形成于矿物之间,自形程度较差;针状磷灰石形成于快速冷凝或远离平衡条件的环境。磷灰石在碱性岩中紧密堆积,常与霞石和长石共生。磷灰石在基性岩中与磁铁矿或钛铁矿共生,有时出现于斑晶中。花岗岩中的磷灰石多为细针状出现于造岩矿物间隙中[31]。铁矿床中的磷灰石晶体颗粒较大,如内蒙古黑鹰山铁矿中磷灰石粒径从数毫米到数厘米,最大者为14 cm×2 cm[32];江苏宁芜陶村铁矿中磷灰石粒径为0.5~2 mm,少量达5 mm[33];河南舞阳赵案庄铁矿中磷灰石粒径为0.3~1.5 mm[34]。
矿物化学上,大部分岩浆岩中的磷灰石为氟磷灰石,橄榄岩捕掳体中可见桃红色的羟基磷灰石[6]。微量元素能够通过类质同象替换进入到磷灰石中,因此不同岩浆岩中磷灰石的微量元素差异明显,可作为判别磷灰石来源的重要依据[29]。
磷灰石中∑REE含量取决于母岩中的REE组成,其中碳酸岩中的磷灰石REE含量最高,可达数个百分点,最小值出现于花岗伟晶岩和辉绿岩[6,28]。此外,各岩石中磷灰石的REE球粒陨石标准化配分模式也有较大差别(图1),球粒陨石数据来自参考文献[44]。
图1 各类型岩石中磷灰石REE球粒陨石标准化配分模式图
(a)~(c) 数据来自参考文献[
Fig.1 Chondrite-normalised REE distribution patterns of apatites from different rock types
The data in (a)~(c) comes from reference[19]; The data in (d),(e) comes from reference[6]; The data in (f) comes from references[35,36];The data in (g) comes from references[32~34]; The data in (h) comes from references[37,38]; The data in (i) comes from reference[39];The data in (j) comes from reference[40]; The data in (k) comes from reference[41]; The data in (l) comes from references[42,43]
磷灰石是高压—超高压变质带中常见的矿物,在退变质过程中仍能够稳定存在。目前对变质岩磷灰石的研究主要集中于榴辉岩。
榴辉岩中的磷灰石最显著的辨别特征是晶体中的出溶结构。近年来所报道的磷灰石出溶结构包括磁铁矿、黄铁矿、磁黄铁矿、独居石、锶重晶石等,其宽度在1~10 μm,长度几微米到几十微米,多呈柱状或棒状,长宽比大于10∶ 1[45,46,47]。
榴辉岩中磷灰石以高Cu和Ti为特征。REE特别是LREE含量很高,∑REE的范围很大,南天山超高压变质带中为12×10-6~657×10-6,苏鲁榴辉岩中为296×10-6~6 965×10-6[24,41],REE球粒陨石标准化配分模式图解如图1k所示。榴辉岩中磷灰石的REE配分模式与母岩的退变质程度有关,退变质程度越高,∑REE特别是LREE含量越低。
磷灰石在沉积岩中主要产出于碎屑沉积岩和磷块岩,但由于弱稳定性,碎屑沉积岩中的磷灰石无法再经历剥蚀搬运作用进入沉积物中,因此本文只讨论磷块岩中的磷灰石特征。
磷块岩中的磷灰石粒径为0.01~1 mm,多呈柱状或粒状,可见半月形、S形、弯钩形等弯曲变形形态,常与石英伴生[48]。其REE球粒陨石标准化配分模式如图1l所示,沉积磷块岩中的磷灰石REE配分模式图较为平直,REE分馏不明显,Eu具有中等负异常,部分磷灰石具有弱—中等Ce负异常。
沉积岩中碎屑磷灰石的微量元素地球化学、多法定年、Sr-Nd同位素、Lu-Hf同位素等方法可以广泛地运用于沉积物源分析研究中,下面对这些方法进行简要介绍。
前文已述及磷灰石中微量元素含量范围很大,且不同来源的磷灰石微量元素差异较大,因此可根据微量元素含量及元素之间的比值对磷灰石母岩进行判别。Belousova等[6]利用分类回归树(Classification and Regression Tree, CART)对磷灰石母岩进行判别。本文依据前人部分数据对其中一张CART进行改进(图2)。图2以微量元素含量或比值作为依据,对磷灰石母岩进行逐步分类,直至确定其母岩类型,该图有2个优点:①准确度高,准确率除花岗伟晶岩为79%之外,其余岩石类型均在95%以上;②所用元素种类少,易于建立较大数据库进行对比。
图2 辨别磷灰石母岩类型的分类回归树
虚线部分为本文改动或增加部分,增加部分数据来源:榴辉岩数据来自参考文献[25,41];碳酸岩数据来自参考文献[40,49];花岗岩数据来自参考文献[19,50];铁矿床数据来自参考文献[33,37]
Fig.2 CART for the recognition of apatites from different rock types
The dotted lines mean the modified or added, the data in added part: The data in eclogite comes from references[25,41]; The data in carbonatite comes from references[40,49]; The data in granite comes from references[19,50]; The data in iron deposit comes from references[33,37]
由于稀土元素对成岩环境的反应极为敏感,来源不同的磷灰石稀土配分模式差异较为明显,详见图1,因此可以用稀土配分模式来反映母岩类型。
Belousova等[6]根据磷灰石的稀土特征参数及微量元素含量,分别绘制了Sr-Y图解、 Y-Eu/Eu*图解、Mn-Sr图解、(Ce/Yb)N-/∑REE图解,上述图解的组合使用能够对大部分的磷灰石母岩类型进行有效判别,但是该图解存在一定缺陷:①该图解中只包含了部分岩浆岩,并未涉及到沉积岩及变质岩;②部分岩石如花岗岩和花岗伟晶岩在4个图解中均具有较大的重合区域因而无法对其进行辨别。
本文参照上述图解,分别作出(Gd/Yb)N-δEu图解、(La/Sm)N-(La/Yb)N图解、(La/Yb)N-∑REE图解(图3)。
图3 不同岩石类型的二元判别图解(a)(Gd/Yb)N-δEu图解;(b)(La/Sm)N -(La/Yb)N图解;(c)(La/Yb)N-∑REE图解;碳酸岩数据来自参考文献[40,49];二辉橄榄岩、辉绿岩数据来自参考文献[
Fig.3 Fields of apatite composition from different rock types, proposed as discriminant plots (a) Plot of (Gd/Yb)N-δEu, (b) Plot of (La/Sm)N -(La/Yb)N, (c) Plot of (La/Yb)N-∑REE. The data in carbonatite comes from references [40,49]; The data in lherzolite and dolerite comes from reference[6]; The data in syenite comes from references[35,36]; The data in carbonatite comes from references[19,50~52]; The data in granitic pegmatite comes from reference[39]; The data in magmatic iron deposit comes from references[37,38]; The data in hydrothermal iron deposit comes from references[32~34]; The data in eclogite comes from reference[41];The data in amphibolite comes from reference[53]; The data in phosphorite comes from references[42,43]
通过上述图解可对绝大部分的磷灰石母岩类型进行判别,但个别类型岩石来源的磷灰石无法完全辨别,如正长岩和橄榄岩在3个二元图解中均具有较大面积的重合,辉绿岩区域在3个图解中完全被岩浆型铁矿覆盖,其原因可能有2种:①部分类型岩石来源的磷灰石数据量较小;②母岩中磷灰石的形成、演化的条件差异较小。因此,如果在物源判别中磷灰石落到上述重合区域内,应当再使用其他方法对母岩进行辨别。
目前已有利用磷灰石的元素地球化学特征判别沉积物来源的报道,Morton等[54]对南里海盆地古库纳河和古伏尔加河的物源分析中,利用LA-ICP-MS测定碎屑磷灰石中的元素含量,发现古伏尔加河沉积层的碎屑磷灰石母岩类型中花岗岩类占到了42%~63%,辉绿岩占到了19%~20%;古库纳河沉积层中高分异度岩石较少,花岗岩类贡献率为10%~32%,辉绿岩占11%~19%,铁矿石占19%~20%,个别组中二辉橄榄岩占26%;Malusà等[12]测定了意大利波河流域中碎屑磷灰石的微量元素含量,发现与External地块相比,来源于阿尔卑斯山中部Lepontine穹隆的碎屑磷灰石HREE富集而Ce和U丰度值较低。
多法定年是指对同一单矿物颗粒进行多种手段定年获取不同的年代学年龄,从而获得源区和沉积区的热历史[55],目前磷灰石多法定年常用的手段为三法定年和单颗粒双法定年。若将磷灰石多法定年和其他定年方法结合,源区结晶—抬升冷却信息和沉积区的沉降—抬升历史信息将更加完整(图4a)。Carrapa等[55]在对Andean Puna中央高原始新世沉积物的研究中首次使用了磷灰石三法定年。本文将分别对磷灰石的低温热年代学、U-Pb定年和多法定年在物源分析中的应用进行介绍。
图4 磷灰石多法定年示意图
(a)岩石抬升、剥蚀过程中的热历史轨迹;(b)多法定年峰值图;数据来自参考文献[55,56]
Fig.4 Illustration of Multi-dating of detrital apatite
(a)The track of thermal history during lifting and exhumation;(b)The density diagrams of multi-dating; The data comes from references[55,56]
5.2.1 磷灰石低温热年代学
磷灰石是低温热年代学研究中应用最广泛的矿物之一[57],能够记录岩石在抬升过程最后阶段的低温热历史,对其他同位素定年系统形成补充,提供更加完整的热历史数据。目前磷灰石热年代学最常用的手段是(U/Th)-He定年和裂变径迹定年。
AHe体系封闭温度是已知定年体系中最低的,仅为70 ℃左右[58,59],因此可反映地质作用冷却过程最后阶段的信息[60,61]。但是AHe定年过程复杂、周期长、成本高、精度低等局限性进一步制约了该方法的发展[62]。付山岭等[63]报道了原位(U-Th)/He同位素定年技术,为解决上述问题提供了可靠选择,或成为未来AHe定年的新方向。AFT的封闭温度为120 ℃左右,可用于重塑地壳上部3~5 km内数百万年以来的热历史[64]。
近年来,已有学者将磷灰石的热年代学应用于物源分析当中。如Stock等[65]利用AHe概率密度函数(Probability Density Function, PDFs)对美国加利福尼亚州内华达山脉Inyo Creek和Lone Pine Creek水系沉积物进行来源判别,Inyo Creek水系沉积物AHe的PDFs预测峰值(31 Ma)与测定峰值(33 Ma)相似,表明源区侵蚀速率一致和砾石随水流的快速搬运与堆积,Lone Pine Creek水系沉积物AHe的PDFs预测峰值(62 Ma)与测定峰值(41 Ma)相差较大,表明沉积物多源于低海拔流域,缺乏年龄较老的沉积物是由于高海拔地区沉积物堆积于冰斗和快速抬升过程中的快速剥蚀;常健等[66]在塔里木盆地北缘与南天山构造—沉积耦合关系的研究中,测得塔北隆起地层和南天山AFT年龄分别为10~24 Ma和11~16 Ma,AFT良好的对应关系表明塔北隆起地层中的磷灰石来自南天山和库车坳陷北缘。
5.2.2 磷灰石U-Pb定年
磷灰石U-Pb体系封闭温度为450~550 ℃[11,67],记录了磷灰石通过该温度段的时间,除了能获得磷灰石的高温热历史之外,还可以根据冷却速率推断其结晶时间,如Danišík等[9]测得德国Schwarzwald矿床磷灰石U-Pb年龄为(289.5±4.5)Ma,根据半径为0.5 mm左右的磷灰石冷却时间为10 ℃/Ma[68],推算其结晶年龄为(289.5±4.5)~(314±6) Ma。磷灰石U-Pb年龄可与低温热年代学信息相结合,成为物源分析的重要手段。
随着技术的不断提高,关于磷灰石的原位U-Pb测年方法近年来也有报道。周红英等[69]结合前人研究,利用LA-MC-ICP-MS建立了磷灰石微区原位U-Pb同位素定年新方法,该方法克服了传统磷灰石U-Pb定年中普通铅含量高、放射性成因铅含量低、分析流程复杂等缺陷,从而获得了较为精确的磷灰石U-Pb年龄。
5.2.3 磷灰石多法定年
相比于锆石,磷灰石具有弱稳定性,即在酸性地表水条件下较易风化,因此可作为初次沉积旋回的代表矿物,直接反映源区信息,对于解释多旋回或多源区沉积来源具有一定优势。Carrapa等[55]和Decelles等[56]对Andean Puna中央高原始新世沉积物来源和盆地沉降史的研究中,将碎屑磷灰石三法定年(即U-Pb、AFT和AHe)、碎屑锆石U-Pb定年和碎屑白云母Ar-Ar定年结合,确定其源岩形成于前寒武—早显生宙时期,在志留纪—早石炭世发生抬升冷却,自早—中白垩世以来抬升速度加快并于始新世开始发生剥蚀,结果如图4b所示。Olivetti等[70]利用AFT和磷灰石U-Pb双法定年,对南极洲Victoria盆地沉积物进行物源判别,结果显示AFT年龄小于40 Ma,磷灰石U-Pb年龄的2个峰值为530和610 Ma,与Victoria南部600 km之外的Beardmore和Scott冰盖相对应;Zattin等[71]对南极洲西罗斯海沉积物物源判别的研究中,利用磷灰石U-Pb年龄和AFT年龄将源区物质分为快速冷却和缓慢冷却2类,快速冷却的火成磷灰石表明始新世—渐新世在Mount Morning大火成岩省前部存在一个未知的火山。缓慢冷却的磷灰石的AFT年龄比临近的中央山脉年轻,表明沉积物大部分来自Discovery Accommodation带,仅少部分来自Royal Society山脊,而AFT和AHe之间的差值表明始新世中央山脉的中等—快速的冷却事件。
磷灰石的Sr和Nd含量较高而Rb含量较低,因此Sr-Nd同位素可以提供相应的地球化学信息,但是磷灰石中的Sr会有显著的成分分带现象[72,73]。侯可军等[74]利用LA-MC-ICP-MS技术,建立了磷灰石原位Sr-Nd同位素分析方法,可以避免成分分带带来的影响,提供更加精确的地球化学信息。
磷灰石Lu-Hf同位素常用LA-MC-ICP-MS方法测定,与传统的热电离质谱法相比,具有适用范围广、精确度高、流程简单、周期短的优点[75]。Cherniak[76]认为磷灰石中REE的封闭温度大于等于700 ℃,Barfod等[77]在美国纽约州Adirondack洼地的研究中认为磷灰石中Lu-Hf体系的封闭温度为675~700 ℃。根据上述研究,David等[8]保守估计磷灰石中Lu-Hf体系的封闭温度为675~750 ℃。磷灰石Lu-Hf年龄能够表示其形成年龄,而且与母岩全岩Lu-Hf年龄具有一致性[78],因此可表示母岩的形成年龄,在一些母岩年龄较难测定时,磷灰石Lu-Hf为一种有效的解决途径。目前未见有碎屑磷灰石Lu-Hf体系应用于物源分析中的报道,但碎屑锆石Lu-Hf体系已被用于物源分析中[79,80],由于磷灰石Lu-Hf年龄可表征母岩年龄,对母岩时代的限定存在一定潜力,或在将来成为物源分析的手段之一。
此外磷灰石的Sm-Nd、O-S、O-C同位素能够反映其形成时的地质环境[81,82,83],主要应用于矿床成因分析、岩浆演化、变质及退变质作用、沉积条件再造等方面,在物源分析方面具有一定潜力,如Malusà等[12]对意大利波河河流沉积物的研究中,首次报道了磷灰石Sm-Nd同位素在物源分析当中的应用。
碎屑磷灰石作为初次沉积旋回的代表矿物,蕴藏着大量的源区信息,是非常重要的物源指针,随着分析技术的进步和精度的提高特别是原位分析技术的出现,碎屑磷灰石在物源分析中的作用日渐增强。
由于不同来源的磷灰石具有明显差异,因此可以利用沉积区的碎屑磷灰石进行物源判别。碎屑磷灰石在物源判别中的应用可归纳为以下几个方面:①元素地球化学方面: CART、REE参数二元图解投图和REE球粒陨石标准化配分模式;②年代学方面:AHe年龄、AFT年龄和U-Pb年龄及多法定年;③同位素方面:磷灰石的Sr-Nd同位素、Lu-Hf同位素等。
目前,国内在碎屑磷灰石物源判别的研究处于起步和探索阶段,并且存在一些问题亟需解决:①磷灰石的地球化学数据库仍需扩大,部分岩石特别是低级变质岩的磷灰石还需要开展大量的研究工作;②关于磷灰石U-Pb年龄的意义仍需要进一步确认;③部分类型岩石中的磷灰石存在成分分带,应确定一种方法避免成分分带对元素地球化学和年代学的研究带来影响。这些问题或成为碎屑磷灰石物源分析研究的新方向。
The authors have declared that no competing interests exist.
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陆源沉积岩物源分析对于古地理重建、古环境与古气候恢复、沉积盆地分析、沉积矿产预测、大地构造背景分析及盆山耦合研究等均具有重要意义。在大量文献调研的基础上，本文总结了沉积学方法、岩石学方法、重矿物方法、元素地球化学方法、地质年代学方法、粘土矿物学方法、化石及生标化合物方法及地球物理学方法等传统的物源分析方法及其研究进展；并介绍了近年来出现的磁性矿物学方法、矿物颗粒微形貌分析等物源分析新方法。由此展望了物源分析的发展趋势：随着新技术新方法的不断涌现，物源分析将从传统方法向现代测试技术的转化，从单一方法到多方法的综合运用，从单一学科走向多学科联合交叉，从定性分析向定量分析发展。
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Detrital rutile: A sediment provenance indicator [J].碎屑金红石: 沉积物源的一种指针 [J].
<p>摘要：近年来，碎屑金红石的研究已成为沉积物源区分析的一个新前沿。金红石的地球化学组成，尤其是Cr，Nb，Zr等微量元素的含量，对其母岩的形成条件和所经历的地质过程都具有重要的指示意义，同时，碎屑金红石在沉积、成岩过程中表现出极高的稳定性，因而是物源分析的理想指针矿物。首先介绍金红石的矿物学和地球化学基本性质，分析不同来源的金红石典型特征，重点阐述碎屑金红石在物源分析中运用的5个方面：①金红石重矿物比值；②金红石矿物化学成分Cr-Nb判别图解；③金红石Zr含量温度计；④金红石的U-Pb和(UTh)/He定年；⑤金红石Lu-Hf同位素。综合上述5个方面的物源分析研究，可以获取金红石的母岩类型、形成温度及后期所经历的热演化史等信息。碎屑金红石的物源研究处于起步和探索阶段，仍存在一些亟需解决的问题。</p>
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AbstractFission-track and (U–Th–Sm)/He thermochronology on apatites are radiometric dating methods that refer to thermal histories of rocks within the temperature range of 40°–125 °C. Their introduction into geological research contributed to the development of new concepts to interpreting time-temperature constraints and substantially improved the understanding of cooling processes within the uppermost crust. Present geological applications of apatite thermochronological methods include absolute dating of rocks and tectonic processes, investigation of denudation histories and long-term landscape evolution of various geological settings, and basin analysis.
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Over 700 apatite grains from a range of rock types have been analysed by laser-ablation microprobe ICPMS for 28 trace elements, to investigate the potential usefulness of apatite as an indicator mineral in mineral exploration. Apatites derived from different rock types have distinctive absolute and relative abundances of many trace elements (including rare-earth elements (REE), Sr, Y, Mn, Th), and chondrite-normalised trace-element patterns. The slope of chondrite-normalised REE patterns varies systematically from ultramafic through mafic/intermediate to highly fractionated granitoid rock types. (Ce/Yb) cn is very high in apatites from carbonatites and mantle-derived lherzolites (over 100 and over 200, respectively), while (Ce/Yb) cn values in apatites from granitic pegmatites are generally less than 1, reflecting both HREE enrichment and LREE depletion. Within a large suite of apatites from granitoid rocks, chemical composition is closely related to both the degree of fractionation and the oxidation state of the magma, two important parameters in determining the mineral potential of the magmatic system. Apatite can accept high levels of transition and chalcophile elements and As, making it feasible to recognise apatite associated with specific types of mineralisation. Multivariate statistical analysis has provided a user-friendly scheme to distinguish apatites from different rock types, based on contents of Sr, Y, Mn and total REE, the degree of LREE enrichment and the size of the Eu anomaly. The scheme can be used for the recognition of apatites from specific rock types or styles of mineralisation, so that the provenance of apatite grains in heavy mineral concentrates can be determined and used in geochemical exploration.
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Unraveling the growth of northern Tibet is crucial to understanding the geodynamic processes of the India-Eurasia collision, evaluating plateau uplift models and reconstructing associated paleoclimate history. However, pre-middle Miocene deformation history of northern Tibet remains poorly understood. We use detrital apatite fission track (detrital AFT) thermochronology of Mesozoic and Cenozoic sedimentary rocks from northern Qaidam basin to constrain the early growth of northern Tibet. Detrital AFT ages of the Mesozoic samples are younger than their depositional ages, indicating that the Mesozoic succession underwent two stages of exhumation after deep burial during 80–6162Ma and 54–4762Ma. Detrital AFT ages of the Cenozoic samples are older than their depositional ages and reveal that their source region experienced two periods of exhumation (peak ages in 86–5962Ma and 54–3662Ma). These results suggest that the northern Tibet successively experienced Late Cretaceous–early Paleocene and early–middle Eocene deformation. The Late Cretaceous–early Paleocene deformation implies that the extent of pre-collisional (India-Eurasia) deformation region in the plateau were much larger than previously known. The static detrital AFT peak ages (54–5162Ma) based on lag-time analysis for the Paleogene samples demonstrate the early Eocene deformation was a rapid and short-lived event, which was a far-field response to the India-Eurasia collision. Hence, we advocate synchronous deformation throughout the northern plateau at the collision time. Lag-time analysis results also demonstrate absence of Oligocene to early Miocene cooling ages and post-Eocene decreasing exhumation rates in the Cenozoic source regions. This suggests relatively quiescent tectonic settings in the Qilian Mountains during the Oligocene–early Miocene and agrees that the lateral strike-slip movement of the Altyn Tagh Fault was accommodated out of the plateau by the end of the early Miocene.
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Sandstone compositions result from a complex interplay between provenance and factors that operate during the sedimentation cycle. Accurate identification and discrimination of provenance depends on isolating provenance-sensitive features, and avoiding parameters that are influenced by other factors. Heavy mineral analysis offers a high-resolution approach to determination of sandstone provenance, because of the diversity of mineral species found in sandstones and because the factors affecting assemblages have been comprehensively evaluated. This paper presents the current understanding of the effects of processes operative during the sedimentation cycle. The original provenance signal may be overprinted by weathering at source prior to incorporation in the transport system; by mechanical breakdown during transport; by weathering during periods of alluvial storage on the floodplain; by hydraulic processes during transport and final deposition; by diagenesis during deep burial; and by weathering at outcrop. The most influential of these processes are hydraulics, which fractionates the relative abundance of minerals with different hydraulic behaviour, and burial diagenesis, which reduces mineral diversity through progressive dissolution of unstable mineral species. There is also evidence that weathering during alluvial storage plays a significant role. Two alternative, complementary approaches are recommended to identify provenance from heavy mineral data. The relative abundances of minerals with similar hydraulic and diagenetic behaviour are largely unaffected by processes operative during the sedimentation cycle, and utilize information gained from the entire heavy mineral suite. Determination of such ratios can be augmented by acquisition of varietal data, concentrating on the varieties shown by mineral types within the assemblage. A number of different varietal techniques are recommended, including optical differentiation of types based on colour, habit and internal structure, single-grain geochemical analysis, and single-grain geochronology.
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Routine low damage apatite U-Pb dating using laser ablation-multi collector-ICPMS [J].
[1] Apatite is a common U-bearing accessory mineral with a U-Pb closure temperature of 09080450000°C, making U-Pb dating of apatite a potentially valuable thermochronometer. However, its low U concentration and tendency to incorporate common lead has limited widespread application to destructive isotope dilution methods. We overcome previous limitations by using a Nu Plasma multicollector ICPMS with an attached short-pulse excimer laser, and by identifying two new matrix-matched reference apatites to correct for elemental fractionation: gem-quality 485 Myr old apatite from Madagascar which we independently characterized by ID-TIMS analysis, and 523.5 Ma apatite from the McClure Mountain syenite (source of the40Ar/39Ar reference MMhb). Common Pb is corrected using measured 204Pb isobarically corrected for Hg interference and a five-step iterative process using Stacey and Kramers' common Pb model. We accurately reproduce ages of numerous independently characterized apatites, regularly achieving precision of <2% (20303) by pooling as few as five 30 0204m spot analyses. Data quality in apatite with low U concentrations, low 206Pb/204Pb values (<09080430) and young ages (<09080475 Ma) is compromised by the goal of avoiding significant grain damage. Such limitations can be overcome by using spot sizes 65 0204m or greater, but at the expense of substantial grain damage. For single detrital apatite grains with ages of 090804500 Ma, precision of <4% (20303) was achieved by pooling 2 to 3 spots per grain. The accuracy of our detrital results is supported by a good age match with similar closure temperature 40Ar/39Ar detrital hornblende ages from the same sediment.
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Trace-element. Trace-element and Nd-isotope systematics in detrital apatite of the Po river catchment: Implications for provenance discrimination and the lag-time approach to detrital thermochronology [J]. |
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A study on crystal structure of collophanite [J].胶磷矿晶体结构研究 [J].
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Magmatic apatite: A powerful, yet deceptive mineral [J]. |
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Characteristics of the apatites of the volcanic complex in Lujiang-Zhongyang [J].庐枞地区中生代陆相火山杂岩中的磷灰石特征及其地质意义 [J]. |
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Phosphate minerals in terrestrial igneous and metamorphic rocks [M]∥ |
| [18] |
Apatite-monazite relations in the Kiirunavaara magnetite-apatite ore, northern Sweden [J].
The magnetite–apatite ores in the Kiruna area, northern Sweden, are generally considered to be of magmatic origin formed in a subvolcanic–volcanic environment during the early Proterozoic. They are thought to have crystallised from volatile-rich iron oxide magmas derived by immiscibility in calc-alkaline to slightly alkaline parental magmas. Three major morphological types of the magnetite–apatite ore (primary, brecciated, and banded) have been investigated for textural relations and mineral chemistry using transmitted light, back-scattered electron imaging (BSE), electron microprobe analysis (EMPA), and laser ablation–inductively coupled plasma-mass spectrometry (LA–ICPMS). In all three types, Th- and U-poor monazite is present as small inclusions in the apatite. Larger (up to 150 μm) recrystallised monazite grains, both along apatite grain boundaries and intergrown with magnetite and silicate minerals, are present in the brecciated and banded samples. Primary apatite grains, without monazite inclusions, are generally enriched in light rare earth elements (LREEs) together with Na and Si. Petrological and mineralogical evidence suggest that the Kiruna magnetite–apatite ore experienced successive stages of fluid–rock interaction. The first stage occurred under high-temperature conditions (700–800 °C) shortly after emplacement and crystallisation of the ore magmas and involved concentrated, probably Cl-dominated brines expelled from the magma. This fluid is held to be responsible for the nucleation of the numerous small monazite inclusions within the apatite due to high-temperature leaching of Na and Si, while the LREEs were concentrated in the monazite. The large monazite grains in the brecciated and banded samples are proposed to be the product of recrystallisation from the much smaller monazite inclusions. During greenschist-facies metamorphism ( T=300–400 °C), fluids from the surrounding country rock caused strong (LREE+Na+Si) depletion along apatite grain boundaries and cracks in the apatite. LREEs were either redeposited as monazite grains along apatite grain boundaries or were flushed out of the ore. This fluid interaction also introduced the silicate components responsible for the interstitial formation of allanite, talc, tremolite, chlorite, serpentine, muscovite, quartz, and carbonates along apatite grain boundaries.
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| [19] |
Apatite chemical composition by electron microprobe and laser-blation inductively coupled plasma spectrometry, as a probe into granite petrogenesis [J].
Major, minor, and trace element abundances in apatites from various I- and S-type (igneous and sedimentary) granites of the Lachlan Fold Belt have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometer. The results show that apatite can accommodate many minor and trace elements, whose concentrations and ratios are relatively sensitive to factors controlling many of the fundamental differences between I- and S-type granites. Apatites from S-type granites generally have higher F but lower Cl contents than those from I-type granites, which is ascribed mainly to the loss of Cl during the weathering processes forming the source rocks of S-type granites, although fractional crystallisation can cause significant enrichment in F as well. High Mn and Fe contents in apatites from S-type granites, and high S and As abundances in apatites from mafic I-type granites, result from different oxygen fugacities and degrees of Al saturation (or aluminosity) between metaluminous mafic I-type magmas and peraluminous S-type and felsic I-type magmas. There are systematic and distinctive differences in absolute rare-earth element (REE) abundances, REE distribution patterns, and element ratios (e.g., La/Y, Sm/Nd, etc.) between apatites from different types of granite. The strong Eu depletion that characterises apatites from S- and felsic I-type granites is interpreted here to be a result of the uniqueness of crystal chemistry of apatite and high Eu /Eu ratios in S-type and felsic I-type magmas, which are more reduced and peraluminous than mafic I-type magmas. Strong REE (La to Eu) and Th enrichment in apatites from mafic I-type granites and marked Nd depletion in apatites from most S-type and felsic I-type granites are caused by the precipitation and fractionation of monazite in the parental magmas of the latter rocks. Substitution mechanisms are responsible for high Na in apatites from S-type and felsic I-type granites, and for high Si in apatites from mafic I-type granites, and may also have important effects on REE partitioning between apatite and melt. Thus, apatite chemistry can be used as an excellent indicator of granite petrogenesis. The results have important implications for identifying different types of granite and are potentially significant for determining the provenance of sedimentary rocks.
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| [20] |
U and Th zonation in apatite observed by laser ablation ICPMS and implications for the(U-Th)/He system [J].
A laser-ablation inductively-coupled plasma mass spectrometry technique was developed to measure U, Th, and Ce zonation in polished sections of apatite for assessing the consequences of parent zonation for (U–Th)/He thermochronometry. The technique produces concentration maps with an averaging length-scale of 6520 μm, comparable to the α-stopping distance, and a precision of 655% down to few ppm concentration levels. A model was developed to transform the measured concentration distribution into a simplified representation for use in spherical-geometry He production–diffusion models. To illustrate these methods, 30 sections of apatite from a single granite (GC863) were mapped. Every analyzed apatite from GC863 is zoned, with most grains having variable thickness rims and terminations that are enriched in U and Th by about a factor of three over the grain cores. Parent zonation has three independent effects on (U–Th)/He He ages: it influences the α ejection correction, the 4He concentration profile which governs diffusive loss, and, via radiation damage trap accumulation, spatial variability of diffusivity within the crystal. If the observed zonation is typical of the apatite population in GC863, use of the standard homogenous α ejection correction would cause He ages to be on average 3% too young, and with a large amount of grain-to-grain variability (9% too young in the most rim-enriched case to 6% too old in a core-enriched case). Independent of the ejection correction, the concentration profile modifies the effective closure temperature of the apatites by placing more (or less) 4He near the grain edge. The parent zonation in GC863 apatites causes closure temperatures to range from four degrees lower (rim-enriched case) to two degrees higher (core-enriched case) than applies in the homogenous case. Alpha ejection and concentration profile effects on He age are additive and of the same sense. In the case of typical grains in GC863 cooled between 1 and 10 °C/Ma, the two effects are roughly equal in magnitude. The effects of intracrystalline variations in radiation damage trap accumulation become apparent at slow cooling rates (1 °C/Ma). For example, in rim-enriched GC863 grains cooled at 1 °C/Ma, preferential accumulation of radiation damage traps near the grain rim almost compensates for the higher loss rate expected of 4He also located preferentially near the rim. Under some circumstances strong rim-enrichment may actually increase the effective closure temperature of an apatite. Zonation at the level observed in GC863 modifies the 4He/ 3He spectra substantially from that expected from a uniform distribution. Measured 4He/ 3He spectra are strikingly similar to predictions based on the mapped eU distributions of the very same crystals, supporting the overall validity of the analytical and interpretive approach presented here. The magnitude and style of U, Th zonation documented in GC863 is one possible source of frequently observed over-dispersion of apatite (U–Th)/He ages as well as anomalous 4He/ 3He spectra.
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| [21] |
Interpreting data dispersion and "inverted" dates in apatite(U-Th)/He and fission track datasets: An example from the US midcontinent [J].
New apatite (U–Th)/He (AHe) and apatite fission-track (AFT) data were acquired for cratonic basement samples from an 80 m span of drillcore in northeastern Kansas. The short depth interval over which the samples were collected indicates that they should have undergone thermal histories that would be indistinguishable using low temperature thermochronometry techniques. Individual AHe dates from four samples range from 99 to 464 Ma. Three samples yield dates <300 Ma that display a correlation with apatite eU (9–34 ppm) and a weaker correlation with grain size. eU concentration maps of apatites from these samples reveal low to moderate zonation in eU. Results for a fourth sample are characterized by dates >300 Ma, higher eU (39–113 ppm), and substantial data dispersion uncorrelated with eU and grain size. These apatites have strong and variable eU zonation. AFT dates for five samples range from 242 to 291 Ma. The sample with the highest eU apatites and oldest AHe dates yields the youngest AFT results. These results are “inverted”, with AHe dates distinctly older than the corresponding AFT date. We explore both the causes of data dispersion and the overall compatibility of this cratonic dataset. We find that geologically reasonable thermal histories can (1) explain the distribution of the moderate eU AHe data when accounting for the influence of radiation damage, grain size, and eU zonation on apatite He diffusivity, (2) reproduce the observed dispersion in the high eU AHe data when using a viable range of eU zonation and grain size, and (3) explain the AFT data for the same samples. The AHe and AFT data are mutually consistent, and viable thermal histories successfully predict the observed pattern of older AHe than AFT dates for the high eU apatites. Together these results suggest that appropriately accounting for the known controls on apatite He diffusivity can explain the observed dispersion and “inverted” AHe and AFT results in some thermochronometry datasets. A range of AHe dates should be especially common in cratonic data, because small differences in apatite He diffusivity are amplified by the thermal histories that typify cratonic settings. We use these results to develop some guidelines for interpreting dispersed AHe datasets. First, date–eU and date–grain size correlations should be evaluated, and if these patterns occur they can be used to better resolve the thermal history. Second, for samples that yield inexplicably large dispersion of AHe dates uncorrelated with eU and crystal size, the appropriate strategy is either to reject these samples from the suite used for thermal history interpretation or to acquire additional data to help decipher the significance of the age distribution.
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| [22] |
Is apatite U-Th zonation information necessary for accurate interpretation of apatite (U-Th)/He thermochronometry data [J].
New U, Th and Ce concentration maps were acquired by LA-ICPMS for 70 apatites from 18 cratonic basement samples from the Canadian shield to characterize the nature and variability in apatite U–Th zonation. All apatites are zoned in effective U concentration (eU), with 80% exhibiting modest zoning that varies from a factor of 651.2 to 652.4. Zonation patterns include those with a general eU decrease from core to rim (6525%), a core to rim eU increase (6535%), and patchy or irregularly shaped eU distributions (6540%). Most samples consist of individual apatites with markedly different and opposing eU profiles. Cathodoluminescence (CL) images were obtained for 258 apatites in 25 samples. Comparison of eU and CL patterns reveals no consistent relationships, suggesting that CL is not a reliable proxy for apatite eU zonation. We explore the implications of eU zonation for the interpretation of apatite (U–Th)/He (AHe) data by comparing the age predictions for representative and endmember apatite eU profiles with those for unzoned apatites. We focus on thermal histories that should magnify eU zonation effects, including slow monotonic cooling, extended He partial retention zone (HePRZ) residence, and protracted reheating and cooling. Application of incorrect α-ejection correction (FT) factors, different He concentration gradients, and variable intracrystalline retentivity due to heterogeneous radiation damage may cause the AHe dates for zoned and unzoned apatites to differ. In our dataset, the magnitude of the FT effect is <1.5% for most samples. The He diffusion gradient and heterogeneous radiation damage effects cause apatites with eU enriched cores to yield AHe dates equal to or older than unzoned grains, with the opposite true for apatites with eU enriched rims. For monotonic cooling rates as slow as 0.1°C/Myr, apatites of typical eU zonation exhibit a <1°C difference in effective closure temperature from equivalent unzoned grains. The difference in HePRZ temperature at 50% of an 150Myr isothermal holding time is <1.4°C for typically zoned apatites. For most reheating simulations considered here, age deviations between zoned and unzoned apatites are not significant, and reach maximum differences of 6510% for peak temperatures that induce partial He loss from the apatites. The age dispersion caused by zonation is comparable to that induced by grain size variations, but is considerably less than what can be caused by differences in mean eU and associated radiation damage for certain histories. By simulating zoned apatite suites from representative and endmember samples we find that eU zoning adds modest age dispersion to most samples. The commonly opposing eU profiles for individual apatites in most samples have different effects on the predicted age, and partially cancel each other out to reduce the predicted age difference at the sample level. Higher predicted age differences between zoned and unzoned samples generally correlate with greater sample scatter. The age deviations generally fall within the 6515% uncertainty range that we commonly apply for sample AHe dates. Except in unusual circumstances, it appears unlikely that the unzoned apatite assumption will lead to misinterpretation of AHe datasets, thus precluding the need to routinely acquire apatite eU zonation information as part of AHe dating studies.
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| [23] |
LA-ICP-MS depth profile analysis of apatite: Protocol and implications for(U-Th)/He thermochronometry [J].
Heterogeneous concentrations of α-producing nuclides in apatite have been recognized through a variety of methods. The presence of zonation in apatite complicates both traditional α-ejection corrections and diffusive models, both of which operate under the assumption of homogeneous concentrations. In this work we develop a method for measuring radial concentration profiles of 238U and 232Th in apatite by laser ablation ICP-MS depth profiling. We then focus on one application of this method, removing bias introduced by applying inappropriate α-ejection corrections. Formal treatment of laser ablation ICP-MS depth profile calibration for apatite includes construction and calibration of matrix-matched standards and quantification of rates of elemental fractionation. From this we conclude that matrix-matched standards provide more robust monitors of fractionation rate and concentrations than doped silicate glass standards. We apply laser ablation ICP-MS depth profiling to apatites from three unknown populations and small, intact crystals of Durango fluorapatite. Accurate and reproducible Durango apatite dates suggest that prolonged exposure to laser drilling does not impact cooling ages. Intracrystalline concentrations vary by at least a factor of 2 in the majority of the samples analyzed, but concentration variation only exceeds 5x in 5 grains and 10x in 1 out of the 63 grains analyzed. Modeling of synthetic concentration profiles suggests that for concentration variations of 2x and 10x individual homogeneous versus zonation dependent α-ejection corrections could lead to age bias of >5% and >20%, respectively. However, models based on measured concentration profiles only generated biases exceeding 5% in 13 of the 63 cases modeled. Application of zonation dependent α-ejection corrections did not significantly reduce the age dispersion present in any of the populations studied. This suggests that factors beyond homogeneous α-ejection corrections are the dominant source of overdispersion in apatite (U–Th)/He cooling ages.
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| [24] |
Apatite(U-Th-Sm)/He thermochronology of rapidly cooled samples: The effect of He implantation [J].
Apatite (U–Th–Sm)/He (AHe) thermochronology is increasingly used for reconstructing geodynamic processes of the upper crust and the surface. Results of AHe thermochronology, however, are often in conflict with apatite fission track (AFT) thermochronology, yielding an inverted age-relationship with AHe dates older than AFT dates of the same samples. This effect is mainly explained by radiation damage of apatite, either impeding He diffusion or causing non-thermal annealing of fission tracks. So far, systematic age inversions have only been described for old and slowly cooled terranes, whereas for young and rapidly cooled samples ‘too old’ AHe dates are usually explained by the presence of undetected U and/or Th-rich micro-inclusions. We report apatite (U–Th–Sm)/He results for rapidly cooled volcanogenic samples deposited in a deep ocean environment with a relatively simple post-depositional thermal history. Robust age constraints are provided independently through sample biostratigraphy. All studied apatites have low U contents (< 502ppm on average). While AFT dates are largely in agreement with deposition ages, most AHe dates are too old. For leg 43, where deposition age of sampled sediment is 26.5–29.502Ma, alpha-corrected average AHe dates are up to 4502Ma, indicating overestimations of AHe dates up to 50%. This is explained by He implantation from surrounding host U–Th rich sedimentary components and it is shown that AHe dates can be “corrected” by mechanically abrading the outer part of grains. We recommend that particularly for low U–Th-apatites the possibility of He implantation should be carefully checked before considering the degree to which the alpha-ejection correction should be applied.
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| [25] |
Geochemistry of apatite from HP-UHP metamorphic belt in southwestern Tianshan Mountains, Xinjiang [J].新疆西南天山高压—超高压变质带中磷灰石的地球化学研究 [J]. |
| [26] |
Rare Earth Elements(REE) geochemistry of apatites in HP-UHP metamorphic rocks from Chinese Continental Scientific Drilling(CCSD) project and their implications [J].CCSD HP-UHP变质岩中磷灰石稀土元素(REE)地球化学及其示踪意义 [J].
磷灰石是一种能在UHP变质峰期稳定存在并富含稀土元素(BEE)的常见副矿物,其BEE组成变化可以对变质过程进行地球化学示踪.本文利用激光剥蚀等离子光谱仪(LA-ICP-MS)对中国大陆科学钻探(CCSD)钻井中及其附近出露的不同变质程度的HP-UHP变质岩(榴辉岩、角闪(片)岩和片麻岩)中的磷灰石进行了REE组成原位测定,结果显示不同围岩中磷灰石的BEE组成特征及其相关系数变化很大,其球粒陨石标准化配分曲线可以分为3大类:Ⅰ.轻稀土(LBEE)富集型,其REE总量(∑REE)很高,可达n×1000×10-6;Ⅱ.中稀土(MREE)富集型,其(La/Sm)N＜1,Eu异常变化较大;Ⅲ.重稀土(HREE)富集型,其配分曲线呈明显的左倾形式,∑BEE总量很低,仅为9.228×10-6,且具明显的Eu负异常.磷灰石颗粒原位分析显示从边部到中心∑LREE有逐渐升高的趋势,表明了在俯冲折返的过程发生过短时增温作用,并极有可能发生过部分熔融.部分熔融过程中磷灰石中的LREE将与其它大离子半径元素一起优先释放.
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| [27] |
Apatite in igneous systems [J]. |
| [28] |
Rare earth element systematics of carbonatitic fluorapatites, and their significance for carbonatite magma evolution [J].
Magmatic fluorapatites of five African carbonatite complexes were analyzed for rare-earth (REE) and trace elements by electron microprobe and high-resolution synchrotron micro-XRF to explore the fluorapatite composition during different stages of carbonatite magma evolution. Early crystallized fluorapatites have La concentrations mostly below 1,50002ppm and low ΣREE. They display convex-upward shaped REE patterns with (La/Nd) cn ≤1 and low (La/Yb) cn ratios 1 and (La/Yb) cn generally above 100, and have La up to 102wt% at a high ΣREE. Model calculations with the fractionating mineral assemblage fluorapatite+calcite±clinopyroxene suggest REE distribution coefficients for fluorapatite/carbonatite melt with a positive slope throughout from La to Lu, in order to meet the relationships observed in the natural fluorapatites. The calculations oppose closed system conditions of magma fractionation along the liquid lines of descent, but suggest periods of instantaneous fluorapatite crystallization. Fluorapatite trace element characteristics are therefore thought to be indicative for carbonatite evolution, and can reflect the relative degree of magma fractionation. We suggest that the (Eu/Eu*) cn and Y evolution in the fluorapatites is a manifestation of an aqueous fluid immiscibly coexisting with the carbonatite magma from early evolution on, which is able to continuously extract divalent Eu and Y from the carbonatite magma.
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| [29] |
REE content and distribution in apatite and its geological tracing significance [J].磷灰石的稀土组成及其示踪意义 [J].
磷灰石是一种分布很普遍的含稀土矿物.作者测定并收集了产于各类岩石及某些矿石中磷灰石的稀土元素组成,绘制了磷灰石的稀土元素球粒陨石标准化分布模式的8种典型代表.据此,磷灰石可以作为一种示踪矿物来应用.
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| [30] |
Microstructure of SiO2-Al2O3-CaOP2O5-K2 O-F-glass ceramics needlelike versus isometric morphology of apatite crystals [J]. |
| [31] |
Some characteristics of igneous apatite [J].火成岩中副矿物磷灰石的某些特征 [J].
磷灰石[Ca_(10)(PO_4)_6(Cl,F,OH)_2]是火成岩中最普遍的副矿物之一。它在岩石中含量的变化、结晶的习性、及其对其他硅酸盐矿物析出的先后顺序、附生元素的特征等,无论对于了解岩浆的成分及其演化特性、或阐明矿化与侵入体的成因关系及不同杂岩体之间的对比研究方面,都将提供很有价值的材料。本文旨在作一概略的初步报导。
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| [32] |
Rare earth element features of apatite separated from the Heiyingshan high-grade iron deposit, Inner Mongolia [J].内蒙古黑鹰山富铁矿床磷灰石稀土元素地球化学特征 [J].
笔者首次对内蒙古西部黑鹰山富铁矿床两类铁矿石磷灰石进行了稀土元素含量分析,致密块状铁矿石6件磷灰石样品ΣREE含量变化范围为(14776.86~21313.18)×10-6,LREE/HREE比值为8.31~9.18,δEu为0.37~0.40。相比之下,脉状铁矿石2件磷灰石样品ΣREE含量变化范围为(18143.05~20665.82)×10-6,LREE/HREE比值为9.03~9.18,δEu为0.39。所有8件磷灰石稀土元素分配型式均为一组向右倾斜,并且具有明显铕负异常的曲线。黑鹰山铁矿床中磷灰石的最显著特点是稀土元素含量明显高于国内外同类铁矿床磷灰石,为我国宁芜铁矿床和瑞典基鲁纳铁矿床磷灰石的4~10倍。根据磷灰石样品的地球化学特征,并且结合其他岩(矿)相学特征和钐-钕同位素数据,可以推测,磷灰石的形成作用与海西早期构造-岩浆活动有关,富铁矿床很可能是富碱岩浆热液流体喷溢或上侵定位的产物,成矿(岩)物质主要来自以幔源物质为主的壳-幔混源岩浆房。
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| [33] |
A LA-ICP-MS study of apatite from the Taocun magnetite-apatite deposit, Ningwu Basin [J].宁芜盆地陶村铁矿床磷灰石的LA-ICP-MS研究 [J].
宁芜盆地是长江中下游成矿带中的重要矿集区之一，磷灰石是该区各矿床中的标志性矿物之一。本文以宁芜玢岩铁矿典型代表之一的陶村铁矿床为研究对象，利用激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)微区分析新技术和电子探针分析方法对该矿床中辉石闪长玢岩中的磷灰石（Ap-I）、浸染状磁铁矿矿石中的磷灰石（Ap-D）和脉状磁铁矿矿石中的磷灰石（Ap-V）进行了微量元素和主量元素组成的研究。其结果表明辉石闪长玢岩中的磷灰石（Ap-I）和两种类型矿石中磷灰石（Ap-D和Ap-V）的主要元素成分变化范围都很小，均为氟磷灰石，并含有少量的S和Cl。其中Ap-I含有较高的Na、Mg、Si、V、Mn、Fe、Ga、Ge 、Sr、Y、Zr、Ba、REE、Pb、Th和U。Ap-D中除了含有较高的Na、Mg、Si、V、Mn、Fe、Ga、Ge 、Sr、Y、Zr、Ba、REE、Pb、Th和U之外，还含有Al、Sc、Cr、Ni和Cu。Ap-V与Ap-D不同的是Al、Sc、Cr、Ni和Cu的含量较低，只有少数分析点值高于仪器的检测限。岩浆岩中的磷灰石（Ap-I）和两种类型矿石中磷灰石（Ap-D和Ap-V）中Zr、Y、Lu、Yb、Mn和δEu之间的演变关系以及稀土元素分配形式表明陶村铁矿床的成矿热液可能来源于辉石闪长玢岩，从浸染状矿化到脉状矿化，成矿热液的氧逸度升高，成矿热液中的REE等微量元素的含量降低。陶村铁矿床为与辉石闪长玢岩密切相关的岩浆热液型矿床。通过将陶村铁矿床矿石中磷灰石（Ap-D和Ap-V）的F、Cl、S和REE的组成与Kiruna型矿床和IOCG型矿床进行对比发现，他们之间存在明显差异，表明以陶村铁矿床为代表的宁芜玢岩型铁矿床既不属于Kiruna型矿床也不属于IOCG型矿床。
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| [34] |
The genesis of the Zhaoanzhuang Fe oxide deposit in Wuyang region of Henan Province: Insights from magnetite and apatite [J].河南舞阳赵案庄铁矿床成因:来自磁铁矿和磷灰石的矿物学证据 [J].
As a part of the Wuyang iron deposit, the Zhaoanzhuang Fe oxide deposit is located at the southern margin of the North China Craton and occurs in ultramafic rocks which intruded into the Zhaoanzhuang Formation of the Early Paleoproterozoic Taihua Group. The deposit is closely related to the ultramafic rocks both spatially and temporally, and they have similar mineral assemblages, suggesting similar origin. The ores have classic sideronitic texture. Magnetites from both the ores and rocks are characterized by high V (1458×10~2524×10), Mg (2502×10~4674×10) and low Ti (395×10~3186×10), Cr (3.30×10~66.1×10), Ni (93.0×10~176×10), Mn (259×10~937×10) contents. Apatites from both the ores and ultramafic rocks are present as equigranular coarse grains, occurring interstitially between magnetite grains. They have high ∑REE (4983×10~7038×10) and F (2.69%~3.52%) contents as well as high F/Cl (21.5~78.8) and LREE/HREE ratios ((La/Yb)=28~45) without Ce depletion. It is indicated that magnetite and apatite crystallized in magma with hydrothermal overprinting. Furthermore, the trace elemental contents of the parental magma calculated using the compositions of apatite indicate that the magma underwent crustal contamination. And the olivine of Zhaoanzhuang ultramafic rock is high Mg and low Cr and Ni, indicating olivine crystallized in volatile-rich melts. In addition, a lot of carbonate minerals in ores also show the addition of CO from the wall rock into the magma, which increased oxygen fugacity of the magma and enhanced the crystallization of magnetite instead of ilmenite. Therefore, the formation of low-Ti magnetite could be due to both high oxygen fugacity and low-Ti magma source. And the Zhaoanzhuang Fe oxide deposit, classified into magma ores, are genetically related to the ultramafic rocks. The parental magma was contaminated with CO-rich fluid.
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| [35] |
REE geochemical characteristics of apatite, sphene and zircon from alkaline rocks [J].
碱性岩中磷灰石、榍石和锆石的稀土元素地球化学特征 [J].URL 摘要
碱性岩的副矿物磷灰石和榍石是岩体中稀土元素的主要载体矿物。它们的稀土分布模式与母岩相同,向右陡倾斜,磷灰石的Eu负异常明显,榍石具Ce正异常,锆石呈大体对称“V”形模式,Eu负异常最大。与花岗岩中同一矿物对比,上述矿物都体现了幔源碱性岩浆轻稀土富集,Eu亏损小的特点。磷灰石、榍石和锆石相应富集了母岩中的轻、中、重稀土元素,稀土元素的这种置换行为主要是矿物晶体化学性质控制的。
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| [36] |
A peculiar composite M-and W-type REE tetrad effect: Evidence from the Shuiquangou alkaline syenite complex, Hebei Province, China [J].
一种特殊的“M”与“W”复合型稀土元素四分组效应:以水泉沟碱性正长岩为例 [J].
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| [37] |
Trace element and rare earth element characteristics of apatite from Abagong iron deposit in Altay City, Xinjiang [J].
新疆阿勒泰市阿巴宫铁矿磷灰石微量和稀土元素特征及矿床成因探讨 [J].
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| [38] |
Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types [J].
An investigation of the content and distribution of REE in apatite and magnetite in the iron ores of Kiruna type and some other iron ores is presented. REE in apatite and magnetite in different ore types show characteristic patterns which are related to different modes of formation of the ores.The magnetite-apatite iron ores of the world can be divided into two types: (a) Kiruna iron ores proper which occur in volcanic rocks, and (b) iron ores connected with deuteric processes and/or related to intrusive rocks. Apatite of the Kiruna ores proper in Fennoscandia (e.g. Kiirunavaara, Malmberget and Grangesberg) shows a common pattern with 2000-7000 ppm RRE, a weak to moderate LREE/HREE fractionation and negative Eu anomalies. In the Kiruna area, apatite of the main, P-poor ores and of the later, hydrothermal-exhalative P-rich ores, have the same REE distribution which indicates a common source. There is a similar REE distribution in magnetite-apatite trachytic-rhyodacitic host rock which confirms a close magmatic relationship. Apatite in phosphorites (such as the Paleoproterozoic Palang deposit in northern Sweden) has a different composition (< 1000 ppm REE with Ce depletion) which excludes a sedimentary origin of the Kiruna apatite.Apatite in other volcanogenic magnetite-apatite ores outside Fennoscandia differ by a stronger LREE/HREE fractionation and by a medium to large Eu depletion, partly indicating a relationship to alkaline intrusions. The Avnik apatite, Turkey, shows a weak differentiation in combination with a pronounced negative Eu anomaly, indicating provenance from silicic magmatic sources.The REE pattern of apatite in the deuteric-hydrothermal apatite-bearing iron ores is in general similar to that of apatite in the Kiruna iron ores proper. The similarity indicates a common process of formation for both ore types.The apatite-iron ores of the Kiruna type proper were formed by a late-magmatic differentiation. The ores of the Kiruna area are, in similarity with some other magnetite-apatite ores, emplaced along regional fracture-fault lines and close to an older basement. In general the REE pattern of apatite in the different deposits shows an affinity to alkaline or sub-alkaline magmas, indicating a rifting environment. The alkaline, trachytic volcanics hosting the Kiruna ores in northern Sweden are clearly related to an extensional setting where rifting was important. A probable source for this large-scale ore-forming process was partial melting of deep-seated rocks. The ores evolved in an intracontinental setting with magma generation caused by underplating of older crust.The process giving rise to magnetite-apatite ores of the Kiruna type has occurred during the time span from Paleoproterozoic to Tertiary. The Proterozoic ores occur mainly in cratonized areas, whereas the younger ones occur in fold belts. The amount of ore formed in post-Proterozoic time is as large as that formed in Proterozoic time.
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| [39] |
Tetrad effect of REE in apatites from pegmatite NO.3, Altay, Xinjiang and its implications [J].新疆阿尔泰可可托海3号伟晶岩脉磷灰石矿物中稀土元素“四分组效应”及其意义 [J].
新疆阿尔泰可可托海3号伟晶岩脉磷灰石矿物中稀土元素(REE)和其他微量元素的ICP-MS分析结果表明,Y/Ho、Zr/Hf和Nb/Ta明显偏离球粒陨石中对应的比值,并存在显著的REE“四分组效应”.REE“四分组效应”量化特征参数TE3.4主要与Y/Ho、Nb/Ta分异程度有关,与δEu负异常演化程度相一致.锰铝榴石也呈现REE“四分组效应”和Y/Ho、Nb/Ta显著分异,指示REE“四分组效应”是形成伟晶岩熔体的一个基本特征,并不是由富LREE矿物(如独居石)和富HREE矿物(如石榴子石)结晶引起的残余熔体REE含量的异常变化,其机制可能是富F、B和P的过铝质熔体与含水流体间相互作用.REE在流体相/熔体相的分配受温度、压力和流体相组成复合控制的综合结果.
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| [40] |
In situ LA-ICP-MS analyses of apatites from carbonatites in western Shandong Province: Implications for petrogenesis [J].鲁西碳酸岩中磷灰石的原位激光探针分析及其成岩意义 [J].
以鲁西雪野和八陡碳酸岩中的磷灰石为对象,运用EMPA和LA-ICP-MS技术,分别测定 了它们的主量与微量元素组成,并据此讨论了它们的成岩意义。研究结果表明,这些磷灰石富F(=1.07%～2.74%)贫Cl(1,(La/Yb)_N比值多数在100以上,与世界其他地区典型碳酸岩中的磷灰石相比铕负异常相对更明显,表明其寄主碳 酸岩浆经历一定程度的分异演化。雪野较八陡碳酸岩中磷灰石含更高的F、Sr和∑REE含量及(La/Yb)_N比值,说明其寄主岩浆的演化程度更高。
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| [41] |
Mineralogy and trace elemental geochemistry of apatite in Sulu eclogites [J].苏鲁榴辉岩中磷灰石的矿物学和微量元素地球化学 [J].
Apatite is a common accessory mineral in HP-UHP eclogites. It is an excellent witness of the physical and chemical process associated with the formation, subduction and exhumation of HP-UHP rocks. To further reveal the physico-chemical variations recorded in apatite grains, detailed petrography and in-situ LA-ICP-MS trace element analysis were conducted on apatites in eclogites from CCSD main hole and an outcrop sample from the Qinglongshan. Apatites were inferred to recrystallize mostly during UHP metamorphic stage, and are rich in LREE and Sr if they did not experience significant retrograde metamorphism. In contrast, LREE and Sr were evidently decreased in the rim of apatites that had seen the retrograde fluids due to more soluble and mobile of these elements in retrograde fluids. Slightly increase of HREE were associated with short heating and breakdown of garnet during retrogration, the negative anomaly of Eu could have resulted from the growth of plagioclase and decrease in oxygen fugacity during retrogration. Integrated previous studies of “exsolution lamellae” in apatites, we propose that monazite “exsolution lamellae” in eclogitic apatites were probably represented the product of metasomatic interaction between apatite grains and retrograde fluids, which may be HO-NaCl-and silicate-bearing solutions. Sulfide lamellae in apatites were probably caused not only by the decrease of oxygen fugacity, but also by short heating effect during retrograde reactions. The redox state of metamorphic fluids in UHP metamorphic rocks may have experienced complicated variation from oxidation →reduction →oxidation during prograde-peak →early retrograde →amphibolitic faciesstage.
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| [42] |
REEs geochemistry of Doushantuo phosphorites and modification during post sedimentary stages in Weng'an area, South China [J].贵州瓮安陡山沱组磷块岩稀土元素地球化学特征与沉积期后变化 [J].
贵州瓮安陡山沱组磷块岩保存了可能是全球最早的后生动物化石 (瓮安动物群 ),对于瓮安动物群出现过程中的古海洋环境重建具有重要科学意义。但必须对成岩后生作用对磷块岩中的稀土元素改造进行评估。通过对贵州瓮安陡山沱组磷块岩的磷质碎屑、磷质和白云质胶结物、磷条带和泥条带等的稀土元素地球化学特征研究,确定沉积期后变化对稀土元素的改造影响不大。上矿层磷块岩沉积期形成的磷质碎屑、成岩期形成的白云质和磷质胶结物具相同的稀土元素配分模式,暗示了沉积期后的改造作用对瓮安陡山沱组磷块岩保存的原生沉积信息影响不大。瓮安陡山沱组磷块岩具有显著的重稀土亏损特征。磷块岩的磷质和白云质胶结物、伴生磷质碎屑、强风化磷块岩相近的ErN/LuN 比值,表明沉积期后的改造作用不是重稀土元素亏损的主要原因。磷块岩的ErN/LuN、LaN/NdN 与Ce/Ce 间的相关性,表明越氧化的沉积环境中,轻和重稀土元素亏损越强。
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| [43] |
Rare earth elements geochemistry and genesis of Xinhua large size phosphorite deposit in western Guizhou [J].
黔西新华大型磷矿磷块岩稀土元素地球化学及其成因意义 [J].
利用ICP_MS测试方法系统分析了黔西织金新华磷矿磷块岩的稀土元素组成,同时还测定了贵州遵义和湖南张家界等华南下寒武统黑色岩系中磷块岩的稀土元素含量。结果显示①新华磷块岩稀土元素总量(ΣREE)较高,变化较大,为164.23×10-6～1395.01×10-6,平均642.54×10-6,轻重稀土分异明显,LREE/HREE值为5.04～6.52,平均5.69,而华南其他地区磷块岩的ΣREE和LREE/HREE分别为156.69×10-6～637.41×10-6(平均431.75×10-6)和3.17～6.95(平均4.37);②新华磷块岩的δCe为0.26～0.53,华南其他地区磷块岩的δC
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| [44] |
Rare Earth Element Geochemistry [M]. |
| [45] |
Discovery of pyrrhotite exsolution in apatite [J].磷灰石中磁黄铁矿出溶结构的发现 [J].
中国东部苏鲁地区(江苏赣榆)出露大理岩-榴辉岩块体,其菱镁矿大理岩中保存的白云石分解结构表明地壳物质俯冲深度达到-200公里。在与该大理岩共生的榴辉岩中,我们发现了磷灰石的磁黄铁矿出溶结构。磷灰石是该榴辉岩的主要副矿物,其自形程度较高,与石榴石共生。样品中几乎所有磷灰石均发育出溶结构,至少存在两组相互垂直的出溶棒,它们各自严格沿同一个方向分布。出溶棒形状规则,宽度相近(<1μm),但长度变化大(5-50μm)。利用高分辨能谱仪测定其能谱,结果表明,出溶棒主要由Fe和S两种元素组成,但不能准确地确定其Fe/S比值。我们把这种出溶棒初步确定为磁黄铁矿(Fe1-xS)。磷灰石由于含大量稀土元素和挥发性组分如OH、F、Cl等以及我们所观察到的S,它的深循环因此可能对地球的水、硫以及其它挥发性组分的全球平衡具有重要影响。本文报道的磷灰石中磁黄铁矿出溶结构为深入探讨这个基本科学问题提供了一个新的突破口。
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| [46] |
Discovery of apatite with copper-bearing pyrrhotite exsolution in an eclogite from Rongcheng, eastern Shandong Province [J].胶东荣成榴辉岩中含铜磁黄铁矿出溶结构的磷灰石的发现及其意义 [J].
在苏鲁超高压变质带东北部胶东荣成地区的退变金红石榴辉岩中,我们发现了具含铜磁黄铁矿出溶结构的磷灰石。磷灰石在该榴辉岩中含量较高(≈5%),多为不规则形状,颗粒大小不一,粗大者可达1．2mm×0．6mm。样品中几乎所有的磷灰石均发育出溶结构,出溶棒可能分为相互垂直的两组,各自分别沿同一方向分布,出溶棒密度大,形状规则,宽度相似,长度最长可达0．1mm。在扫描电子显微镜下,利用X射线能谱仪测定出溶棒主要由Fe、Cu和S三种元素组成。由于很难准确确定三者的比例,暂将其定为含铜磁黄铁矿((Fe_(1-x)Cu_x)S)。报道的磷灰石含铜磁黄铁矿出溶结构,与江苏赣榆地区磷灰石的磁黄铁矿出溶结构,同产于苏鲁超高压变质带中,具有可对比性；磷灰石中Cu、Fe的溶解度可能是温压条件的函数；因此进一步精确研究磷灰石中这些出溶结构的成分和成因,将为深入探讨苏鲁超高压变质带不同地体变质条件、成因的差异及俯冲折返机制等问题提供重要线索。
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| [47] |
Discovery of iron oxide, monazite and barite exsolutions in apatite veins in eclogite from the Chinese Contimental Scientific Drilling(CCSD) project and significance [J].中国大陆科学钻探(CCSD)榴辉岩磷灰石脉体中铁的氧化物、重晶石和独居石出溶物的发现及其意义 [J].
CCSD主孔榴辉岩等UHP岩石中存在团块状到不规则脉体状的磷灰石集合体,它们多与石英脉共生,显微镜下观察发现这些磷灰石脉体存在大量出溶物,电子探针和激光拉曼光谱仪联合测定显示磷灰石主要为氟磷灰石,其中出溶物主要有四类:A．不规则状的磁铁矿和赤铁矿的连生体;B．针状赤铁矿;C．板状到菱型的独居石;D．针状锶重晶石。A类出溶物的延长方向平行于磷灰石的C轴,长度介于10～50μm;B类主要沿磷灰石的C轴方向排列,宽仅为0．5～2μm,多数在1．5μm左右,长度变化较大,为6～50μm;C类独居石出溶体宽约6～10μm,多为6μm,长约50～75μm;D类锶重晶石主要与B类赤铁矿出溶物共生,宽多1．5
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| [48] |
Geochemical characteristics of Zhijin phosphorite type rare-earth deposit, Guizhou Province, China [J].贵州织金磷块岩型稀土矿地球化学特征 [J].
贵州织金磷块岩型稀土矿产于梅树村期戈仲伍组含磷地层,现探明资源量350万吨,其中Y元素占30%以上,为超大型稀土矿床。本文选取4个典型钻孔、一处露头和一采矿坑进行采样,并利用扫描电镜、电子探针、X荧光光谱、和电感耦合等离子体质谱仪对样品的矿石特征和地球化学特征进行了分析。结果表明,稀土元素主要富集于戈仲武组下部的砂屑磷块岩和具层纹构造磷块岩的深色部分,不以独立矿物形式存在,而与磷灰石关系密切。从Fe/Ti、(Fe+Mn)/Ti、Al/(Al+Fe+Mn)比值,As和Sb富集情况,U-Th关系,稀土元素配分模式,δEu异常情况,均反映含矿岩系具有热水沉积成因特征,综合分析认为,戈仲伍组富稀土样品具有热水和风化特征,稀土富集可能与热水沉积或风化改造有关。
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| [49] |
REE minerals at the Songwe Hill carbonatite, Malawi: HREE-enrichment in late-stage apatite [J].
[Display omitted]
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| [50] |
Trace-element signatures of apatites in granitoids from the mtisa inlier, northwestern Queensland [J].
The concentrations of trace elements in apatite from granitoid rocks of the Mt Isa Inlier have been investigated using the laser‐ablation inductively coupled plasma‐mass spectrometry (ICP‐MS) microprobe. The results indicate that the distribution of trace elements (especially rare‐earth elements (REE), Sr, Y, Mn and Th) in apatite strongly reflects the chemical characteristics of the parental rock. The variations in the trace‐element concentrations of apatite are correlated with parameters such as the SiO2 content, oxidation state of iron, total alkalis and the aluminium saturation index (ASI). The relative enrichment of Y, HREE and Mn and the relative depletion of Sr in the apatites studied reflect the degree of fractionation of the host granite. Apatites from strongly oxidised plutons tend to have higher concentrations of LREE relative to MREE. Manganese concentrations are higher in apatite from reduced granitoids because Mn2+substitutes directly for Ca2+. The La/Ce ratio of apatite is well‐correlated with the whole‐rock K2O and Na2O contents, as well as with the oxidation state and ASI. Because apatite trace‐element composition reflects the chemistry of the whole rock, it can be a useful indicator mineral for the recognition of mineralised granite suites, where particular mineralisation styles are associated with granitoids that have specific geochemical fingerprints.
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| [51] |
Gao Li'e, et al. The geochemical nature of apatites in high Sr /Y two-mica granites from the north Himalayan gneiss domes, southern Tibet [J].
藏南北喜马拉雅穹窿高Sr/Y二云母花岗岩中磷灰石地球化学特征及其岩石学意义 [J].URL 摘要
Recent investigations in the Yardoi gneiss dome, the easternmost one of the Northern Himalayan Gneiss Domes (NHGD), have identified two suites of high Sr/Y two-mica granites (TMG) formed at ca. 43~44 Ma and ca.18~20 Ma, respectively. Though they differ substantially in the Sr-Nd isotope systematics and the timing of formation, they show similar characteristics in mineral assemblage as well as in element geochemistry (e.g. high CaO and Sr contents, high Na/K and Sr/Y ratios). LA-ICP-MS analyses were carried out on apatite grains from these TMGs to investigate the geochemical behavior of apatite during their magmatic evolution. Analytical results show that: (1) trace element partitioning behavior between apatite and granitic melt are similar in these TMGs; (2) the Eocene TMG contains relict apatite, possibly inherited from its source; (3) relatively large scattering in trace element compositions among individual apatite grains from the same sample is due to chemical variations in local melts in equilibrium with apatite; (4) fractional crystallization of plagioclase rich in anorthite component had played a primary role in regulating the chemical compositions (e.g. Ca, Na, Sr, and LREE) of melts that crystallized apatite. Our investigation demonstrates that combined investigation of the growth textures and chemical compositions of apatite and plagioclase could yield important insights on the petrogenesis of granitoids.
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| [52] |
Preliminary study on the accessory minerals in granitoids in eastern Jilin and Heilongjiang Provinces [J].
吉黑东部花岗岩类中副矿物锆石、磷灰石、榍石的初步研究 [J].
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| [53] |
Occurrence and genesis of hornblendite-associated nelsonite in northern Hebei Province, China:Evidence from apatite geochemistry [J].冀北与角闪石岩相关铁钛磷灰岩的特征及成因——磷灰石矿物化学的证据 [J].
铁钛磷灰岩在超基性岩中很少发育，笔者野外工作发现冀北铁马哈叭沁超基性岩杂岩体的Fe-Ti-P角闪石岩中发育少量团块状铁钛磷灰岩。本研究选择岩浆演化不同阶段的辉石角闪石岩、角闪石岩和铁钛磷灰岩中的磷灰石进行了电子探针和LA-ICP-MS激光探针分析，对比分析了磷灰石矿物主微量元素特征。不同岩石类型中磷灰石微量元素蛛网图形态十分相似，但铁钛磷灰岩中磷灰石的F、U、Th、Sr、∑REE含量明显更高，连续变化的趋势与岩体岩相序列相符，表明在岩浆演化的晚期阶段，随着分异程度的增强，角闪石岩母岩浆中的Fe-Ti-P组分逐渐富集并达到饱和，从而在角闪石岩中发育团块状的铁钛磷灰岩。磷灰石成因矿物学研究表明铁钛哈叭沁超基性岩杂岩体母岩浆源区中可能存在壳源物质。
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| [54] |
Detrital apatite geochemistry and its application in provenance studies [J]. |
| [55] |
Apatite triple dating and white mica 40Ar/39Ar thermochronology of syntectonic detritus in the central Andes: A multiphase tectonothermal history [J].
ABSTRACT We applied apatite U-Pb, fi ssion track, and (U-Th)/He triple dating and white mica 40 Ar/ 39 Ar thermochronology to syntectonic sedimentary rocks from the central Andean Puna plateau in order to determine the source-area geochronology and source sedimentary basin thermal his- tories, and ultimately the timing of multiple tectonothermal events in the Central Andes. Apa- tite triple dating of samples from the Eocene Geste Formation in the Salar de Pastos Grandes basin shows late Precambrian-Devonian apatite U-Pb crystallization ages, Eocene apatite fi s- sion track (AFT), and Eocene-Miocene (U-Th)/He (ca. 8-47 Ma) cooling ages. Double dating of cobbles from equivalent strata in the Arizaro basin documents early Eocene (46.2 3.9 Ma) and Cretaceous (107.6 7.6, 109.5 7.7 Ma) AFT and Eocene-Oligocene (ca. 55-30 Ma) (U-Th)/He ages. Thermal modeling suggests relatively rapid cooling between ca. 80 and 50 Ma and reheating and subsequent diachronous basin exhumation between ca. 30 Ma and 5 Ma. The 40 Ar/ 39 Ar white mica ages from the same samples in the Salar de Pastos Grandes area are mainly 400-350 Ma, younger than apatite U-Pb ages, suggesting source-terrane cooling and exhumation during the Devonian-early Carboniferous. Together these data reveal multiple phases of mountain building in the Paleozoic and Cenozoic. Basin burial temperatures within the plateau were limited to
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| [56] |
Detrital zircon U-Pb ages provide provenance and chronostratigraphic information from Eocene synorogenic deposits in northwestern Argentina [J]. |
| [57] |
Geochemical research progress of accessory minerals [J].副矿物地球化学研究进展 [J]. |
| [58] |
Apatite (U-Th)/He dating: A review [J]./He定年方法综述 [J]. |
| [59] |
Mesozoic tectonics and dynamic thermal history in Yuanba area of northeastern Sichuan basin: Application of (U-Th)/He dating of apatite and zircon [J].川东北元坝地区中生代构造与动态热演化史——磷灰石、锆石(U-Th)/He定年分析 [J].
通过对川东北元坝地区须家河组(T<sub>3</sub>x)—嘉定组(K<sub>1</sub>j)钻井岩屑样品镜质体反射率和锆石、磷灰石(U-Th)/He定年分析,建立了该区He年龄—深度/温度动态演化模式,推断出元坝地区磷灰石He封闭温度为95℃左右。元坝地区T<sub>3</sub>x-K<sub>1</sub>j中生代地层基本都经历了磷灰石He封闭温度(95℃);所有样品未经历锆石He封闭温度,T<sub>3</sub>x<sup>2</sup>-J<sub>1</sub>z地层部分样品可能经历了约170℃的最高古地温。元坝地区中生代地层在古近纪—新近纪(0.2～36.4 Ma)发生重大冷却抬升剥蚀,剥蚀速率约为109.9m/Ma,K<sub>1</sub>j及以上地层最大抬升剥蚀厚度约为4000m。系统揭示了该区动态热演化历史,中生代地层最高古地温接近于170～190℃,随后地层发生抬升,古地温下降;在36～176 Ma之间时,古地温在95～170℃之间;在0～36Ma时,现今地温小于95℃。
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| [60] |
Apatite (U-Th)/He dating and its application [J].磷灰石(U-Th)/He定年技术及应用简介 [J].
本文阐述了磷灰石 (U_Th) /He定年技术的基本原理和方法、影响因素以及该技术在地质研究中的应用。磷灰石 (U_Th) /He定年是近年来发展起来的一种新型低温热年代学技术 ,能够给出地质体在 4 0～ 85℃低温范围内的独特信息。同裂变径迹定年技术一样 ,磷灰石 (U_Th) /He技术可用于年轻地质体的定年 ,也可确定时代较老的地质体最后一次热事件发生的时间。由于磷灰石 (U_Th) /He年龄数据与样品的海拔或埋藏深度密切相关 ,所以能够很好地约束古地形。结合其他同位素技术如裂变径迹定年技术等还可进行系统的热演化分析 ,如盆地的热史演化。与其他同位素定年技术相比 ,磷灰石 (U_Th) /He定年技术具有测量方便、精度高、所需样品数量少等优点。虽然这种技术目前尚处于不断完善之中 ,但仍不失为研究地质体低温热年代信息的一种有效方法
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| [61] |
Applications of low temperature thermochronology in the tectonogeomorphology evolution of the Tibetan Plateau [J].低温热年代学在青藏高原构造地貌发育过程研究中的应用 [J].
构造地貌学被誉为揭开高原隆升历史的钥匙,但一直受困于年代学的制约。低温热年代学的成熟和进步可为构造地貌研究提供精确的年代学支持。综述了最近几年青藏高原隆起过程研究动态,重点讨论高原构造地貌学的发展问题。建议选取构造地貌发育过程中的直接信息载体(地质地貌岩体)以及相关沉积(新生代盆地沉积物、现代河流沉积物、阶地序列),采用多矿物(磷灰石、锆石等)裂变径迹和(U-Th)/He热年代学这些优势互补方法进行综合研究。通过对这些相互区别又相互联系的信号载体进行系统的年代学分析,据此可重建高原各块体的构造地貌发育过程。提出了几种可能的构造地貌发育模式,并指出低温热年代学信号解译中应当注意的问题。
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| [62] |
Factor impacting the accuracy of apatite(U-Th)/He dating [J].磷灰石(U-Th)/He年龄准确度的影响因素 [J].
磷灰石(U-Th)/He体系因具有已知最低的放射性同位素体系封闭温度(70℃,约3km深度),而被广泛应用于浅地表构造变形及地貌演化研究,是近20a来发展较为迅速的1种热年代学方法.但由于定年原理、测试方法和4He扩散特点等诸多因素的限制,该同位素年龄体系的准确度受到了一定程度的制约.文中归纳了现有文献中常见的10类磷灰石(U-Th)/He定年准确度的影响因素,即粒径、包裹体、α粒子射出效应、α粒子植入效应、U-Th成分环带、辐射损伤、磷灰石化学成分、钐含量、多期热事件和铀系不平衡等,并初步探讨了造成偏差的原因和解决方法,用以抛砖引玉,引起相关研究者的考虑和重视.
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| [63] |
Progress of in situ U-Th/He isotopic dating technique and its application to low temperature deposits [J].原位U-Th/He同位素定年技术研究进展及其低温矿床学应用前景 [J].
应用传统单颗粒方法对目标矿物进行定年具有较高要求（如U、Th等母体同位素均匀分布）,需要耗时的酸溶过程,同时还需进行α粒子射出效应校正。原位U-Th/He同位素定年技术是近年发展起来的一种定年技术,其主要原理是采用激光加热目标矿物,并通过与激光系统连接的稀有气体质谱（Alphachron）和电感耦合等离子体质谱（ICP-MS）分别完成 ~4He和U、Th等母体同位素分析,将 ~4He和U、Th分析结果代入年龄公式计算即可获得目标矿物的U-Th/He年龄。本文阐述了原位U-Th/He同位素定年技术的主要原理、实验测试流程、适用矿物等,重点对原位U-Th/He同位素定年的技术难点和低温矿床学应用前景进行了分析。相对于传统单颗粒方法,原位测试方法解决了两个关键问题：1无需进行α粒子射出效应的校正,提高了定年结果的可靠性和准确度;2能完成母体同位素分布不均匀样品的测试,扩展了U-Th/He同位素定年的应用范围。尽管原位U-Th/He同位素定年技术在侧向加热效应、剥蚀坑体积测定以及标准矿物等方面尚存在一些亟待解决的问题,但已在硅酸盐、磷酸盐、钛铁氧化物等矿物的年代学研究方面展示了良好的应用前景。随着原位U-Th/He同位素定年技术的发展和进步,尤其是硫化物的U-Th/He同位素定年的发展,将为解决低温矿床的年代学问题提供一种新的思路。
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| [64] |
Advances and prospects of apatite fission track thermochronology [J].磷灰石裂变径迹热年代学研究的进展与展望 [J].
综述了磷灰石裂变径迹热年代学研究在退火模型及模拟方法、造山带及造山后剥露历史、构造热成像及地形演变和成矿作用等方面的一些理论和应用成果,分析了目前在磷灰石裂变径迹退火机理、数据解释和应用等方面研究中存在的主要问题,指出了磷灰石裂变径迹热年代学研究今后会朝着深层次退火机理、新的应用领域、自动化技术和可操作性等方向发展.
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| [65] |
Where does sediment come from? Quantifying catchment erosion with detrital apatite (U-Th)/He thermochronometry [J].
We present a new method for tracing sediment using detrital apatite (U-Th)/He (AHe) thermochronometry, and use this to quantify the spatial distribution of catchment erosion in the eastern Sierra Nevada, California. Well-developed age-elevation relationships permit detrital AHe ages to track the elevations where sediment grains were shed from bedrock. We analyzed sediment exiting nonglaciated Inyo Creek and adjacent (formerly) glaciated Lone Pine Creek. Statistical comparison of measured AHe age probability density functions (PDFs) with predicted PDFs based on catchment hypsometries suggests that Inyo Creek is eroding uniformly, consistent with field observations of weathered hillslopes tightly coupled to the fluvial system. In contrast, significant mismatch between measured and predicted PDFs from Lone Pine Creek reveals that sediment derives primarily from the lower half of the catchment. The dearth of older ages is likely due to sediment storage in cirques and moraines and/or focused erosion at intermediate elevations, both potential consequences of glacial modification. Measured PDFs can also improve cosmogenic nuclide-based erosion rates by more accurately scaling nuclide production rates. Our results demonstrate the utility of detrital AHe thermochronometry for quantifying erosion in fluvially and glacially sculpted catchments.
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| [66] |
Apatite low-temperature thermochronometry and applications to Tarim Basin in the northwestern China [J].磷灰石低温热年代学技术及在塔里木盆地演化研究中的应用 [J].
随着磷灰石低温热年代学技术理论研究的不断完善和发展,它已被广泛用于地质体定年、构造-热演化、地形地貌演化等研究领域。该文首先对磷灰石裂变径迹和（U-Th）/He热定年技术近几年的研究进展进行了综述,在此基础上阐述了低温热年代学方法在塔里木盆地构造-热历史和物源分析领域的应用效果。多组分动力学退火模型的建立、激光剥蚀ICP-MS方法的提出及裂变径迹自动测试仪的开发极大地推动了磷灰石裂变径迹技术的发展。对于磷灰石（U-Th）/He热定年技术,FT-等效圆校正模型极大地降低了He年龄校正过程中产生的误差;辐射损伤捕获扩散模型首次揭示了晶格缺陷对4 He扩散的影响模式;辐射损伤积累和退火模型有效地解释了克拉通盆地部分磷灰石样品裂变径迹年龄小于He年龄的现象。塔里木盆地巴楚隆起的低温热年代学数据和热史模拟结果揭示出巴楚隆起自中生代以来曾经历过185-140Ma、140-100Ma、75-50 Ma等三期快速隆升事件,主要是由羌塘地体、拉萨地体、印度板块与欧亚板块南缘碰撞引起的。塔北隆起钻孔内浅部样品的磷灰石裂变径迹年龄和（U-Th）/He年龄都大于相应的地层年龄,记录的是物源区南天山的热信息;其热史模拟结果揭示出南天山曾经历过晚中新世—早上新世（15-5 Ma）一期快速隆升事件,并以此构建了塔里木盆地北部与南天山晚中新世—上新世构造-沉积耦合演化模式。
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| [67] |
In-situ determination of major and trace elements in calcite and apatite, and U-Pb ages of apatite from the Oka carbonatite complex: Insights into a complex crystallization history [J]. |
| [68] |
Lead diffusion in apatite and zircon using ion implantation and ruther ford backscattering techniques [J].
Diffusion coefficients for Pb in zircon determined in this study are greater than those obtained from a single experimental measurement and estimates of Pb diffusion based on geochronologic data and U/ Pb zoning in natural zircons. The differing results for zircon and apatite obtained in this study appear to be related to each mineral's ability to anneal the radiation damage induced by ion implantation.
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| [69] |
In situ U-Pb dating of apatite using LA-MC-ICP-MS [J].磷灰石微区原位LA-MC-ICP-MS U-Pb同位素定年 [J].
利用激光剥蚀多接收器电感耦合等离子体质谱法（LA-MC-ICP-MS），建立了磷灰石微 区原位U-Pb同位素定年新方法，本文给出了这一新方法的分析流程，报道了利用这一新方法对5个磷灰石样品的分析结果，并应用同位素稀释-热电离质谱法 （ID-TIMS）对一些样品定年结果进行了验证。磷灰石工作标样SDG的U-Pb同位素年龄： （1596±15）Ma（MSWD=1．5，n=7，LA-MC-ICP-MS），（1602±13）Ma（MSWD=0．578，n=5，ID- TIMS）；某铁矿石中磷灰石的LA-MC-1CP-MSU-Pb同位素年龄：（125±14）Ma（MSWD=0．68，n=25）， （124．2±3．5）Ma（MSWD=1．5，n=37）；新疆阿尔金地区片麻岩中磷灰石的LA-MC-ICP-MSU-Pb同位素年龄： （250．8±3．9）Ma（MSWD=8．6，n=26），（245．4±2．9）Ma（MSWD=2．1，n=39）。
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| [70] |
Evidence of a full west Antarctic ice sheet back to the early Oligocene: Insight from double dating of detrital apatites in Ross Sea sediments [J].
Abstract The West Antarctic Ice Sheet is the most unstable component of the Antarctic cryosphere. Its fluctuations are well documented since the Pliocene, but its behaviour over the last 3502Ma is more controversial, particularly during periods of past high global p CO2 values similar to those predicted in future global climate scenarios. Here, we present new U–Pb dating of detrital apatite grains (previously dated by the fission-track method) from Cape Roberts Project Oligocene to Pliocene marine sediments in the Ross Sea. Two past ice-flow patterns were identified: one formed by outlet glaciers sourcing short-travelled apatites and one, northerly directed, bringing far-travelled apatite grains. The latter provides the first robust physical evidence for the presence and repeated expansion of an Oligocene West Antarctic Ice Sheet.
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| [71] |
New constraints on the provenance of the ANDRILL AND-2A succession (Western Ross Sea, Antarctica) from apatite triple dating [J].
[1] Apatite triple dating (fission track, U-Pb and U-Th/He techniques) has been applied to detrital grains from the sedimentary core drilled during the ANDRILL 2A project, which documents the Miocene history of the Victoria Land Basin (western Ross Sea). High-temperature cooling ages show two main clusters (about 30 and 500 Ma) whereas most of low-temperature data are late Oligocene-Early Miocene in age. These latter data are related to the exhumation of the Transantarctic Mountains south of the Discovery Accommodation Zone. Comparison between low-temperature ages suggests that the Transantarctic Mountains have been in a phase of post-orogenic decay since at least 30 Ma. The Oligocene U-Pb data demonstrate the presence of a volcanic event well before the McMurdo volcanic group, whose onset is commonly places at 19 Ma. The location of the volcanic centers is unknown, but they could be below the Ross Ice Shelf south of drilling site. As a whole, these data indicate a major flow of sediments from south to north with only minor contributions from nearby outlet glaciers of the East Antarctic Ice Sheet.
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| [72] |
Sr-rich apatite from the Dangzishan leucitite-ijolite xenoliths (Heilongjiang Province): Mineralogy and mantle-fluid metasomatism [J].荡子山白榴霓霞岩包体中富Sr磷灰石的发现及其成因矿物学研究 [J].
荡子山白榴霓霞岩包体中含有大量的富锶磷灰石.利用电子探针微束分析技术对富锶磷灰石的赋存 状态、晶形、矿物共生、成分变化以及成因机制进行了深入细致的研究,发现富锶磷灰石有短柱状和细长柱状两种晶形,并多被其他矿物包裹,表明它们形成于岩浆 结晶的早期阶段,其成分为氟磷灰石.之后被富锶流体沿着氟磷灰石颗粒的边缘进行交代,从而形成了富锶磷灰石,交代方式为类质同像置换.富锶磷灰石中SrO 含量的变化反映出体系中碱度的变化,体系中的碱度升高时,磷灰石矿物中Sr置换Ca的数量增加,而当体系中的碱度降低时,已经进入到磷灰石矿物晶格中的 Na,LREE和Sr离子也会从中分离出来而导致这些阳离子数降低.因此,Sr置换Ca的数量对体系中的碱度变化趋势有着明显的指示意义.根据电子探针成 分分析数据计算得出阳离子的个数,富锶磷灰石结构式可写为 （Ca3.15～4.963Sr0.019～1.510Ba0.00～0.030Na0.006～0.108REE0.106～0.153） （P2.842～3.028Si0.009～0.094）O12（F0.675～1.079,Cl0.000～0.256,OH– 0.084～0.297）.利用配有193nm激光的Neptune多接收等离子体质谱仪（LA-MC-ICPMS）,对富锶磷灰石原位微区Sr,Nd同 位素进行了分析.将分析结果与白榴霓霞岩包体及包体的寄主岩Sr,Nd同位素组成进行了比较,发现交代早期岩浆结晶成因氟磷灰石的富锶流体与白榴霓霞岩包 体及包体的寄主岩来自不同的源区,其中,前者来自较亏损地幔,而后两者则来自较富集地幔.
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| [73] |
Spatial variations of trace element and Sr isotopic compositions of apatite in eclogite from the CCSD main hole [J].CCSD主孔榴辉岩中磷灰石微区微量元素和Sr同位素组成研究 [J].
本文利用LA-ICP-MS和LA-MC-ICP-MS对CCSD-MH中一件强退变多硅白云母榴辉岩中一粗粒(～2mm×6.5mm)磷灰石进行了详细的微区微量元素和Sr同位素组成研究.线扫描剖面分析和单点分析结果共同表明该磷灰石颗粒的微量元素和Sr同位素组成不均一.总体上Na、Sr、LREE、MREE、U、Th和Pb等元素具有从中心到两侧含量逐渐降低的特征.磷灰石主体部分HREE含量均一,但和石榴石紧密相邻的边部(～400μm)HREE显著富集.Na、Sr、LREE和MREE等元素在个别区域明显具有先升高、然后再降低的变化规律.磷灰石最边部(＜200μm)相对于核部区域显著高87Sr/86Sr比值.结合磷灰石中微量元素分配和扩散行为的实验研究以及磷灰石晶体化学特征,磷灰石微量元素组成变化应主要记录了磷灰石复杂的生长过程.Sr、LREE和MREE从核部到边部逐渐降低的总体特征指示磷灰石从中心向两侧的生长过程,而局部出现的次级先升高-再降低的变化规律则反映了磷灰石经历的多次溶解和再生长作用.HREE含量均一的磷灰石主体形成于石榴石稳定存在的超高压变质作用阶段.和石榴石紧密相邻的磷灰石边部显著富集HREE的特征则是折返过程中短时增温作用导致石榴石释放HREE和/或退变质阶段石榴石分解释放HREE共同作用的结果.磷灰石最边部显著高87Sr/86Sr的特征则记录了角闪岩相退变质阶段多硅白云母的分解作用.
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| [74] |
In situ Sr-Nd isotopic measurement of apatite using lase ablation multi-collector inductively coupled plasma-mass spectrometry [J].磷灰石Sr-Nd同位素的激光剥蚀—多接收器电感耦合等离子体质谱微区分析 [J].
磷灰石是常见的副矿物,具有较高的Sr-Nd含量和较低的Rb含量,对其微区Sr-Nd同位素组成的准确测定可以为精细地质作用过程的探讨提供重要的地球化学信息。激光剥蚀-多接收器电感耦合等离子体质谱（LA-MC-ICPMS）具有分析速度快、分析精度高和空间分辨率高的特点,特别适合大量细颗粒磷灰石样品的Sr-Nd同位素分析,而同位素干扰的精确扣除和仪器质量歧视校正是原位微区分析准确获得Sr-Nd同位素比值的关键。本文利用 LA-MC-ICPMS技术,综合最新发表的Kr、Rb、稀土二价离子及钙聚合物对Sr同位素的干扰扣除方法和Sm对Nd同位素的干扰扣除方法,对仪器的质量歧视进行了校正,建立了磷灰石原位Sr-Nd同位素分析方法。用此方法对一个磷灰石国际标准样品Durango和两个实验室标准Apatite 1 和 PE进行了详细的Sr-Nd同位素测定,结果表明,对Sr-Nd含量足够高的磷灰石样品可以准确地获得其Sr-Nd同位素组成,测试结果与文献报道值或热电离质谱（TIMS）测试值在误差范围内一致,Sr同位素的测试精度〈0.015%（2SD）,Nd同位素的测试精度〈0.005%（2SD）,达到了国际同类实验室水平;且三个磷灰石标准样品同位素组成较为均一,都是理想的原位Sr-Nd同位素分析参考物质。
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New method and new technique for the high precision chronolgy of Lu-Hf isotopic [J].高精度Lu-Hf同位素测定的新技术与新方法 [J].
综述了Ｌｕ－Ｈｆ同位素体系的基本地质地球化学特征，对比了Ｌｕ－Ｈｆ同位素现有的分析方法，并介绍了包括化学流程在内的应用多接收器双耦合等离子体质谱仪（ＭＣ－ＩＣＰ－ＭＳ）进行高精度和高准确度，Ｌｕ－Ｈｆ同位素分析的原理和测试过程，列举了部分最新地质应用成果。
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| [76] |
Rare earth element diffusion in apatite [J].
Diffusion of rare earth elements (REEs) in natural and synthetic fluorapatite has been characterized under anhydrous conditions. Three types of experiments were run. In the first set of experiments, Sm was introduced into the apatite by means of ion implantation, with diffusivities extracted through measurement of the “relaxation” of the implanted profile after diffusion anneals. The second group consisted of “in diffusion” experiments, in which apatite was immersed in reservoirs of synthetic REE apatite analogs of various compositions. The final set of experiments was “out-diffusion” experiments run on synthetic Nd-doped apatite immersed in a reservoir of synthetic (undoped) fluorapatite. REE depth profiles in all cases were measured with Rutherford Backscattering Spectrometry. Diffusion rates for the REE vary significantly among these sets of experiments. For the ion-implantation experiments, the following Arrhenius relation was obtained for Sm, over the temperature range 750°C to 1100°C: D imp =6.3×10 617 exp(61298±17 kJ/mol/RT) m 2 /s Diffusion of a series of REE, from light to heavy, was investigated in the “in-diffusion” experiments. Over the temperature range 800°C to 1250°C, the following Arrhenius relations are obtained for La, Nd, Dy, and Yb, for in-diffusion experiments using REE silicate oxyapatite sources: D La =2.6×10 617 exp(61324±9 kJ/mol/RT) m 2 /s D Nd =2.4×10 616 exp(61348±13 kJ/mol/RT) m 2 /s D Dy =9.7×10 617 exp(61340±11 kJ/mol/RT) m 2 /s D Yb =1.3×10 618 exp(61292±23 kJ/mol/RT) m 2 /s Diffusivities of the REE in these “in-diffusion” experiments are all quite similar, suggesting little difference in diffusion rates in apatite with increasing ionic radii of the REEs. The “out-diffusion” experiments on the Nd-doped synthetic apatite, over the temperature range 950°C to 1400°C, yield the Arrhenius law: D out =9.3×10 616 exp(61392±31 kJ/mol/RT) m 2 /s The differences in REE diffusion among these three sets of experiments (i.e., ion implantation, in-diffusion, and out-diffusion) may be attributable to the differences in substitutional processes facilitating REE exchange. The fastest diffusion, found in the ion-implantation experiments, is likely largely governed by simple light REE +3 62 REE +3 exchange, with no charge compensating species necessary. REE transport in the in-diffusion experiments requires movement of an additional charge-compensating species, either through the substitutions REE +3 + Si +4 62 Ca +2 + P +5 or REE +3 + Na +1 62 2 Ca +2, and thus proceeds more slowly than simple REE exchange. Slowest of all is Nd out-diffusion from the synthetic Nd-doped apatite, for which neither charge compensating species are present nor REEs available in the surrounding reservoir to facilitate Nd exchange. This observed dependence of REE diffusion rates on the exchange process involved has important geochemical implications. These findings indicate that REE isotope and chemical signatures can become decoupled in apatite, with light REE isotope exchange proceeding much more rapidly than REE chemical diffusion altering total REE concentrations. Under temperatures typical of thermal events, REE zoning (involving differences in REE concentration across zones) of a given dimension might persist over time periods two orders of magnitude greater than those under which zoning of REE isotopes (without significant changes in total REE) on similar scale is preserved.
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| [77] |
Lu-Hf and Pb SL geochronology of apatites from Proterozoic terranes: A first look at Lu-Hf isotopic closure in metamorphic apatite [J].
The mineral apatite is characterized by elevated and highly variable Lu/Hf ratios that, in some cases, allow for single-crystal dating by the Lu-Hf isotopic system. Apatites from the Adirondack Lowlands and Otter Lake area in the Grenville Province, and from the Black Hills, South Dakota, yield Lu-Hf ages that are consistently older than their respective Pb step leaching ages. Isotopic closure for the Lu-Hf system, therefore, occurs before U-Pb system closure in this mineral. In the Adirondack Lowlands, where H 2O activity was low, Lu-Hf systematics of cm-sized apatite crystals remained undisturbed during upper amphibolite facies metamorphism (65700 to 675 °C) at 1170–1130 Ma. The relatively old Lu-Hf ages of 1270 and 1230 Ma observed for these apatites correlate with decreasing crystal size. In contrast, apatite from the fluid-rich Otter Lake area and Black Hills yields unrealistically low apparent Lu-Hf closure temperatures, implying that in these apatites, fluids facilitated late exchange. The Lu-Hf ages for the metamorphic apatites were thus controlled either by the prevailing temperature and grain size, or by fluid activity.
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Lu-Hf Apatite Geochronology of mafi cumulates: An example from a Fe-Ti mineralization at Smålands Taberg, southern Sweden [J]. |
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U-Pb and Hf isotopic data of detrital zircons from the Laohutang formation in the Wugongshan area, central Jiangxi Province: Constraint on sedimentary age and material source [J].江西武功山地区老虎塘组碎屑锆石U-Pb年龄和Hf同位素:沉积时代厘定及其源区特征 [J]. |
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U-Pb age and Lu-Hf isotope of detrital zircons from the meta-sedimentary rocks in the Yunkai region and their geological significance [J].云开地区变质沉积岩碎屑锆石U-Pb年龄、Lu-Hf同位素特征及其地质意义 [J].
华夏陆块西南部云开地块变质杂岩主要由天堂山岩群和云开群以及古生代花岗质岩石组成。天堂山岩群主要由片麻岩、变粒岩、石英岩等岩石组成,变质程度较深;云开群主要由片岩、板岩、千枚岩、变质砂岩等岩石组成。应用LA-ICP-MS U-Pb微区定年和Lu-Hf同位素分析以及全岩地球化学分析方法,本文对天堂山岩群和云开群变质沉积岩进行了研究。在阴极发光图像中,变质沉积岩的锆石显示岩浆震荡环带,但普遍遭受重结晶改造及存在变质增生边。由于变质增生边普遍较窄,U-Pb定年和Hf同位素分析几乎都在具岩浆环带和重结晶结构的成分域上完成的。具岩浆环带和重结晶结构的成分域的Th/U比值普遍大于0.1。年龄变化从3000~500Ma,但主要集中在600~1200Ma之间,主峰值为960Ma左右。碎屑锆石的ε_(Hf)(t)值在-25.6~15.4之间,两阶段Hf模式年龄在972~4496Ma之间。全岩地球化学分析显示LREE富集,HREE亏损,具有较明显的负Eu异常(δEu=0.55~0.71),天堂山岩群与云开群REE配分模式一致,反映源区物质相似,主要来源于花岗质地壳物质。结合前人研究成果,可得出如下结论:天堂山岩群与云开群形成时代没有明显差别,虽然它们在变质变形方面存在较明显区别;天堂山岩群和云开群沉积时代为古生代早期-新元古代;格林威尔期岩浆岩为主要物源区,新元古代时期华夏陆块处于格林威尔造山带内与之相邻;华夏陆块存在太古宙古老陆壳。
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| [81] |
Sm-Nd isotopic dating of apatite separates from Heiyingshan high-grade iron deposit, Inner Mongolia [J].内蒙古黑鹰山富铁矿床磷灰石钐-钕同位素年龄及其地质意义 [J]. |
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Sulphur and carbon isotopes of sedimentary apatite, Guizhou Province and their geological significance [J].黔中沉积磷灰石的硫碳同位素及其地质意义 [J].
本文研究了黔中磷块岩中磷灰石的结构硫同位素组成。磷灰石的δ３４Ｓ值为３４．２‰～４２．４‰，它高于同期海水的δ３４Ｓ（约３４．２‰），也高于共生的成岩黄铁矿的δ３４Ｓ（１５．４‰～１９．８‰），表明磷灰石形成于富有机质沉积物早期成岩作用硫酸盐还原带的最上部，其间同时伴有大量硫酸盐细菌的还原过程。磷灰石的碳同位素组成（δ１３Ｃ＝－３．６３‰～１．０‰），表明它含有微生物有机质分解演化而来的ＣＯ２－３，而磷灰石比胶结白云石更富集轻同位素则反映出沉积阶段生物作用的影响比成岩阶段更为明显
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| [83] |
Isotopic geochemistry of apatite from carbonatite in central Shandong [J].鲁中碳酸岩中磷灰石同位素地球化学研究 [J].
鲁中地区分布着１００多个碳酸岩体，微量元素含量及稀土配分等均与世界典型碳酸岩相近。而碳酸岩的碳氧及斑晶磷灰石的锶、钕同位素组成与典型地幔物质有差异，与富集地幔颇为近似，从而证实在山东地区陆壳下存在富集地幔源区。
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