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地球科学进展, 2019, 34(4): 382-398 doi: 10.11867/j.issn.1001-8166.2019.04.0382

固体地球科学

金川超大型Ni-Cu-(PGE)矿床橄榄石微量元素特征及地质意义

康健,1,2, 陈列锰,1, 宋谢炎1, 戴智慧1, 郑文勤1

1. 中国科学院地球化学研究所 矿床地球化学国家重点实验室,贵州 贵阳 550081

2. 中国科学院大学,北京 100049

Trace Elements in Olivines from the Giant Jinchuan Ni-Cu-(PGE) Deposit, NW China, and Its Geological Implication

Kang Jian,1,2, Chen Liemeng,1, Song Xieyan1, Dai Zhihui1, Zheng Wenqin1

1. State Key Laboratory of Ore Deposit Geochemistry, Institude of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China

2. University of Chinese Academy of Sciences, Beijing 100049, China

通讯作者: 陈列锰(1981-),男,湖南耒阳人,研究员,主要从事岩浆矿床成因研究. E-mail:chenliemeng@vip.gyig.ac.cn

收稿日期: 2018-12-25   修回日期: 2019-02-03   网络出版日期: 2019-05-22

基金资助: 国家重点研发计划项目“典型成矿系统演化规律与时空自相似结构”.  编号:2016YFC0600503
国家自然科学基金面上项目“Mg-Fe同位素对东昆仑造山带夏日哈木和石头坑德含铜镍硫化物岩体源区的制约”.  编号:41873026

Corresponding authors: Chen Liemeng(1981-), male, Leiyang City, Hu'nan Province, Professor. Research areas include magmatic deposit genesis. E-mail:chenliemeng@vip.gyig.ac.cn

Received: 2018-12-25   Revised: 2019-02-03   Online: 2019-05-22

作者简介 About authors

康健(1994-),男,甘肃天水人,硕士研究生,主要从事岩浆硫化物矿床研究.E-mail:kaingjian@mail.gyig.ac.cn , E-mail:kaingjian@mail.gyig.ac.cn

摘要

我国金川超大型铜镍硫化物矿床是世界上第三大在采岩浆硫化物矿床,Ni开采量仅次于俄罗斯Noril’sk-Talnakh和加拿大Sudbury矿床,其成因研究备受关注。利用激光—等离子体质谱(LA-ICP-MS)原位分析了金川岩体中橄榄石微量元素含量,并探讨了影响元素含量变化的因素,进而阐述成岩及成矿过程。分析结果显示橄榄石中元素Ni,Cr与Fo呈负相关,Mn/Fe与Fo呈正相关,而Mn/Zn,Zn/Fe与Fo无相关性。在原始地幔橄榄石多元素标准化图中,金川Ⅰ号和Ⅱ号岩体橄榄石具相同的配分模式,均显示Cr,V,Ni,Co和Ti的亏损,富集不相容元素Zr,Y,Ti,Sc和Ca的特征。元素变化特征暗示Ⅰ号和Ⅱ号岩体具相同的母岩浆成分;与铬尖晶石的共结使橄榄石亏损Cr,V和Ti元素,而熔离的硫化物及其与橄榄石的相互反应共同影响着橄榄石中Ni和Co元素的含量。Ⅱ号岩体橄榄石较Ⅰ号岩体具较低的Cr和V含量,暗示Ⅱ号岩体母岩浆较Ⅰ号岩体经历了更高程度的演化。橄榄石高的Mn/Zn值(>13)和低的Zn/Fe值(<11)指示金川岩体岩浆可能起源于橄榄岩地幔的部分熔融,而非辉石岩地幔源区。

关键词: 橄榄石 ; 微量元素 ; 岩浆演化 ; 金川岩体

Abstract

The giant Jinchuan magmatic sulfide deposit in China is the third largest mining deposits in the world. Although many research have been done, there still exist some debates in the genesis of deposit. This study using the LA-IC-MS to obtain the trace elements concentrations of the olivine in order to discuss the mechanism of influence the element variability and illustrate the process of magmatism and ore-forming. The analytical results show that Ni, Co correlate negatively with Fo in the olivine, Mn/Fe is positively correlate with Fo, while Mn/Zn and Zn/Fe show no obvious correlation with Fo. The primitive mantle olivine-normalized trace element patterns of the Jinchuan olivine show that Jinchuan Ⅰ, Ⅱ intrusions have the same trace elements characteristics, which display negative Cr, V, Ni, Co and Ti anomalies and enrichment of Zr, Y, Ti, Sc and Ca. The multi-element patterns of the Jinchuan olivine imply same parental magma in the intrusion Ⅰ and Ⅱ. The spinel which cocrystallization with the olivine make it display negative Cr, V and Ti anomalies. The contents of Ni and Co in olivine are influenced by the process of sulfide segregation and the reaction between sulfide and olivine. The lower content of Cr and V in olivine of the intrusion Ⅱ compared with the intrusion Ⅰ imply that the parental magma of the intrusion Ⅱ was more evolved. Higher Mn/Zn (>13) ratios and lower Zn/Fe (<11) ratios indicate that the magma of Jinchuan intrusion likely originate from partial melting of peridotite mantle possibly, instead of pyroxene mantle sources.

Keywords: Olivine ; Trace elements ; Magmatic evolution ; Jinchuan instrusion.

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本文引用格式

康健, 陈列锰, 宋谢炎, 戴智慧, 郑文勤. 金川超大型Ni-Cu-(PGE)矿床橄榄石微量元素特征及地质意义. 地球科学进展[J], 2019, 34(4): 382-398 doi:10.11867/j.issn.1001-8166.2019.04.0382

Kang Jian. Trace Elements in Olivines from the Giant Jinchuan Ni-Cu-(PGE) Deposit, NW China, and Its Geological Implication. Advances in Earth Science[J], 2019, 34(4): 382-398 doi:10.11867/j.issn.1001-8166.2019.04.0382

1 引 言

金川超镁铁质岩体位于我国甘肃省西北部,是赋存有仅次于俄罗斯Noril’sk-Talnakh和加拿大Sudbury矿床的世界第三大在采岩浆铜镍矿床[1,2,3]。因此,其成岩及成矿过程备受中外地质学家的关注[4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]。该岩体呈透镜状产出,地表出露面积仅1.34 km2,却含有至少550×104 t金属镍和350×104 t铜。金川岩体二辉橄榄岩中锆石/斜锆石的热表面电离同位素稀释质谱(Isotope Dilution-Thermal Ionization Mass Spectrometry,ID-TIMS)年龄约为831 Ma[11],岩体形成可能与Rodinia超大陆的裂解密切相关[19,20]。汤中立[4,7]较早认为金川矿床是“幔源岩浆深部熔离,依次贯入”的结果,提出了经典的“小岩体成大矿”的成矿模式。相反,Chai等[6]认为金川岩体是大型侵入体的根部,是岩浆原地分异和硫化物熔离的产物。近年来,矿物学、元素地球化学和Sr-Nd同位素研究表明金川岩体母岩浆为高MgO的玄武质岩浆,起源于富集岩石圈地幔的部分熔融[5,13,21,22],且上升过程中经历了较高程度的地壳同化混染作用[9,14,19,23,24]。橄榄石成分研究认为金川岩体存在深、浅2个岩浆房,母岩浆进入浅部岩浆房之前发生了少量橄榄石的早期结晶[25,26]。橄榄石粒径统计表明金川Ⅰ号岩体橄榄石是早期结晶的橄榄石在浅部岩浆房中再生长形成的,而Ⅱ号岩体橄榄石以浅部岩浆房中原地结晶生长为主[18]。Song等[12]通过岩相学、地球化学以及构造恢复认为F16-1断层两侧原本为2个相互独立的岩体,同时认为西岩体是镁铁质岩浆携带硫化物乳珠因重力沉降—聚集而成矿,而东岩体是深部分异的硅酸盐熔体“晶粥”和含硫化物的橄榄石熔体“晶粥”依次挤入形成的,硫化物中低的PGE品位暗示经历了硫化物的二次熔离作用[12,13]

橄榄石是基性—超基性岩体中最主要的硅酸盐矿物,而且是基性岩浆早期结晶的矿物;因此,其成分可以反演许多母岩浆的信息。特别是在岩浆硫化物矿床成因研究中,橄榄石的成分(Mg,Fe和Ni)通常可以用来指示母岩浆性质(Fo值)和硫化物熔离的程度(Ni亏损)[27,28,29,30]。近年来,随着激光—等离子体质谱(Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer)原位微区技术的成熟发展,橄榄石微量元素地球化学已经成功应用到地幔岩石学和玄武岩的成因研究方面[31,32,33,34,35,36]。例如,橄榄石斑晶中Li,Ni,Sc,Al和Mn等元素组合可以识别岩浆源区的富集交代作用;橄榄石中Sc,Zr,Al和Mn等元素组合可以识别地幔橄榄岩源区的矿物组合。然而,目前对含矿堆晶岩中橄榄石微量元素地球化学特征的研究还很薄弱,利用橄榄石微量元素来示踪岩浆硫化物矿床形成的关键过程(如岩浆混合、熔体分异、同化混染[37]和硫化物饱和)有待深入研究。此外,由于金川岩体地表没有找到相应的玄武岩,导致岩石圈地幔富集的机理及其与地幔柱的成因联系仍然不清楚。近年来,橄榄石微量元素如Mn,Ni和Zn等[33,34,38]可以有效示踪岩浆源区,因此利用橄榄石地球化学可能为上述问题提供依据。本研究以金川超大型Ni-Cu-(PGE)矿床为例,利用激光—等离子体质谱(LA-ICP-MS)原位分析技术研究控制橄榄石微量元素成分变化的因素,并试图进一步制约金川矿床的岩浆起源、演化和矿石形成的过程。

2 金川岩体地质特征及采样

金川超镁铁质岩体位于华北克拉通西南缘阿拉善板块龙首山隆起带中(图1a)。龙首山北缘与潮水盆地相邻,南缘与祁连褶皱带相隔。在北西—南东走向龙首山地体中,新元古代和古生代砾岩、砂岩及灰岩不整合覆盖于古元古代和中元古代变质单元上。一系列北西—南东走向的镁铁质—超镁铁质岩侵入到中—古元古代变质岩中,包括金川、毛草泉、青石窑、青井子和藏布台等岩体(图1b)。大多数岩体都发育有弱的硫化物矿化作用,但到目前为止,仅发现金川岩体赋存具经济价值的铜镍硫化物矿石[39]

图1

图1   龙首山地体和金川岩体地质简图

Fig.1   Geological maps of the Longshou Terrain and the Jinchuan intrusion

(a)中国大地构造单元图,金川岩体位于华北克拉通的西南缘(据参考文献 [26] 修改);(b)龙首山地体简要地质图(据参考文献[20]修改);(c)金川岩体地质图和剖面图,简要显示了岩相和矿体的分布(据参考文献[13,17]修改)

(a)The main tectonic units of China, and the location of the Jinchuan intrusion at the southwestern margin of the North China Craton(modified after reference [26]);(b)Geological sketch map of Longshou terrain(modified after reference [20]); (c)Simplified geological map and a cross section of the Jinchuan intrusion, showing the distribution of rocks and the largest ore bodies(modified after references [13,17])


金川含铜镍硫化物超基性岩体长约6 500 m,宽20~500 m,出露面积仅1.34 km2,最大延深超过 1 100 m,其直接围岩为片麻岩、大理岩和混合岩。金川含矿岩体被一系列北东东向左行平移断层(F8,F16-1和F23)分成4个部分,由西至东编号依次为III,I,II和IV,各个部分的规模、形态以及含矿特征各不相同(图1c)[39]。Song等[12]基于岩相学、地球化学以及构造恢复认为金川原本为东、西2个岩体,F16-1以西的I和III部分构成西岩体,赋存24号矿体;F16-1以东的II和IV部分构成东岩体,赋存1号和2号矿体。

金川Ⅰ号和Ⅱ号岩体均主要由橄榄岩、二辉橄榄岩、橄榄辉石岩组成,岩体边缘分布有少量斜长石二辉橄榄岩和辉石岩。其中,金川Ⅰ号岩体由上、下2个不同结构和截然接触的岩相单元组成[13,39]。上部岩相带中橄榄石呈细粒状(0.5~3 mm)构成主要的堆晶相(图2a),辉石和长石则充填于堆晶橄榄石的间隙中(图2b,2c);该岩相带从下到上橄榄石含量逐渐减少,辉石含量依次增多,体现为由纯橄岩过渡到二辉橄榄岩再到少量辉石岩。矿化呈稀疏浸染状分布于底部纯橄岩相中。下部岩相带中橄榄石呈粗粒状(4~7 mm),岩相旋回与上部单元类似;但底部粗粒纯橄岩中矿化呈网脉状,浸染状矿化分布于其上二辉橄榄岩中。金川Ⅱ号岩体则具呈中心对称分布的岩相学特征[39,40],由中间中—细粒的纯橄岩向两侧边缘粗粒的二辉橄榄岩、少量斜长石二辉橄榄岩和辉石岩过渡,体现为从岩体中心到边缘橄榄石含量逐渐减少,辉石含量依次增多的特点。

图2

图2   金川岩体不同岩相中橄榄石及硫化物结构

Fig.2   Olivine and sulfide textures of the Jinchuan intrusion in different petrofacies

(a)纯橄榄岩发育堆晶结构(单偏光);(b)二辉橄榄岩中发育包橄结构,被单斜辉石包裹的橄榄石较新鲜(正交偏光);(c)斜长石二辉橄榄岩中橄榄石构成主要堆晶相,辉石和斜长石构成粒间相(正交偏光);(d)橄榄石中包裹有铬尖晶石(反射光);(e)浸染状矿化中硫化物呈彼此不连续状分布(反射光);(f)网脉状矿化中堆晶橄榄石颗粒被硫化物包裹(反射光); Ol:橄榄石;Cpx:单斜辉石;Opx:斜方辉石;Pl:斜长石;Sp:铬尖晶石;Sul:硫化物

(a)The cumulate textures of Dunite (plane-polarized light);(b)Olivine grains enclosed by clinopyroxene are more fresher in inlherzolite and named poikilitic texture (cross-polarized light);(c)Olivine is the main cumulus phase in plagioclase lherzolite which plagioclase and clinopyroxene are interstitial to cumulus olivine (cross-polarized light);(d)Cr-spinel inclusion in olivine (reflected light);(e)Disseminated sulphides are discontinuous with each other among the olivine grains (reflected light);(f)Olivine included in net-textured sulphide (reflected light); Ol: Olivine; Cpx: Clinopyroxene; Opx: Orthopyroxene; Pl: Plagioclase; Sp: Spinel; Sul: Sulfide


金川铜镍硫化物矿化以网脉状和浸染状为主(图2e,2f),矿石矿物主要为磁黄铁矿、镍黄铁矿和黄铜矿。岩体蚀变以蛇纹石化最为普遍(图2),其次是透闪石化、阳起石化、绿泥石化和滑石—碳酸盐化等,在不同矿体的结合部位,构造活动较强,岩石几乎全部蚀变[39]

本次研究样品采自金川I号和II号岩体各个岩相带中(表1)。其中,I号岩体上部岩相带及部分下部岩相带的样品采自龙首矿(24号矿体)露天矿坑,少量下部岩相带样品采自24号矿体井下采场;II号岩体样品均采自24行勘探线地表露头(图1)。

表1   金川岩体橄榄石主、微量元素分析结果

Table 1  The major and trace elements of olivine in Jinchuan intrusion

采样位置I号岩体下部岩相带
样号JC06-233JC13-106JC13-102JC13-101JC13-107JC13-230
岩性粗粒硫化物橄榄岩粗粒二辉橄榄岩粗粒硫化物二辉橄榄岩粗粒斜长二辉橄榄岩粗粒二辉橄榄岩粗粒二辉橄榄岩
点号Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-4Ol-1Ol-2Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2
主量元素质量百分含量/%MgO43.443.343.642.142.942.343.741.542.142.742.042.941.641.642.341.941.0
Al2O30.00.00.00.10.00.00.10.00.10.10.00.00.00.00.00.00.0
SiO240.241.040.540.040.340.040.139.739.339.139.840.239.739.539.639.139.5
CaO0.10.10.10.50.10.00.10.10.20.00.10.00.10.20.10.00.0
TiO20.00.00.10.00.00.10.00.10.10.00.00.00.00.00.10.00.0
Cr2O30.00.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
MnO0.20.20.20.20.20.20.20.30.20.20.20.20.20.20.20.20.2
FeO15.014.915.015.115.816.015.817.417.217.217.216.517.616.816.617.917.1
Na2O0.00.00.00.10.10.00.00.00.00.00.00.00.00.00.00.00.0
K2O0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
NiO0.20.20.20.20.20.30.20.20.20.20.20.20.20.20.20.20.2
总量99.199.899.798.399.698.9100.399.299.499.699.7100.199.298.698.999.098.0
Fo83.783.983.883.382.982.583.281.081.381.581.382.280.881.582.080.781.1
微量元素/(μg/g)Li6.623.973.733.253.173.795.016.405.882.264.182.943.386.586.267.275.02
Na47.825.217.415.513.815.220.016.955.17.15.334.820.219.45.4112.022.3
Al60.795.2118.4140.670.670.0119.5129.9108.1186.0121.7320.097.8109.570.198.492.3
P68.658.741.544.147.041.054.879.766.648.480.766.145.263.261.886.349.9
Ca586.079295013086096027331154858324465155082152326313756.0
Sc8.505.993.994.264.924.124.534.663.973.564.165.643.863.483.921.541.51
Ti151.1081225913715378.959.359.947.335.940.486.5106113119130
V6.644.285.645.063.873.995.605.954.675.292.1511.54.904.083.701.301.19
Cr145.0138.3135.1122.171.497.5116.989.782.594.795.2161.780.861.834.983.476.5
Mn1 8821 8441 6741 7051 7061 7011 6862 2041 8891 6001 9771 9551 7721 8211 82016321553
Co166180176180166164171197176162176173167160166107109
Ni1 8341 6681 8701 9061 9732 0501 8702 0512 1251 7831 7621 6521 6381 5051 5231 4181 494
Zn91.298.3103.390.677.480.476.0100.479.085.699.2145.970.956.674.3118.3113.9
Y0.470.350.220.250.600.370.190.950.220.070.120.400.310.190.180.390.19
Zr0.410.040.150.050.350.450.100.170.130.040.020.060.180.260.490.120.08
采样位置I号岩体上部岩相带
样号JC06-234JC06-237JC13-114JC13-116JC13-112JC13-118JC13-121
岩性细粒含硫化物橄榄岩细粒含硫化物橄榄岩细粒含硫化物橄榄岩细粒含硫化物橄榄岩细粒含硫化物橄榄岩细粒二辉橄榄岩细粒橄榄辉石岩
点号Ol-1Ol-2Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3
主量元素质量百分含量/%MgO44.945.143.743.643.143.144.243.742.244.143.944.044.643.742.842.143.942.041.742.2
Al2O30.00.00.00.10.00.10.00.00.00.00.00.00.00.00.00.00.00.00.00.0
SiO240.239.540.640.940.239.940.940.139.338.640.340.240.840.339.440.340.639.138.839.1
CaO0.20.00.00.30.10.30.10.00.10.10.30.00.30.10.10.20.10.10.10.0
TiO20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Cr2O30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
MnO0.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.2
FeO13.413.114.014.114.415.015.014.814.214.414.814.314.914.615.716.515.417.117.117.5
Na2O0.00.00.00.00.00.00.10.00.00.00.00.00.10.00.00.10.00.00.00.0
K2O0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
NiO0.30.20.30.30.20.20.20.20.20.20.20.30.20.20.20.20.20.20.20.2
总量99.298.398.799.698.398.9100.899.296.497.899.899.1101.299.398.699.6100.698.798.299.3
Fo85.686.084.884.784.283.684.084.184.184.584.184.684.284.283.081.983.581.581.381.2
微量元素/(μg/g)Li5.823.9911.937.356.743.413.323.765.934.725.382.625.323.736.164.336.795.324.307.97
Na11.510.925.123.324.786.022.118.6690.016.3224.023.827.914.98.730.210.012.811.318.2
Al120.3126.5164.091.1122.6107.8109.290.989.7136.9114.5118.8151.0101.3142.1173.4161.995.9111.1114.8
P91.880.4204.6105.695.657.750.159.364.150.560.666.470.964.472.456.973.667.947.081.1
Ca9297419792918894336416035407621160867759723858589605900775776
Sc6.266.836.507.056.532.984.974.553.684.533.985.224.614.663.613.823.503.933.714.03
Ti90.413770.513314013778.411816071.174.990.511315236.644.055.069.891.248.8
V4.444.314.653.234.116.825.554.274.464.914.274.914.594.363.874.094.494.983.884.62
Cr123.8126.4127.868.3158.066.2108.982.980.7124.1103.797.886.7105.6105.098.4114.788.082.696.1
Mn1 5961 6801 6161 8231 7601 5861 6571 6021 5891 6211 6141 5991 7361 6421 6251 9311 6261 7981 8101 828
Co16616616499168164173173168168167158176163158170195148157163
Ni2 0812 5281 9611 8192 0032 0261 8531 9351 7471 7651 7822 1522 1382 0171 9211 8261 8731 5591 5331 604
Zn80.867.966.360.970.645.471.182.985.969.282.352.074.197.384.967.557.672.858.757.4
Y0.270.570.430.220.420.200.270.320.240.220.210.380.480.280.070.070.060.560.430.26
Zr0.040.060.070.500.720.320.160.260.230.110.080.190.240.440.020.050.060.130.190.09
采样位置II号岩体
样号JC12-201JC12-207JC13-259JC12-206JC13-258JC13-259JC13-254
岩性中粒橄榄辉石岩中粒硫化物二辉橄榄岩中粒二辉橄榄岩中粒硫化物二辉橄榄岩中粒二辉橄榄岩中粒二辉橄榄岩中粒斜长石二辉橄榄岩
点号Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3Ol-1Ol-2Ol-3

主量元素质量

百分含量/%

MgO44.142.643.443.443.743.642.542.143.241.142.742.342.441.742.742.742.642.142.641.542.4
Al2O30.00.00.00.00.00.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
SiO239.939.339.739.339.439.440.239.240.838.740.138.839.839.639.639.940.738.938.538.540.2
CaO0.00.10.00.00.00.20.20.00.00.00.00.00.00.10.10.00.20.10.10.10.2
TiO20.00.10.10.00.00.00.00.00.00.00.00.00.00.10.00.00.10.00.00.10.1
Cr2O30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.0
MnO0.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.2
FeO15.114.315.615.414.914.916.116.115.617.016.516.716.917.316.316.216.616.417.117.516.6
Na2O0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.00.00.00.00.0
K2O0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
NiO0.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.2
总量98.696.899.398.698.598.699.497.7100.197.299.998.399.699.299.199.3100.597.998.998.499.8
Fo83.984.183.283.483.983.982.582.483.281.282.281.981.781.282.482.582.182.181.680.882.0

微量元素

/(μg/g)

Li4.486.044.763.326.664.786.625.718.2211.973.764.985.534.294.384.816.542.133.784.387.92
Na26.28.212.46.75.27.319.544.58.7372.017.647.612.89.610.114.012.96.533.677.06.3
Al131.875.9107.5101.053.782.3229.062.799.2442.086.987.8112.991.9132.1113.798.887.3101.7123.562.7
P56.889.462.157.984.952.865.455.068.2140.160.459.967.164.970.674.8115.345.247.858.3108.9
Ca10355452773054836176762440452348629665739697788790577327870316323
Sc4.884.703.653.733.444.375.564.074.710.374.714.815.504.826.255.164.655.404.275.763.34
Ti76116160133109781321031515510711311866885395118137100154
V4.732.752.633.421.923.275.762.524.040.865.325.674.834.445.404.283.772.664.564.873.27
Cr106.253.251.168.741.066.0164.045.170.542.1110.975.873.756.572.355.562.147.460.465.127.0
Mn1 7041 6101 6191 5541 5731 6161 6911 7661 6741 6421 7451 7031 7331 6921 7861 7381 6241 5661 8121 7791 729
Co18216716616516817517416917494115103174171170171171179176163189
Ni1 7671 6701 6351 6241 6861 6791 6761 6461 7151 0291 6051 6051 6141 6351 5711 6491 6931 7781 7371 6551 882
Zn100.561.363.965.277.347.573.274.373.072.788.581.997.988.795.674.273.283.074.160.580.9
Y0.560.360.580.120.170.240.700.290.380.110.310.690.540.360.610.540.290.360.390.230.21
Zr0.210.570.300.400.370.250.620.550.570.250.250.300.390.180.210.090.320.560.540.350.44

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3 橄榄石的岩相学特征

橄榄石是金川岩体含辉橄榄岩、二辉橄榄岩和橄榄辉石岩等各个岩相中最主要的造岩矿物。橄榄石通常呈半自形或浑圆粒状,发育堆晶结构和包橄结构(图2a,2b),辉石和斜长石则充填于橄榄石颗粒间(图2c)[39]。金川Ⅰ号岩体上部岩相带中橄榄石粒径主要为1.5~3 mm,个别达3.5 mm,含量随深部增加缓慢增大,粒径基本保持不变;下部岩相带橄榄石粒径为1.5~8 mm,大部分在4~7 mm,个别达10 mm,含量随深度增加先增大再减小,粒径变化较小。金川Ⅱ号岩体橄榄石粒径大小不等,小者1.5~ 2 mm,大者4.0~6.5 mm,一般为2~4 mm,含量由岩体中间向边缘减少,粒径变化不大[39]。橄榄石普遍遭受不同程度的热液蚀变,堆晶橄榄石大部分完全蛇纹石化,同时有磁铁矿的析出;而被单斜辉石包裹的橄榄石则比较新鲜,蚀变相对弱些(图2b)。橄榄石中常含有铬尖晶石的包裹体(图2d)。浸染状矿化中硫化物呈彼此不连续状分布于橄榄石颗粒间(图2e),而网脉状矿化中堆晶橄榄石颗粒被硫化物包裹(图2f)。

4 分析方法

样品磨制成薄片后,在显微镜下观察选择新鲜的橄榄石进行主量及微量元素分析。测试点均位于橄榄石颗粒的核部,同时避开表面凹坑和裂纹。橄榄石主量元素分析在中国科学院地球化学研究所矿床地球化学国家重点实验室电子探针实验室完成。分析仪器型号为EPMA-1600型电子探针,束斑直径为10 μm,电流为20 nA,加速电压为15 kV。校准用SPI标准矿物,分析误差小于5%,分析结果列于表1

橄榄石微量元素分析在中国科学院地球化学研究所矿床地球化学国家重点实验室LA-ICP-MS实验室完成。LA-ICP-MS由Agilent 7700 cs四级杆ICP-MS连接于GeoLasPro193 nm激光剥蚀系统上组成。测试时仪器状态如下:激光束斑直径为44 μm,激光脉冲频率为6 Hz,脉冲能量为0.032~0.105 MJ,分析时间为90 s(30 s空白测试和60 s样品分析)。测试过程中,激光剥蚀点位均与电子探针分析点位重合。内标NIST 610和NIST 612每隔9个橄榄石样品被分析1次用来监控仪器偏差。国际标样ML3B-G和BCR-2G被做为未知样去监控数据质量(图3)。数据处理使用Igor-pro(http://www.wavemetrics.com)软件通过电子探针分析获得的Si元素含量为内标校准得到。标样GOR128-G,BIR-1G,BHVO-2G,ML3B-G和BCR-2G的分析结果能很好地一致于其参考值,除Cr,Y和Zr(10%~15%)以外,各元素分析误差均小于10%(表1)。

图3

图3   LA-ICP-MS标样分析结果与推荐值比较

Fig.3   Comparison of LA-ICP-MS analytical results with their preferred values

标样推荐值来自“GeoREM database”(http://georem.mpch-mainz.gwdg.de/sample_query_pref.asp)

The preferred values from the “GeoREM database”(http://georem.mpch-mainz.gwdg.de/sample_query_pref.asp)


5 分析结果

电子探针分析结果得到的金川橄榄石的Fo值80.7~86.0,与前人分析的结果基本一致[5,8,41,42]。Li等[8,19]得到的金川岩体原生橄榄石Fo值为81~85.5,而与阳起石化蚀变有关的重结晶橄榄石Fo值为76~81。本次分析得到的橄榄石高Fo值与前人的分析基本一致,但低值要高一些,与本次研究的样品蚀变相对较弱有关。

虽然金川橄榄石微量元素含量具有较大的变化范围,但仍具一定的变化规律。橄榄石成分随岩相的变化:橄榄岩相中包含最富MgO的橄榄石,但其微量元素变化范围较小,通常含有较高的Ni和Cr含量;二辉橄榄岩相中具最大变化范围的微量元素分布;斜长石二辉橄榄岩相中则具最低的Ni和Cr含量。显示为橄榄岩中的橄榄石具较高的Ni,Cr和Ca的含量,较低的Zn,Mn和Co的含量(图4)。橄榄石成分随岩体空间的变化:I号岩体下部岩相带粗粒橄榄石中Ni,Cr,Mn,Zn,Ti和Ca的变化范围较大,而上部岩相带细粒橄榄石显示最大变化的Fo值以及Ni和Co的含量。II号岩体橄榄石微量元素含量变化范围较小,且Cr,V和Zn含量偏低(图4)。

图4

图4   橄榄石中微量元素在岩体和岩相间的变化

Fig.4   Variation of trace elements in olivines with intrusion and petrofacies

WI-LN:Ⅰ号岩体下部岩相带;WI-UN:Ⅰ号岩体上部岩相带;EI:Ⅱ号岩体;Du:纯橄岩;Lh:二辉橄榄岩;Pl-Lh:斜长二辉橄榄岩

WI-LN: The Lower unit of intrusion Ⅰ;WI-UN: The Upper unit of intrusion Ⅰ;EI: The intrusion Ⅱ;Du: Dunite;Lh: Lherzolite;Pl-Lh: Plagioclase lherzolite


在原始地幔橄榄石[43,44]多元素标准化图中,金川橄榄石具显著的Cr,V,Ni和Co的负异常以及轻微的Ti亏损(图5)。金川I号和II号岩体橄榄石具相似的元素配分模式,其成分从Zr到Sc变化程度相较于从V到Ni变化大,显著富集不相容元素Zr,Y,Ti,Sc和Ca的特征。橄榄石中Cr元素含量变化范围为34~158 μg/g,随着橄榄石Fo值降低其含量不断减小(图6a);Cr与V具弱正相关关系(图6b)。Ni元素含量变化范围为1 029~2 528 μg/g,Ni与Fo呈负相关关系(图6c),即随着橄榄石Fo值的降低,Ni含量逐渐减少;Co元素含量变化范围为98~197 μg/g,随着Fo值降低其含量基本不变(图6d);Ni与Co之间具弱正相关关系(图6e)。Mn元素含量变化范围为1 553~2 204 μg/g,Zn元素含量变化范围为45.4~118.3 μg/g,橄榄石中Mn/Fe比与Fo具正相关的关系(图7a),Mn/Zn和Zn/Fe则无明显相关性(图7b和7c),同时Zn与Mn也具正相关关系(图7d)。

图5

图5   金川超镁铁质岩体橄榄石中主要微量元素标准化蛛网图

Fig.5   The original mantle olivine-normalized trace element patterns of the Jinchuan intrusion

原始地幔橄榄石成分引自参考文献[43,44],金川数据为每个样品平均的橄榄石成分 WI-LN:Ⅰ号岩体下部岩相带;WI-UN:Ⅰ号岩体上部岩相带;EI:Ⅱ号岩体

The composition of the original mantle olivine comes from references[43,44] and the average composition of each sample was reflected in this figure WI-LN: The Lower unit of intrusion Ⅰ;WI-UN: The Upper unit of intrusion Ⅰ;EI: The intrusion Ⅱ


图6

图6   金川超镁铁质岩体中橄榄石Fo与微量元素二元相关图

Fig.6   Plots of selected trace elements vs. forsterite content of analyzed olivine

FC-1,FC-2和FC-3指估算的瑞利分离模式线;数字0和5分别代表岩浆初始结晶和已有5%的固相从岩浆中晶出时的状态;FC-1模式线指岩浆中仅橄榄石结晶;FC-2模式线指橄榄石和铬尖晶石以15∶1的比例从岩浆中共结;FC-3模式线指橄榄石和硫化物以45∶1从岩浆中共结; WI-LN:Ⅰ号岩体下部岩相带;WI-UN:Ⅰ号岩体上部岩相带;EI:Ⅱ号岩体

FC-1, FC-2 and FC-3 denotes that calculated Rayleigh fractionation model lines; Number 0 and 5 represent respectively the state of magmatic crystallization from parental magma. FC-1 indicates the only crystallization of olivine from a parental melt; FC-2 indicates the crystallization of olivine:Spinel, in a ratio of 15∶1 from a parental melt; FC-3 indicates the crystallization of olivine:Sulfide, in a ratio of 45∶1 from a parental melt WI-LN: The Lower unit of intrusion Ⅰ;WI-UN: The Upper unit of intrusion Ⅰ;EI: The intrusion Ⅱ


图7

图7   金川超镁铁质岩体橄榄石微量元素地幔源区的判别图(据参考文献 [32,45] 修改)

Fig.7   Discrimination diagrams for the mantle sources of the Jinchuan ultramafic intrusion using the trace elements in olivine (modified after references [32,45])

洋中脊玄武岩和科马提岩数据引自参考文献 [32], WI-LN:Ⅰ号岩体下部岩相带;WI-UN:Ⅰ号岩体上部岩相带;EI:Ⅱ号岩体;MORB: 洋中脊玄武岩;KOMATIITES: 科马提岩

Dates of MORB and Komatiites come from reference [32],WI-LN: The Lower unit of intrusion Ⅰ;WI-UN: The Upper unit of intrusion Ⅰ;EI: The intrusion Ⅱ; MORB: Mid-Ocean Ridge Basalt; KOMATIITES: Komatiites


6 讨 论

岩浆中微量元素的行为遵循亨利定律,因此,在岩浆演化矿物结晶时,可以用瑞利分离定律来描述熔体中微量元素的地球化学行为:

CL=CO×F(D-1)

式中:CL为微量元素在熔体中的浓度;CO为微量元素在原始熔体中的浓度;F为原始熔体中分离结晶作用后剩余的部分;D为元素在结晶相与熔体之间的总分配系数。当岩浆中结晶矿物相发生变化时,需要重新计算CLCOD值以便模拟进一步的分异。由于金川岩体母岩浆为高MgO的玄武质岩浆[5,13,19],因此,选择大陆裂谷系统下高镁玄武岩[46]中的微量元素含量作为初始熔体的CO值。矿物从熔体中晶出的顺序和比例[8,14,19,47]可以在给定的母岩浆成分下利用熔浆热力学软件(MELTS)[48,49]在合理的温压状况下获得。微量元素在玄武质熔体与橄榄石、铬尖晶石和硫化物中的分配系数见表2。假设金川母岩浆分离结晶过程中橄榄石—岩浆的Mg-Fe分配系数保持恒定(KD=(FeO/MgO)Ol/(FeO/MgO)L=0.3±0.003[56]),分离结晶的固相以1%的比例从残余熔体中快速晶出以保证使硅酸盐熔体产生最大的成分变化。

表2   微量元素Cr, V, NiCo的分配系数和Co

Table 2  Distribution coefficients and Co values of trace elements Cr, V, Ni and Co

CrVNiCo
D硫化物0.90.650070
D橄榄石0.90.0973.2
D尖晶石240624.6
Co/(μg/g)1805030060

注:分配系数引自参考文献[43,44,50~55],Co值引自参考文献[46]

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岩浆硫化物含矿岩体中影响橄榄石成分的因素主要有以下几个方面:母岩浆成分;岩浆结晶分异作用和硫化物熔离作用;橄榄石与后期的晶间硅酸盐岩浆以及硫化物熔体的反应[41]。金川岩体橄榄石成分(Fo和Ni)研究表明母岩浆在深部发生了少量橄榄石的先期结晶,进入到浅部岩浆房后堆晶的橄榄石又与硅酸盐/硫化物熔体发生了相互反应[8,41,57]。结合前人的研究工作,下面利用橄榄石微量元素(Ni,Co,V,Cr,Mn和Zn)进一步讨论金川矿床分离结晶、硫化物熔离和地幔源区特征等关键成矿要素。

6.1 橄榄石与铬尖晶石共结

金川橄榄石相较于原始地幔橄榄石,显示Cr和V的负异常(图5)。因为元素Cr和V在铬尖晶石中强烈相容[58],因此,当岩浆演化过程中结晶铬尖晶石时会使熔体中这些元素含量降低,从而结晶的橄榄石也必然具低的Cr和V含量。可以看到,当金川母岩浆结晶少量铬尖晶石(橄榄石:铬尖晶石=15∶1)时模拟曲线(FC-2)能较好地满足Cr和Cr-V元素的变化趋势(图6a,6b);但岩浆分异晚期(分离结晶量大于5%)结晶的橄榄石中V元素明显低于模拟演化线。因为元素V在橄榄石和玄武质熔体中的分配行为主要受其价态的影响且V3+优先分配进入橄榄石中[59,60,61];因此,当岩浆体系中氧逸度发生变化时会导致熔体中V3+/V4+的比值发生变化。金川岩体晚期结晶的橄榄石中偏低的V含量可能暗示着熔体中V3+/V4+的比值降低,这可能与体系中氧逸度升高有关。金川岩体橄榄石与硫化物的Fe-Ni交换反应表明其具较高的氧逸度(QFM+0.5~QFM+1)[9,14,24,62,63],同时斜长二辉橄榄岩相中出现岩浆成因的磁铁矿和钛铁矿等副矿物[39];表明金川母岩浆演化晚期有可能结晶少量Fe-Ti氧化物。这会导致晚期岩浆中V含量降低,进而结晶的橄榄石也具低的V含量。

在多元素标准化图中金川橄榄石同时体现出弱Ti的负异常(图5),而这可能也与共结的铬尖晶石相关。金川铬尖晶石具相对高的Ti含量,可见明显的钛铁晶石的出熔条纹[64,65],这表明铬尖晶石结晶时Ti以内置同相的形式进入到其晶格中[66]。虽然元素Ti在铬尖晶石中为中等—弱不相容元素(Dsp/melt = 0.4~0.9[58]),但纯橄岩中铬尖晶石分布密集的出熔条纹暗示着岩浆中Ti置换进入到铬尖晶石晶格中的程度较高,这会导致岩浆中Ti元素含量降低,进而使共结的橄榄石中Ti元素偏低。

6.2 橄榄石结晶与硫化物熔离作用

与原始地幔橄榄石相比,金川橄榄石显示Ni和Co的负异常(图5)。这些负异常可能是由于母岩浆进入浅部岩浆房之前发生了硫化物的早期熔离造成的,因为Ni和Co在硫化物熔体中是强相容元素(DNiSul/Liq = 500~800, DCoSul/Liq = 61~80[67])。另外,Ni和Co负异常也可能是母岩浆中亏损这些元素导致的,因为岩浆演化过程中发生的早期橄榄石的分离结晶会使母岩浆亏损这些元素(DNiOl/Liq = 22.3±9.12, DCoOl/Liq = 5.2±1.5[68])。MELTS热力学计算表明金川母岩浆侵位前在深部发生了少量橄榄石(3%~4%)的先期结晶[8,47],但相对小的分离结晶量不足以造成观察到的橄榄石中显著的Ni和Co异常。相反,金川岩体母岩浆中Ir和Pd含量明显低于平均高镁玄武岩(MgO = 12%)中的Ir和Pd含量[19,40],暗示着发生了早期的硫化物熔离作用。硫化物熔离可使岩浆中Ni和Co等亲铜元素显著亏损,导致结晶出的橄榄石也必然是Ni和Co亏损的。金川矿床硫化物中低的PGE品位暗示经历了硫化物的二次熔离作用[13,40],硫化物在深部的早期熔离会使母岩浆亏损Ni和Co元素;当母岩浆进入浅部岩浆房后,硫化物与橄榄石的共沉淀同样会对橄榄石中Ni和Co元素产生影响。

金川岩体大部分橄榄石Ni含量落于模式曲线FC-1之下(图6c),表明橄榄石是从硫饱和的岩浆中结晶出来的;大部分橄榄石Ni和Co含量位于模拟曲线FC-1和FC-3之间,表明橄榄石中Ni和Co含量变化主要受橄榄石结晶分异和硫化物不混溶作用共同控制,橄榄石结晶和硫化物熔离同时进行时橄榄石和硫化物的质量比值约为451(图6c,图6d)。但仍有部分橄榄石Ni和Co元素数据点位于模拟曲线外,这可能与硫化物和橄榄石间发生的Fe-Ni(Co)交换反应有关。岩浆硫化物矿床中橄榄石与硫化物间的元素交换反应很普遍,在Voisey’s Bay、我国黄山岩带以及北山地区的岩浆硫化物矿床中均有报道[29,69,70,71,72,73]

金川I号岩体上部岩相带来自于PGE未亏损的岩浆,下部岩相带和II号岩体母岩浆在侵位前均经历了少量硫化物的早期熔离[13]。因此,I号岩体上部岩相带底部高Fo橄榄石的Ni和Co含量基本能够代表浅部岩浆房中橄榄石初始的Ni和Co含量。I号岩体上部岩相带是含橄榄石—斜方辉石的“晶粥”侵入到浅部岩浆房分异—堆晶的结果[12],因此,岩浆房中先结晶的橄榄石会与晶间硅酸盐岩浆发生反应导致其Fo值变低,并且橄榄石中Ni和Co含量也因与硫化物熔体之间的Fe-Ni(Co)交换而升高。但I号岩体上部岩相带矿化很弱,仅在底部可见稀疏浸染状的矿化,意味着硫化物熔体与橄榄石间的Fe-Ni(Co)交换反应较弱,这使得橄榄石更易于保存相对原始的Ni和Co含量。相反,I号岩体下部岩相带和II号岩体网脉状矿石的形成是由于熔离的硫化物置换堆晶橄榄石间隙的硅酸盐熔体造成的[18],硫化物在橄榄石颗粒间很好的连通性预示着硫化物可以与橄榄石发生广泛的Fe-Ni(Co)交换反应,这会导致网脉状矿石中橄榄石的Ni和Co含量更易被改变。因此,更强烈的Fe-Ni(Co)交换反应可能是导致I号岩体下部岩相带和II号岩体中的橄榄石有更多的数据点位于模拟演化线(FC-1)之上的原因。

6.3 橄榄石微量元素对成岩与成矿作用的指示

橄榄石微量元素标准化图解中显示出金川I号和II号岩体橄榄石具相似的配分模式(图5),暗示I号和II号岩体具相同的母岩浆成分,但I号和II号岩体在岩相、地球化学特征上具明显的差异。II号岩体橄榄石粒径呈中—细粒状;而I号岩体上部岩相带橄榄石呈细粒状,下部岩相带橄榄石则呈粗粒状[39];II号岩体相较于I号岩体具更高的Cu/Pd比值和更低的PGE含量[13,40]。这些特征表明金川I号和II号岩体经历了不同的成岩与成矿过程。

在Cr-V相关图上(图6b),II号岩体橄榄石具相对低的Cr和V含量,模拟演化线上显示结晶II号岩体的岩浆更加演化。金川岩体橄榄石颗粒粒径统计表明I号岩体粗粒橄榄石经历了2期成核生长,即岩浆上升过程中搬运深部结晶的橄榄石在浅部岩浆房中继续生长;II号岩体中橄榄石则经历了1期的成核生长,即橄榄石以浅部岩浆房中原地生长为主[18]。因此,橄榄石结晶的相对早晚可能是造成I号和II号岩体橄榄石中Cr和V含量差异的主要原因。在Ni-Co相关图上(图6e),II号岩体较I号岩体具更低变化的Ni和Co含量,表明矿物结晶或与粒间熔体反应时DNi/DCo相对恒定,这可能与成矿作用过程中岩浆的多次补充以及硫化物熔体的分异相关。尽管金川I号岩体上部、下部岩相带是不同期次的岩浆演化的产物[13],但二者的橄榄石微量元素特征差别较小,主要区别表现为下部岩相带较上部岩相带具变化更大的Mn和Ca含量(图4),这可能与下部岩相带遭受更强的热液蚀变有关。

6.4 橄榄石微量元素对地幔源区的指示

已有研究认为金川岩体岩浆起源于被地幔柱加热的异常富集的岩石圈地幔,并认为这种富集地幔的熔融对金川矿床的形成起了至关重要的作用[20,22]。近年来,橄榄石微量元素特征可以有效的示踪幔源岩浆源区的性质[31,32,33,34,74]。如Sobolev等[32,75]研究发现大陆溢流玄武岩中橄榄石斑晶的Mn含量低于洋中脊玄武岩中橄榄石斑晶,认为这一特征反映了二者地幔源区成分存在差异,前者起源于辉石岩地幔,后者是橄榄岩源区部分熔融的产物。类似地,西伯利亚大陆溢流玄武岩和Noril’sk硫化物矿床中橄榄石比MORB中橄榄石的Mn含量偏低,是由于前二者起源于辉石岩地幔源区所致[74]。Jin等[76]研究塔里木大火成岩省中瓦吉里塔格岩体时认为橄榄辉石岩中橄榄石具相对低的Mn含量,同样是由于源区存在辉石岩组分导致的。金川岩体橄榄石较MORB橄榄石具相对低的Mn含量(图7a),暗示金川岩体源区也许可能有辉石岩组分的存在。Tonnelier[42]根据金川橄榄石较低的Mn含量和较高的Ni含量认为其源区为辉石岩地幔。

然而,橄榄石的实验岩石学研究认为高Ni含量、低Mn/Fe值的橄榄石也可以由橄榄岩源区在高压熔融时产生[34,72,77]。因此,地幔熔融深度不同会导致橄榄石中Ni和Mn元素含量产生差异。金川岩体橄榄石较低的Fo值(最高Fo值为86)表明岩体侵位前母岩浆经历了一定程度的演化,这使最原始的橄榄石Ni和Mn元素含量很难确定。其次,金川橄榄石Mn/Fe值体现出与Fo具正相关关系(图7a)也暗示岩浆演化对微量元素Mn的影响。

相反,金川超基性岩体的源区更可能为橄榄岩地幔(图7)。Howarth等[45]在研究Karoo和Etendeka大陆溢流玄武岩时指出利用橄榄石Mn/Zn和Zn/Fe比值也可以有效区分地幔源区,在Fo~Mn/Zn和Fo~10 000×Zn/Fe图解(图7b,7c)中金川岩体基本落入橄榄岩地幔源区范围内。橄榄石中Mn/Zn和Zn/Fe值与Fo无相关性(图7b,7c),表明岩浆演化不会对其产生影响。金川岩体侵位前母岩浆虽然经历了5%~20%的上地壳物质的同化混染[14,19],但平均上地壳Mn(600 μg/g)和Zn(70 μg/g)[78]含量相较于熔体中明显偏低。因此,同化混染作用对熔体中Mn/Zn和Zn/Fe值的影响可以忽略不计。与粒间熔体的反应虽然会使橄榄石中Mn和Zn含量降低,但仍然不会改变Mn与Zn正相关的关系(图7d)。综上所述,橄榄石的Mn/Zn(>13)和Zn/Fe(<11)值特征指示了金川岩体母岩浆起源于橄榄岩地幔,而非前人提出的辉石岩的地幔源区[42]

7 结 论

(1)金川岩体中橄榄石微量元素含量变化范围较大;其变化主要受铬尖晶石共结和熔离硫化物的控制:与铬尖晶石的共结使橄榄石亏损Cr,V和Ti元素;硫化物的熔离及其与橄榄石的相互反应共同影响着橄榄石中Ni和Co元素的含量。

(2)金川I号和II号岩体中橄榄石显示出相同的微量元素标准化配分模式,暗示二者具相似的母岩浆组成,是同一个岩浆通道系统内的产物。

(3)金川岩体中橄榄石高的Mn/Zn和低的Zn/Fe值表明金川岩体母岩浆可能起源于橄榄岩地幔,而非前人提出的辉石岩地幔源区。

参考文献

Naldrett A J .

Magmatic Sulfide Deposits: Geology, Geochemistry and Exploration

[M]. Berlin Heidelberg: Springer2004.

[本文引用: 1]

Naldrett A J .

Fundamentals of magmatic sulfide deposits

[J]. Reviews in Economic Geology, 2011171): 1-50.

[本文引用: 1]

Song Xieyan , Hu Ruizhong , Chen Liemeng .

Characteristics and inspirations of the Ni-Cu sulfide deposits in China

[J]. Journal of Nanjing University (Natural Science), 2018, 54(2): 221-234.

[本文引用: 1]

宋谢炎, 胡瑞忠, 陈列锰 .

中国岩浆铜镍硫化物矿床地质特点及其启示

[J].南京大学学报:自然科学, 2018, 54(2): 221-234.

[本文引用: 1]

Tang Zhongli .

Metallogenic model of Jinchuan Ni-Cu sulfide deposit

[J]. Geoscience, 1990,(4): 55-64.

[本文引用: 2]

汤中立 .

金川硫化铜镍矿床成矿模式

[J].现代地质, 1990,(4): 55-64.

[本文引用: 2]

Chai Gang , Naldrett A J .

The Jinchuan ultramafic intrusion: Cumulate of a High-Mg basaltic magma

[J]. Journal of Petrology, 1992, 33(2): 277-303.

[本文引用: 4]

Chai Gang , Naldrett A J .

Characteristics of Ni-Cu-PGE mineralization and genesis of the Jinchuan deposit, Northwest China

[J]. Economic Geology, 1992, 87(6): 1 475-1 495.

[本文引用: 2]

Tang Zhongli .

Metallogenic Model and Geological Comparison of Jinchuan Ni-Cu-(Pt) Deposit

[M].Beijing: Geological Publishing House,1995.

[本文引用: 2]

汤中立 .

金川铜镍硫化物{(含铂)}矿床成矿模式及地质对比

[M]. 北京: 地质出版社, 1995.

[本文引用: 2]

Li Chusi , Xu Zhanghua , Waal S A D , et al .

Compositional variations of olivine from the Jinchuan Ni-Cu sulfide deposit, western China: Implications for ore genesis

[J]. Mineralium Deposita, 2004, 39(2): 159-172.

[本文引用: 6]

Lehmann J , Arndt N , Windley B , et al .

Field relationships and geochemical constraints on the emplacement of the Jinchuan intrusion and its Ni-Cu-PGE sulfide deposit, Gansu, China

[J]. Economic Geology, 2007, 102(1): 75-94.

[本文引用: 3]

Hu Peiqing , Zhang Mingjie , Li Chusi , et al .

Noble gas isotopic constraints on the origin of fluids in the Jinchuan Ni-Cu sulfide deposit, Western China

[J]. Geochmica et Cosmochimica Acta, 2008, 72(12): 481-493.

[本文引用: 1]

Zhang Mingjie , Kamo S K , Li Chusi , et al .

Erratum to: Precise U-Pb zircon-baddeleyite age of the Jinchuan sulfide ore-bearing ultramafic intrusion, western China

[J]. Mineralium Deposita, 2010, 45(2): 3-9.

[本文引用: 2]

Song Xieyan , Keays R R , Chen Liemeng , et al .

Structural, lithological, and geochemical constraints on the dynamic magma plumbing system of the Jinchuan Ni-Cu sulfide deposit, NW China

[J]. Mineralium Deposita, 2012, 47(3): 277-297.

[本文引用: 5]

Chen Liemeng , Song Xieyan , Keays R R , et al .

Segregation and fractionation of magmatic Ni-Cu-PGE sulfides in the Western Jinchuan intrusion, northwestern China: Insights from platinum group element geochemistry

[J]. Economic Geology, 2013, 108(8): 1 793-1 811.

[本文引用: 11]

Duan Jun , Chusi Li, Qian Zhuangzhi , et al .

Multiple S isotopes, zircon Hf isotopes, whole-rock Sr-Nd isotopes, and spatial variations of PGE tenors in the Jinchuan Ni-Cu-PGE deposit, NW China

[J]. Mineralium Deposita, 2016, 51(4): 557-574.

[本文引用: 5]

Yang Shenghong , Yang Gang , Qu Wenjun , et al .

Pt-Os isotopic constraints on the age of hydrothermal overprinting on the Jinchuan Ni-Cu-PGE deposit, China

[J]. Mineralium Deposita, 2017,(1): 1-18.

[本文引用: 1]

Waal S A D , Xu Zhanghua , Li Chusi ,et al .

Emplacement of viscous mushes in the Jinchuan ultramafic intrusion, western China

[J]. Canadian Mineralogist, 2004, 42(2): 371-392.

[本文引用: 1]

Chen Liemeng , Song Xieyan , Danyushevsky L V , et al .

A laser ablation ICP-MS study of platinum-group and chalcophile elements in base metal sulfide minerals of the Jinchuan Ni-Cu sulfide deposit, NW China

[J]. Ore Geology Reviews, 2015, 65(3): 955-967.

[本文引用: 3]

Mao Yajin , Barnes S J , Duan Jun , et al .

Morphology and particle size distribution of olivines and sulphides in the Jinchuan Ni-Cu sulphide deposit: Evidence for sulphide percolation in a crystal mush

[J]. Journal of Petrology, 2018, 59(9): 1 701-1 730.

[本文引用: 4]

Li Chusi , Ripley E M .

The giant Jinchuan Ni-Cu-(PGE) deposit: Tectonic setting, magma evolution, ore genesis and exploration implications

[J]. Economic Geology, 2011, 17(2): 163-180.

[本文引用: 7]

Jiao Jian'gang , Liu Huan , Duan Jun , et al .

Hf isotope geochemical characteristics and magma sources in Jinchuan Cu-Ni sulfide deposite

[J]. Journal of Earth Sciences and Environment, 2014, 36(1): 58-67.

[本文引用: 4]

焦建刚, 刘欢,段俊, .

金川铜镍硫化物矿床Hf同位素地球化学特征与岩浆源区

[J]. 地球科学与环境学报, 2014, 36(1): 58-67.

[本文引用: 4]

Chen Liemeng , Song Xieyan , Nie Xiaoyong , et al .

Mineral chenistry and geological significance of pyroxene from segment Ⅱof the Jinchuan intrusion, Gansu Province

[J]. Mineral Petrology, 2008, 28(1): 88-96.

[本文引用: 1]

陈列锰, 宋谢炎, 聂晓勇, .

甘肃金川Ⅱ号岩体辉石化学特征及其地质意义

[J]. 矿物岩石, 2008, 28(1): 88-96.

[本文引用: 1]

Li Xianhua , Su long , Sunlong Chung , et al .

Formation of the Jinchuan ultramafic intrusion and the world's third largest Ni‐Cu sulfide deposit: Associated with the ∼825 Ma south China mantle plume?

[J]. Geochemistry Geophysics Geosystems, 2005, 6(11): 1-16.

[本文引用: 2]

Song Xieyan , Zhou Meifu , ChristineYanWang, et al .

Role of crustal contamination in formation of the Jinchuan intrusion and its world-class Ni-Cu-(PGE) sulfide deposit, Northwest China

[J]. International Geology Review, 2006, 48(12): 1 113-1 132.

[本文引用: 1]

Tang Qingyan , Bao Jiao , Dong Yongxi , et al .

Mg-Sr-Nd isotopic constraints on the genesis of the giant Jinchuan Ni-Cu-(PGE) sulfide deposit, NW China

[J]. Earth and Planetary Science Letters, 2018, 502: 221-230.

[本文引用: 2]

Li Shibin .

Magmatic Evolution and the Formation of Ni-Cu Sulfide Ore Bodies in Segment Ⅱ of the Jinchuan Intrusion

[D]. Beijing:University of Chinese Academy of Sciences,2008.

[本文引用: 1]

李士彬 .

甘肃金川II号岩体岩浆演化及铜镍硫化物成矿过程探讨

[D]. 北京中国科学院大学, 2008.

[本文引用: 1]

Chen Liemeng .

Features and Genesis of Segment Ⅰand Its Hosted Ni-Cu Sulfide Deposits of the Jinchuan Intrusion, Gansu Province

[D].Beijing:University of Chinese Academy of Sciences,2009.

[本文引用: 3]

陈列锰 .

甘肃金川Ⅰ号岩体及其铜镍硫化物矿床特征和成因

[D]. 北京中国科学院大学, 2009.

[本文引用: 3]

Li C , Ripley E M , Maier W D , et al .

Olivine and sulfur isotopic compositions of the Uitkomst Ni-Cu sulfide ore-bearing complex, South Africa: Evidence for sulfur contamination and multiple magma emplacements

[J]. Chemical Geology, 2002, 188(3): 149-159.

[本文引用: 1]

Maier W D , Barnes S J , Sarkar A , et al .

The Kabanga Ni sulfide deposit, Tanzania: I. Geology, petrography, silicate rock geochemistry, and sulfur and oxygen isotopes

[J]. Mineralium Deposita, 2010, 45(5): 419-441.

[本文引用: 1]

Deng Yufeng , Song Xieyan , Zhou Taofa , et al .

Correlations between Fo number and Ni content of olivine of the Huangshandong intrusion, eastern Tianshan, Xinjiang, and the genetic significances

[J]. Acta Petrologica Sinica, 2012, 28(7): 280-290.

[本文引用: 2]

邓宇峰,宋谢炎,周涛发, .

新疆东天山黄山东岩体橄榄石成因意义探讨

[J]. 岩石学报, 2012, 28(7): 280-290.

[本文引用: 2]

Li Chusi , Naldrett A J , Ripley E M .

Controls on the Fo and Ni contents of olivine in sulfide-bearing mafic/ultramafic intrusions: Principles, modeling, and examples from Voisey's Bay

[J]. Earth Science Frontiers, 2007, 14(5): 177-183.

[本文引用: 1]

Sobolev A V , Hofmann A W , Sobolev S V , et al .

An olivine-free mantle source of Hawaiian shield basalts

[J]. Nature, 2005, 434(7 033): 590-597.

[本文引用: 2]

Sobolev A V , Hofmann A W , Kuzmin D V , et al .

The amount of recycled crust in sources of mantle-derived melts

[J]. Science, 2007, 316(5 823): 412-417.

[本文引用: 7]

Foley S F , O’Neill H S C .

Trace element variations in olivine phenocrysts from Ugandan potassic rocks as clues to the chemical characteristics of parental magmas

[J]. Contributions to Mineralogy and Petrology, 2011, 162(1): 1-20.

[本文引用: 3]

Foley S F , Prelevic D , Rehfeldt T , et al .

Minor and trace elements in olivines as probes into early igneous and mantle melting processes

[J]. Earth and Planetary Science Letters, 2013, 363(2): 181-191.

[本文引用: 4]

Zhang Liuyi , Li Ni , Prelevic Dejan .

The research status of olivine trace elements in-situ analysis and perspectives if its application

[J]. Acta Petrologica Sinica, 2016, 32(6): 1 877-1 890.

[本文引用: 1]

张柳毅, 李霓, Prelevic Dejan .

橄榄石微量元素原位分析的现状及其应用

[J]. 岩石学报, 2016, 32(6): 1 877-1 890.

[本文引用: 1]

Neave D A , Shorttle O , Oeser M , et al .

Mantle-derived trace element variability in olivines and their melt inclusions

[J]. Earth and Planetary Science Letters, 2018, 483: 90-104.

[本文引用: 1]

Zhang Ruigang , Gao Xue , Yang Liqiang .

Indentification of magma mixing: A case study of the daocheng bathlith in the Yidun Arc

[J]. Advance in Earth Science, 2018, 33(10): 1 058-1 074.

[本文引用: 1]

张瑞刚, 高雪, 杨立强 .

岩浆混合作用的识别: 以义敦岛弧稻城岩体为例

[J]. 地球科学进展, 2018, 33(10): 1 058-1 074.

[本文引用: 1]

Spandler C , O’Neill H S C , Kamenetsky V S .

Survival times of anomalous melt inclusions from element diffusion in olivine and chromite

[J]. Nature, 2007, 447(7 142): 303-306.

[本文引用: 1]

Geological Survey of Gansu Province, Geological Sixth .

Geology of the Baijiazuizi Cu-Ni Sulfide Deposit

[M]. Beijing:Geoligical Publishing House, 1984.

[本文引用: 9]

甘肃省地质矿产局第六地质队 .

白家咀子硫化铜镍矿床地质

[M]. 北京:地质出版社, 1984.

[本文引用: 9]

Song Xieyan , Keays R R , Zhou Meifu , et al .

Siderophile and chalcophile elemental constraints on the origin of the Jinchuan Ni-Cu-(PGE) sulfide deposit, NW China

[J]. Geochimica et Cosmochimica Acta, 2009, 73(2): 404-424.

[本文引用: 4]

Chen Liemeng , Song Xieyan , Danyushevsky L V , et al .

Correlation between Ni and MgO contents of olivine in segment Ⅰ of the Jinchuan intrusion, NW China, and its geological implication

[J]. Acta Petrologica Sinica, 2009, 25(12): 3 369-3 378.

[本文引用: 3]

陈列锰,宋谢炎, Danyushevsky L V , .

金川Ⅰ号岩体橄榄石Ni-MgO相互关系及其地质意义

[J]. 岩石学报, 2009, 25(12): 3 369-3 378.

[本文引用: 3]

Tonnelier N J .

Geology and Genesis of the Jinchuan Ni-Cu-(PGE) Deposit, China

[D]. Canada: Laurentian University,2010.

[本文引用: 3]

Bulle F , Layne G D .

Trace element variations in olivine from the eastern Deeps intrusion at Voisey's Bay, Labrador, as a monitor of assimilation and sulfide saturation processes

[J]. Economic Geology, 2015, 110(3): 713-731.

[本文引用: 3]

Bulle F , Layne G D .

Multi-element variations in olivine as geochemical signatures of Ni-Cu sulfide mineralization in mafic magma systems—Examples from Voisey’s Bay and Pants Lake intrusions, Labrador, Canada

[J]. Mineralium Deposita, 2016, 51(1): 49-69.

[本文引用: 3]

Howarth G H , Harris C .

Discriminating between pyroxenite and peridotite sources for Continental Flood Basalts (CFB) in southern Africa using olivine chemistry

[J]. Earth and Planetary Science Letters, 2017, 475: 143-151.

[本文引用: 3]

Shirey S B , Klewin K W , Berg J H , et al .

Temporal changes in the sources of flood basalts: Isotopic and trace element evidence from the 1100 Ma old Keweenawan Mamainse Point Formation, Ontario, Canada

[J]. Geochimica et Cosmochimica Acta, 1994, 58(20): 4 475-4 490.

[本文引用: 2]

Chen Liemeng , Song Xieyan , Danyushevsky L V , et al .

Parental magma compositions of the Jinchuan intrusion,Gansu Province and MELTS thermodynamic modelling of fractional crystallization

[J]. Acta Geologica Sinica, 2009, 83(9): 1 302- 1 315.

[本文引用: 2]

陈列锰,宋谢炎, Danyushevsky L V , .

金川岩体母岩浆成分及其分离结晶过程的熔浆热力学模拟

[J]. 地质学报, 2009, 83(9): 1 302-1 315.

[本文引用: 2]

Ghiorso M S , Sack R O .

Chemical mass transfer in magmatic processes IV: A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures

[J]. Contributions to Mineralogy and Petrology, 1995, 119(2/3): 197-212.

[本文引用: 1]

Asimow P D , Ghiorso M S .

Algorithmic modifications extending MELTS to calculate subsolidus phase relations

[J]. American Mineralogist, 1998, 83(9/10): 1 127-1 132.

[本文引用: 1]

Rajamani V , Naldrett A J .

Partitioning of Fe, Co, Ni, and Cu between sulfide liquid and basaltic melts and the composition of Ni-Cu sulfide deposits

[J]. Economic Geology, 1978, 73: 82-93.

Beattie P .

Systematics and energetics of trace-element partitioning between olivine and silicate melts: Implications for the nature of mineral/melt partitioning

[J]. Chemical Geology, 1994, 117(1/4): 57-71.

Horn I , Foley S F , Jackson S E , et al .

Experimentally determined partitioning of high field strength-and selected transition elements between spinel and basaltic melt

[J]. Chemical Geology, 1994, 117(1/4): 193-218.

Li Chusi , Ripley E M , Mathez E A .

The effect of S on the partitioning of Ni between olivine and silicate melt in MORB

[J]. Chemical Geology, 2003, 201(3): 295-306.

Righter K , Leeman W P , Hervig R L .

Partitioning of Ni, Co and V between spinel-structured oxides and silicate melts: Importance of spinel composition

[J]. Chemical Geology, 2006, 227(1): 1-25.

Laubier M , Grove T L , Langmuir C H .

Trace element mineral/melt partitioning for basaltic and basaltic andesitic melts: An experimental and laser ICP-MS study with application to the oxidation state of mantle source regions

[J]. Earth and Planetary Science Letters, 2014, 392(5): 265-278.

Simkin T , Smith J V .

Minor-element distribution in olivine

[J]. Journal of Geology, 1970, 78(3): 304-325.

[本文引用: 1]

Li Shibin , Song Xieyan , Hu Ruizhong , et al .

Magmatic evolution processes of SegmentⅡ in the Jinchuan Ore-bearing intrusion,Gansu Province

[J].Geoscience, 2007, 23(10): 2 553- 2 560.

[本文引用: 1]

李士彬,宋谢炎,胡瑞忠, .

甘肃金川Ⅱ号岩体岩相学特征及分离结晶过程探讨

[J]. 岩石学报, 2007, 23(10): 2 553-2 560.

[本文引用: 1]

Righter K , Leeman W P , Hervig R L .

Partitioning of Ni, Co and V between spinel-structured oxides and silicate melts: Importance of spinel composition

[J]. Chemical Geology, 2006, 227(1): 1-25.

[本文引用: 2]

Canil D .

Vanadium in peridotites, mantle redox and tectonic environments: Archean to present

[J]. Earth and Planetary Science Letters, 2002, 195(1): 75-90.

[本文引用: 1]

Papike J J , Karner J M , Shearer C K .

Comparative planetary mineralogy: Valence state partitioning of Cr, Fe, Ti, and V among crystallographic sites in olivine, pyroxene, and spinel from planetary basalts

[J]. American Mineralogist, 2005, 90(2/3): 277-290.

[本文引用: 1]

Shearer C K , Mckay G , Papike J J , et al .

Valence state partitioning of vanadium between olivine-liquid: Estimates of the oxygen fugacity of Y980459 and application to other olivine-phyric martian basalts

[J]. American Mineralogist, 2006, 91(10): 1 657-1 663.

[本文引用: 1]

Barnes S J , Godel B , Gürer D , et al .

Sulfide-olivine Fe-Ni exchange and the origin of anomalously Ni rich magmatic sulfides

[J]. Economic Geology, 2013, 108(8): 1 971-1 992.

[本文引用: 1]

Li Chusi , Zhang Zhengwei , Li Wenyuan , et al .

Geochronology, petrology and Hf-S isotope geochemistry of the newly-discovered Xiarihamu magmatic Ni-Cu sulfide deposit in the Qinghai-Tibet plateau, western China

[J]. Lithos, 2015, 216/217(2): 224-240.

[本文引用: 1]

Barnes S J , Tang Zhongli .

Chrome spinels from the Jinchuan Ni-Cu sulfide deposit, Gansu Province, People's Republic of China

[J]. Economic Geology, 1999, 94(3): 343-356.

[本文引用: 1]

Barnes S J , Kunilov V Y .

Spinels and Mg ilmenites from the Noril’sk 1 and Talnakh intrusions and ither mafic rocks of the Siberian flood basalt province

[J]. Economic Geology, 2000, 95(8): 1 701-1 717.

[本文引用: 1]

Huang Ke , Zhu Mingtian , Zhang Lianchang , et al .

LA-ICP-MS analysis of magnetite and application in genesis of mineral deposit

[J]. Advances in Earth Science, 2017, 32(3): 262-275.

[本文引用: 1]

黄柯, 朱明天, 张连昌, .

磁铁矿LA-ICP-MS分析在矿床成因研究中的应用

[J]. 地球科学进展, 2017, 32(3): 262-275.

[本文引用: 1]

Rajamani V .

Partition of Fe, Co, Ni and Cu between sulfide liquid and basaltic melts and the composition of Ni-Cu sulfide deposits

[J]. Economic Geology, 1978, 73(6): 1 520-1 528.

[本文引用: 1]

Laubier M , Grove T L , Langmuir C H .

Trace element mineral/melt partitioning for basaltic and basaltic andesitic melts: An experimental and laser ICP-MS study with application to the oxidation state of mantle source regions

[J]. Earth and Planetary Science Letters, 2014, 392(5): 265-278.

[本文引用: 1]

Li Chusi , Naldrett A J .

Geology and petrology of the Voisey's Bay intrusion: Reaction of olivine with sulfide and silicate liquids

[J]. Lithos, 1999, 47(1): 1-31.

[本文引用: 1]

Mao Yajin , Qin Kezhang , Barnes S J , et al .

A revised oxygen barometry in sulfide-saturated magmas and application to the Permian magmatic Ni-Cu deposits in the southern Central Asian Orogenic Belt

[J]. Mineralium Deposita, 2018, 53(6): 731-755.

[本文引用: 1]

Xue Shengchao , Qin Kezhang , Tang Dongmei , et al .

Olivine and Cr-spinel constraints on the petrogenesis, mineralization and source characteristics of nickel-mineralized Poshi intrusion, NE Tarim

[J]. Chinese Journal of Geology, 2016, 51(4): 1 181-1 203.

[本文引用: 1]

薛胜超, 秦克章, 唐冬梅 .

塔里木东北缘坡十Ni矿化侵入体中橄榄石和铬尖晶石对成岩成矿及源区特征的约束

[J]. 地质科学, 2016, 51(4): 1 181-1 203.

[本文引用: 1]

Xie Wei , Song Xieyan , Deng Yufeng , et al .

Geology and olivine geochenistry of the Heishan Ni-Cu-(PGE) sulfide deposit, Gansu, NW China

[J]. Acta Petrologica Sinica, 2013, 29(10): 3 487-3 502.

[本文引用: 2]

颉炜, 宋谢炎, 邓宇峰 .

甘肃黑山铜镍硫化物含矿岩体的地质特征及橄榄石成因探讨

[J]. 岩石学报, 2013, 29(10): 3 487-3 502.

[本文引用: 2]

Deng Yufeng , Song Xieyan , Hollings P , et al .

Lithological and geochemical constraints on the magma conduit systems of the Huangshan Ni-Cu sulfide deposit, NW China

[J]. Mineralium Deposita, 2016, 52(6): 1-18.

[本文引用: 1]

Matzen A K , Wood B J , Baker M B , et al .

The roles of pyroxenite and peridotite in the mantle sources of oceanic basalts

[J]. Nature Geoscience, 2017, 10(7): 32-45.

[本文引用: 2]

Sobolev A V , Krivolutskaya N A , Kuzmin D V .

Petrology of the parental melts and mantle sources of Siberian trap magmatism

[J]. Petrology, 2009, 17(3): 253-286.

[本文引用: 1]

Jin Shengkai , Zhang Zhaochong , Cheng Zhuiguo , et al .

Compositions of olivine from the Wajilitag mafic-ultramafic intrusion of the Permian Tarim Large Igneous Province, NW China: Insights into recycled pyroxenite in a peridotite mantle source

[J]. Journal of Asian Earth Sciences, 2019, 171: 9-19.

[本文引用: 1]

Heinonen J S , Fusswinkel T .

High Ni and low Mn/Fe in olivine phenocrysts of the Karoo meimechites do not reflect pyroxenitic mantle sources

[J]. Chemical Geology, 2017, 467: 131-142.

[本文引用: 1]

Condie K C .

Chemical composition and evolution of the upper continental crust: Contrasting results from surface samples and shales

[J]. Chemical Geology, 1993, 104(1/4): 1-37.

[本文引用: 1]

/