Platinum-group element geochemistry of the layered intrusions in the Emeishan large igneous province, SW China: Implications for the principal controls on magmatic sulfide immiscibility
Platinum-group element geochemistry of the layered intrusions in the Emeishan large igneous province, SW China: Implications for the principal controls on magmatic sulfide immiscibility
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峨眉山大火成岩省层状岩体铂族元素地球化学：对岩浆硫化物不混溶性主控的启示
DOI：
10.2475/04.2017.03
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发表时间：
2017-04
影响因子：
2.9
通讯作者：
Hu Jun-Hao
中科院分区：
文献类型：
--
作者：
She Yu-Wei;Song Xie-Yan;Chen Lie-Meng;Yu Song-Yue;Zhu Xiang-Kun;Yi Jun-Nian;Hu Jun-Hao
人们普遍认为，外部硫通过地壳污染的掺入是硫化物不混溶的重要触发因素，硫化物不混溶产生了Ni-Cu-(PGE)硫化物矿化，但也可能存在其他控制硫化物不混溶的因素。峨眉山大火成岩省晚二叠世攀枝花、白马、红歌、新街、太河等层状侵入体赋存丰富的铁钛氧化物矿床，其硫化物成矿以亚经济成矿为主。例如，新街侵入体下部有少量薄的富pge矿层，而其他ELIP层状侵入体不含任何Ni-Cu硫化物矿化，pge贫（0.01-1 ppb）。与成因相关的峨眉山高钛玄武岩相比，攀枝花、白云、太和和红阁侵入岩的PGE亏缺程度和Cu/Pd比值升高（高达3.2×106）表明其母岩岩浆由于早期硫化物的去除而发生了PGE亏缺。攀枝花、白马和太和岩体的Sr-Nd同位素组成表明，地壳污染不明显，硫化物饱和度不可能主要由地壳硫输入产生。熔体模拟表明，深部岩浆房中铬铁矿、橄榄石和斜辉石的广泛分馏可能导致了原生岩浆的早期硫化物饱和。攀枝花、白马、红歌和太河铁钛氧化物层中硫化物含量较高，表明第二阶段硫化物不混溶与铁钛氧化物广泛结晶密切相关。硫含量与总Fe2O3、V和TiO2呈正相关关系，表明Fe- ti氧化物（磁铁矿和钛铁矿）结晶可能通过大幅降低岩浆中Fe浓度和氧逸度触发了第二阶段硫化物饱和。新街铁钛氧化物贫岩受中等程度的地壳污染，可能导致硫化物在侵入体下部饱和富集。计算结果表明，新街富pge岩石具有较高的r因子（1000 ~ 10000），这是由于pge未枯竭岩浆与新补充的硫化物发生反应而使硫化物发生pge升级所致。攀枝花、白马和太河样品中PGE含量较高，表明深部早期硫化物液滴是在后期岩浆脉冲中被带入较浅岩浆房的。通过质量平衡计算得出的极高r因子表明，在岩浆管道系统的深部侵入体中有可能发现更多的PGE矿化。
It is widely accepted that the incorporation of external sulfur via crustal contamination is an important trigger for sulfide immiscibility that generates Ni-Cu-(PGE) sulfide mineralization, yet other controlling factors for sulfide immiscibility may also be present. The late Permian Panzhihua, Baima, Hongge, Xinjie and Taihe layered intrusions in the Emeishan Large Igneous Province (ELIP, SW China), are well-endowed with Fe-Ti oxide deposits, whereas their sulfide mineralization is mainly sub-economic. For example, the lower part of the Xinjie intrusion hosts a few thin PGE-rich ore layers, yet other ELIP layered intrusions do not contain any Ni-Cu sulfide mineralization and are PGE-depleted (0.01–1 ppb). Compared with the PGE-undepleted Emeishan high-Ti basalts that are genetically related to the intrusions, the extent of PGE depletion and elevated Cu/Pd ratios (up to 3.2×106) of the Panzhihua, Baima, Taihe and Hongge intrusions suggest PGE-depletion in their parental magmas due to early-stage sulfide removal. Sr-Nd isotopic compositions of the Panzhihua, Baima and Taihe intrusions suggest crustal contamination was insignificant and sulfide saturation produced mainly by crustal sulfur input was unlikely. MELTS modeling shows that extensive fractionation of chromite, olivine and clinopyroxene in deep-seated magma chambers may have induced early-stage sulfide saturation of the primary magmas. The relatively high sulfide contents in the Fe-Ti oxide layers at Panzhihua, Baima, Hongge and Taihe indicate a close relationship between the second-stage sulfide immiscibility and extensive Fe-Ti oxide crystallization. Positive correlations between sulfur and total Fe2O3, V and TiO2 suggest that Fe-Ti oxide (magnetite and ilmenite) crystallization may have triggered the second-stage sulfide saturation via sharply lowering the Fe concentration and oxygen fugacity of the magmas. Moderate degree of crustal contamination for the Xinjie Fe-Ti oxide-barren rocks may have induced sulfide saturation and accumulation at the lower part of the intrusion. Our calculations indicate that the Xinjie PGE-rich rocks have high R-factors (1000–10000), which are ascribed to PGE-upgrading of the sulfides via reaction with new replenishments of PGE-undepleted magmas. A few Panzhihua, Baima and Taihe samples that contain higher PGE concentrations suggest that the early-stage sulfide droplets at depths were entrained in later magma pulses delivered to shallower magma chambers. The very high R-factors determined by mass balance calculation, implies a good potential for discovering more PGE mineralization in the deep-seated intrusions of the magma plumbing system.
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影响因子：
1.8
作者：
Zhang Xiao
通讯作者：
Zhang Xiao
影响因子：
3.9
作者：
S. Klemme;D. Günther;K. Hametner;Stefan Prowatke;T. Zack
通讯作者：
S. Klemme;D. Günther;K. Hametner;Stefan Prowatke;T. Zack
影响因子：
5.8
作者：
A. J. Naldrett;E. Gasparrini;S. Barnes;G. Gruenewaldt;M. R. Sharpe
通讯作者：
A. J. Naldrett;E. Gasparrini;S. Barnes;G. Gruenewaldt;M. R. Sharpe
影响因子：
5.3
作者：
He, B;Xu, YG;Wang, Y
通讯作者：
Wang, Y
影响因子：
3.5
作者：
BARNES, SJ
通讯作者：
BARNES, SJ