Petrogenetic modeling of three mafic–ultramafic layered intrusions in the Emeishan large igneous province, SW China, based on isotopic and bulk chemical constraints
Petrogenetic modeling of three mafic–ultramafic layered intrusions in the Emeishan large igneous province, SW China, based on isotopic and bulk chemical constraints
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DOI：
10.1016/j.lithos.2009.04.023
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发表时间：
2009-12
期刊：
影响因子：
3.5
通讯作者：
Zhaochong Zhang;J. Mao;A. Saunders;Y. Ai;Ying Li;Li Zhao
中科院分区：
文献类型：
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作者：
Zhaochong Zhang;J. Mao;A. Saunders;Y. Ai;Ying Li;Li Zhao
峨眉山晚二叠世大火成岩省中部的镁铁质-超镁铁质层状岩体沿南北向断裂带排列沿着。本文报道了攀枝花辉长岩岩体、利马河橄榄岩岩体和新街橄榄岩、辉石岩岩体的Sr、Nd、Pb和O同位素组成。攀枝花辉长岩岩体主要含V-Ti-Fe矿石，利马河橄榄岩岩体主要含Cu-Ni-PGE矿石。攀枝花岩体演化程度较高，富Fe、Ti，而利马河含矿岩石富Mg，未矿化辉长闪长岩富Ca、Al，新街岩体的岩石学和地球化学特征介于这两个岩体之间。岩石学和地球化学研究表明，攀枝花岩体和新街岩体中存在大量的积云磁铁矿和钛铁矿。这改变了通常被认为在玄武岩系统中不相容的元素的比例（例如，La/Zr和La/Nb），因为高场强元素（Zr、Hf、Nb和Ta）显示出显著的配分到磁铁矿结构中[Klemme，S.，Günthe，D.，Hametner，K.，Prowatke，S.，Zack，T.，2006.微量元素在钛铁矿、钛尖晶石、铁铝尖晶石和硅酸盐熔体之间的分配与月球早期分化的关系。化学地质学234，251-263]。攀枝花岩体的母岩浆可能为铁苦橄岩。结合δ 18 O值<6‰，推测攀枝花岩体的形成可能是受到富Fe、Ti的岩石圈地幔源区的上侵地幔柱岩浆的混染。相反，负εNd（t）值（−0.6 ~ −4.13）、高δ 18 O值（>6‰）、放射成因Pb同位素组成以及高La/Nb和La/Ta比值表明，利马河岩体来自于受花岗质地壳物质混染的地幔柱岩浆。δ ~（18）O值（4.8-8.0‰）和Pb同位素比值表明，新街岩体可能是由地幔柱岩浆原位受基性地壳物质混染的结果。峨眉山陆内不同类型岩浆矿床的形成主要是由于岩浆来源不同。
Mafic–ultramafic layered intrusions align along a N–S trending fault zone in the central part of the late Permian Emeishan large igneous province, SW China. We present major and trace element and clinopyroxene Sr, Nd, Pb and O isotopic compositions of three representative mafic–ultramafic layered intrusions, the Panzhihua gabbro intrusion that hosts V–Ti–Fe ores, the Limahe peridotite intrusion that hosts Cu–Ni ores, and the Xinjie peridotite and pyroxenite intrusion that hosts both V–Ti–Fe and Cu–Ni–PGE ores. The Panzhihua intrusion is more evolved, and rich in Fe and Ti, whereas the Limahe ore-bearing rocks are rich in Mg, and the unmineralized gabbro-diorites are rich in Ca and Al. Both the petrology and geochemistry of the Xinjie intrusion are transitional between those of the two other intrusions. Petrography and geochemistry indicate that there is a large amount of cumulus magnetite and ilmenite in the Panzhihua and Xinjie intrusions. This has changed the ratios of elements normally considered incompatible in basaltic systems (e.g., La/Zr and La/Nb), because high field strength elements (Zr, Hf, Nb and Ta) show significant partitioning into the magnetite structure [Klemme, S., Günthe, D., Hametner, K., Prowatke, S., Zack, T., 2006. The partitioning of trace elements between ilmenite, ulvospinel, armalcolite and silicate melts with implications for the early differentiation of the moon. Chemical Geology 234, 251–263]. The parental magma of the Panzhihua intrusion is estimated to be ferropicrite. Thus, in combination with their low δ18O values (<6‰), we infer that the generation of the Panzhihua intrusion could be ascribed to ascending plume-derived magma contaminated by a Fe- and Ti-rich lithospheric mantle source. In contrast, negative εNd(t) values (−0.6 to −4.13), high δ18O values (>6‰), radiogenic Pb isotopic compositions, and high La/Nb and La/Ta ratios imply that the Limahe intrusion was derived from mantle-plume magmas contaminated by granitic crustal materials. The δ18O values (4.8–8.0‰) and Pb isotope ratios suggest that the Xinjie intrusion may result from plume-derived magmas variably contaminated by basic crustal materials in situ. The formation of the different types of the magmatic-ore deposits within the Emeishan LIP may be mainly attributed to their different sources.