Petrogenesis of the Piqiang ma?c-ultrama?c layered intrusion and associated Fe-Ti-V oxide deposit in Tarim Large Igneous Province, NW China
Petrogenesis of the Piqiang ma?c-ultrama?c layered intrusion and associated Fe-Ti-V oxide deposit in Tarim Large Igneous Province, NW China
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塔里木火成岩省皮羌镁铁质-超镁铁质层状岩体及伴生铁钛钒氧化物矿床的岩石成因
DOI：
10.1080/00206814.2019.1584867
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发表时间：
2019-12-12
影响因子：
2.6
通讯作者：
Tao, Jihua
中科院分区：
文献类型：
--
作者：
Cao, Jun;Wang, Xuan;Tao, Jihua
皮强侵入体是塔里木大火成岩省二叠纪塔里木大型铁钛钒氧化物矿床的两个重要的层状侵入体之一。侵入岩主要由边缘带的辉长岩、斜长岩和少量含斜长石的斜辉岩组成。铁钛氧化物矿石呈层状和透镜状分布在辉长岩中，呈块状分布。SHRIMP锆石U-Pb来自皮强侵入体的辉长岩和周围花岗岩墙的花岗岩，其年龄约为270 Ma。岩石地球化学特征为轻稀土元素(LREE)和大离子亲石元素(LILE)富含，高强元素(HFSE)中等亏损，锶-钕-氢同位素组成范围有限。层状单元相似的矿物学、矿物组成和微量元素特征表明，所有岩石都是同岩浆的。母岩浆富铁钛，类似于与皮强岩体有关的最原始的辉绿岩墙。塔里木地幔热柱的部分熔融与俯冲交代岩石圈地幔源区的参与，最好地解释了皮强侵入体母岩浆的地球化学和岩石成因。我们认为，岩石圈地幔源区可能受到俯冲相关物质的交代作用和该源区的交代富集作用，这可能与南天山洋板在早、中古生代向南俯冲过程中的大洋沉积物循环有关。结晶沉淀和机械分选是皮强侵入体中块状铁钛氧化物矿石形成的主要过程。成矿的中心是富铁钛母岩浆漫长的分异历史和后来来自围岩的外部H2O加入缓慢冷却的岩浆室的共同作用。
The Piqiang intrusion is one of the two important ma?c-ultrama?c layered intrusions that host giant Fe-Ti-V oxide deposits in the Permian Tarim Large Igneous Province, NW China. The intrusion mainly consists of gabbro, anorthosite and minor plagioclase-bearing clinopyroxenite in the marginal zone. Disseminated to massive Fe-Ti oxide ores occur as layers and lenses within the gabbro. SHRIMP zircon U-Pb results from both a gabbro from the Piqiang intrusion and a granite from the surrounding granitic dyke yield ages of ~270 Ma. Geochemically, the Piqiang silicate rocks are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), moderately depleted in high ?eld strength elements (HFSE), and have a limited range of Sr-Nd-Hf isotopic compositions. The similar mineralogy, mineral compositions, and trace element characteristics of the layered units suggest that all the rocks are co-magmatic. The parental magma is Fe-Ti-rich and is akin to the most primitive diabasic dyke which is associated with the Piqiang intrusion. Partial melting of the Tarim mantle plume with involvement of a subduction-metasomatized lithospheric mantle source best explains the geochemistry and petrogenesis of the parental magmas of the Piqiang intrusion. We propose that the lithospheric mantle source may have been metasomatized by subduction-related materials and the metasomatic enrichment of this source region which may be correlated with oceanic sediment recycling during southward subduction of the South Tianshan oceanic slab during the Early-Middle Paleozoic. Crystal settling and mechanical sorting is the predominant process responsible for the formation of the massive Fe-Ti oxide ores in the Piqiang intrusion. Central to ore formation is a combination of the protracted differentiation history of a Fe-Ti-enriched parental magma and the later addition of external H2O from the country rocks to the slowly cooling magma chamber.