Geological, geochronological, geochemical, and Sr–Nd–O–Hf isotopic constraints on origins of intrusions associated with the Baishan porphyry Mo deposit in eastern Tianshan, NW China
Geological, geochronological, geochemical, and Sr–Nd–O–Hf isotopic constraints on origins of intrusions associated with the Baishan porphyry Mo deposit in eastern Tianshan, NW China
复制标题
DOI：
10.1007/s00126-016-0646-z
复制
发表时间：
2016-03
影响因子：
4.8
通讯作者：
Yin‐Hong Wang;C. Xue;Jiajun Liu;Fangfang Zhang
中科院分区：
文献类型：
--
作者：
Yin‐Hong Wang;C. Xue;Jiajun Liu;Fangfang Zhang
白山斑岩钼存款（0.72 Mt; 0.06% Mo）位于新疆东天山造山带内部。该存款包括15个矿体，与二长花岗岩和花岗斑岩股票和结构控制的大致东西向断层。二长花岗岩和花岗斑岩的二次离子质谱（西姆斯）锆石U-Pb年龄为228 ± 2 ~ 227 ± 2 Ma，与榴辉岩Re-Os模式年龄226 ± 3 ~ 228 ± 3 Ma一致。三叠纪二长花岗岩和花岗斑岩属高钾钙碱性系列，具高SiO2、Al 2 O3和低MgO、TiO 2、P2 O 5的特征，具Eu负异常（δEu = 0.55-0.91）。蚀变最小的二长花岗岩和花岗斑岩的εNd（t）值在+1.6 ~+3.6之间，（87 Sr/86 Sr）比值在0.7035 ~ 0.7071之间，表明它们来自下地壳。锆石O-Hf同位素原位二次离子西姆斯和激光烧蚀多接收电感耦合等离子体质谱分析LA-MC-ICP-MS结果表明，某二长花岗岩样品中锆石的δ 18 O和εHf（t）值分别为6.1 ~ 7.3 ‰和+8.0 ~+11.7，花岗斑岩样品中锆石的变化范围分别为6.2 ~ 6.9 ‰和+7.3 ~+11.2 ‰。地球化学和同位素数据表明，白山花岗岩的原始岩浆可能来自下地壳的部分熔融，其中含有地幔成分。白山钼存款和花岗岩侵位最可能与造山后岩石圈伸展和岩浆底侵作用有关。一个伸展事件，加上热幔源熔体的上升，引发了下地壳的部分熔融，以及提供金属（钼）。
The Baishan porphyry Mo deposit (0.72 Mt; 0.06 % Mo) is located in the interior of the eastern Tianshan orogenic belt in Xinjiang, NW China. The deposit comprises 15 orebodies that are associated with monzogranite and granite porphyry stocks and are structurally controlled by roughly EW-trending faults. Secondary ion mass spectrometry (SIMS) zircon U–Pb dating of the monzogranite and granite porphyry yielded the Middle Triassic age (228 ± 2 to 227 ± 2 Ma), which coincide with the molybdenite Re–Os model ages ranging from 226 ± 3 to 228 ± 3 Ma. The Triassic monzogranite and granite porphyry belong to high-K calc-alkaline series and are characterized by high SiO2and Al2O3and low MgO, TiO2, and P2O5concentrations, with negative Eu anomalies (δEu = 0.55–0.91). The least-altered monzogranite and granite porphyry yield uniformεNd(t) values from +1.6 to +3.6, and wide (87Sr/86Sr)iratios ranging between 0.7035 and 0.7071, indicating that they were derived from the lower crust. In situ O–Hf isotopic analyses on zircon using SIMS and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) indicate that the δ18O andεHf(t) values of zircon from a monzogranite sample vary from 6.1 to 7.3 ‰ and +8.0 to +11.7, respectively, whereas zircon from a granite porphyry sample vary from 6.2 to 6.9 ‰ and +7.3 to +11.2, respectively. The geochemical and isotopic data imply that the primary magmas of the Baishan granite were likely derived from partial melts from the lower crust involving some mantle components. The Baishan Mo deposit and granitic emplacement were proposed to be most likely related to post-orogenic lithospheric extension and magmatic underplating. An extensional event coupled with the rising of hot mantle-derived melts triggered partial melting of the lower crust, as well as provided metals (Mo).