Zircon U–Pb ages and geochemistry of granite porphyries in the Yangla Cu deposit, SW China: constraints on petrogenesis and tectonic evolution of the Jinshajiang suture belt
Zircon U–Pb ages and geochemistry of granite porphyries in the Yangla Cu deposit, SW China: constraints on petrogenesis and tectonic evolution of the Jinshajiang suture belt
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羊拉铜矿床花岗斑岩锆石U-Pb年龄和地球化学：对金沙江缝合带岩石成因和构造演化的制约
DOI：
10.1155/2020/8852277
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发表时间：
2020
期刊：
影响因子：
1.7
通讯作者：
Zhilong Huang
中科院分区：
文献类型：
--
作者：
Bo Li;Xinfu Wang;Lijuan Du;Zuopeng Xiang;Guo Tang;Zhilong Huang
滇西北金沙江缝合带位于特提斯构造域的东部，以其大规模分布的侏罗纪-三叠纪花岗岩类而闻名，其成因与古特提斯洋的演化和多金属成矿作用有关。采用激光烧蚀电感耦合等离子体质谱法和锆石U-Pb年龄法对三个花岗斑岩样品进行了年代学和地球化学分析，分别获得213 ± 15、198.4 ± 8.6和195.3 ± 6.4Ma的年龄。这些年龄比花岗闪长岩的侵位年龄（208-239 Ma）年轻，表明羊拉矿区的岩浆活动可能持续了约44 Ma。这些GP富含大离子亲石元素如Rb、Ba、Th、U、K和La，但缺乏高场强元素如Ta、Nb、Ce、Zr、Hf和Ti。成矿元素富集程度为Cu > Pb > Zn。稀土元素的总含量在50.41- 127.27ppm之间，轻稀土/重稀土比值在4.46-10.54之间。GP富含LREE，LREE和HREE之间存在高度分化。δEu（EuN/Eu 3+）和δCe（CeN/Ce 3+）值分别为0.53-0.86和0.79-0.98，指示弱和弱负异常。GP的地球化学特征表明，这些岩体是在碰撞晚期或碰撞后构造环境中形成的钙碱性系列中的轻微变铝质至过铝质S型花岗岩。岩浆的三组分混合，包括上地壳、下地壳和地幔物质，以及随后的部分熔融，可能是在<5 kbar的超热低压环境中产生这些GP的原因。
Located in the eastern part of the Tethyan tectonic domain, the Jinshajiang Suture Belt (JSB), northwestern Yunnan, China, is notable for its large‐scale distribution of Jurassic to Triassic granitoids that are genetically related to the evolution of the Paleo‐Tethys Ocean and polymetallic mineralization. In this study, geochronological and geochemical analyses were conducted on three samples of these granite porphyries (GPs) using laser ablation inductively coupled plasma mass spectrometry and zircon U–Pb aging to reveal ages of 213 ± 15, 198.4 ± 8.6, and 195.3 ± 6.4Ma, respectively. These ages are younger than the emplacement ages of the granodiorites, at 208–239 Ma, suggesting that magmatic activities in the Yangla mining district likely continued for ~44 Ma. These GPs are rich in large‐ion lithophile elements such as Rb, Ba, Th, U, K, and La but are deficient in high field strength elements such as Ta, Nb, Ce, Zr, Hf, and Ti. Significant Pb enrichment and P depletion were noted, as were varying degrees of metallogenic element enrichment in the order of Cu > Pb > Zn. The total content of rare earth elements (ΣREEs) of the GPs is in the range of 50.41–127.27 ppm and the LREE/HREE ratio is in the rage of 4.46–10.54. The GPs are rich in LREEs, with a high degree of differentiation noted between the LREEs and HREEs. TheδEu (EuN/Eu∗) andδCe (CeN/Ce∗) values, at 0.53–0.86 and 0.79–0.98, indicate weak and slightly weak negative anomalies, respectively. The geochemical characteristics of the GPs indicate that these bodies are slightly metaluminous to peraluminous S‐type granites in a calc–alkaline series that formed in a late‐collisional or postcollisional tectonic setting. Three‐component mixing of magmas including those of upper crust, lower crust, and mantle materials in addition to subsequent partial melting could have been responsible for the generation of these GPs in an epithermal low‐pressure setting at <5 kbar.