Geochronology and geochemistry of granitoids related to the giant Dahutang tungsten deposit, middle Yangtze River region, China: Implications for petrogenesis, geodynamic setting, and mineralization
Geochronology and geochemistry of granitoids related to the giant Dahutang tungsten deposit, middle Yangtze River region, China: Implications for petrogenesis, geodynamic setting, and mineralization
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DOI：
10.1016/j.gr.2014.07.005
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发表时间：
2015-09
影响因子：
6.1
通讯作者：
Zhihao Mao;Jiajun Liu;J. Mao;Jun Deng;Feng Zhang;Xuyang Meng;Bikang Xiong;Xin-kui Xiang;
中科院分区：
文献类型：
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作者：
Zhihao Mao;Jiajun Liu;J. Mao;Jun Deng;Feng Zhang;Xuyang Meng;Bikang Xiong;Xin-kui Xiang;
扬子克拉通北部长江中游地区的斑岩和夕卡岩矿床，钨资源总量约30万吨(Mt)，是世界上最重要的钨矿区之一。大湖塘斑岩钨矿床是最大的矿床之一，储量为100万吨。铀铅分析得出斑状黑云母花岗岩的年龄为147.4±0.58 Ma-148.3±21.9 Ma，细粒花岗岩为144.7±0.47 Ma-146.1 Ma±60.64 Ma，花岗斑岩为143.0±0.76 Ma-143.1 Ma±11.2 Ma，与野外观测结果一致。地球化学数据表明，这三类花岗岩具有富Rb、Pb、U，亏损Ba、Nb、P、Ti的特征，具有过铝熔体的特征[摩尔Al_2O_3/(CaO)~(2+)Na_2O~(2+)+K_2O]~(1.1)。花岗岩中P_2O_5含量为0.13~0.37%，与SiO_2呈正相关，属S型侵入岩。斑状黑云母花岗岩的初始87Sr/86Sr为0.721~0.731，ε为5.06~−；细粒花岗岩为0.7196~0.7289，−为6.29~6.74；花岗斑岩为0.7153~0.7365，−为5.09~7.64。花岗岩的球粒陨石标准化稀土元素(REE)配分模式具有轻稀土富集和Eu强烈负异常的特征，表明它们来自元古代泥质和砂砾岩基地层，并经历了强烈的斜长石分离结晶。大湖塘S式岩浆活动和钨成矿作用的年龄约为150~140Ma，与长江中下游含铜、金、钼、铁斑岩和矽卡岩矿床有关的I型岩浆作用的年龄一致。我们认为，侏罗纪末期至白垩纪早期的花岗岩类和矿石形成于俯冲的Izanagi板块撕裂期间，导致软流圈上涌，从而导致地幔-地壳相互作用。S型花岗岩类及相关的W矿系是元古界地壳重熔的产物，而I型花岗岩类及相关矿石则是俯冲板块部分熔融的产物。
Porphyry and skarn deposits in the middle Yangtze Valley within the Northern Yangtze Craton have a combined tungsten resource of ~ 3 million tonnes (Mt) and represent one of the most important tungsten regions in the world. The Dahutang porphyry tungsten deposit, with reserves of > 1 Mt, is one of the largest deposits. Uranium–Pb analyses for the ore-related granitoids yield ages of 147.4 ± 0.58 Ma–148.3 ± 1.9 Ma for porphyritic biotite granite, 144.7 ± 0.47 Ma–146.1 ± 0.64 Ma for fine-grained granite, and 143.0 ± 0.76 Ma–143.1 ± 1.2 Ma for granite porphyry, a progressive youngling of ages that is consistent with field observations. Geochemical data show that the three types of granite are characterized by enrichments in Rb, Pb, and U, and depletion in Ba, Nb, P, and Ti, with ASI [molar Al2O3/(CaO + Na2O + K2O)] > 1.1 that is characteristic of a peraluminous melt. The P2O5contents of the granites are 0.13–0.37% and have a positive correlation with SiO2, and they are thus S-type intrusions. They exhibit initial87Sr/86Sr of 0.721 to 0.731 and εNd(t) of − 5.06 to − 7.99 for porphyritic biotite granite, 0.7196 to 0.7289 and − 6.29 to − 6.74 for fine-grained granite, and 0.7153 to 0.7365 and − 5.09 to − 7.64 for granite porphyry. Chondrite-normalized rare earth element (REE) patterns for the granites are characterized by enrichment in the light REE and a strong negative Eu anomaly, indicating that they were derived from the Proterozoic pelitic and psammitic basement strata and experienced strong fractional crystallization of plagioclase. Our ca. 150–140 Ma age for the Dahutang S-type magmatism and W mineralization is identical to that of the I-type magmatism related to Cu–Au–Mo–Fe-bearing porphyry and skarn deposits along the middle to lower Yangtze River Valley. We propose that the latest Jurassic to earliest Cretaceous granitoids and ores formed during a tearing of the subducting Izanagi slab, which caused the upwelling of asthenosphere and resulting mantle–crust interaction. The S-type granitoids and related W ore systems resulted from the re-melting of the Proterozoic crust, whereas the I-type granitic rocks and related ores are attributed to the partial melting of the subducted slab.