Late Mesozoic magmatism from the Daye region, eastern China: U–Pb ages, petrogenesis, and geodynamic implications
Late Mesozoic magmatism from the Daye region, eastern China: U–Pb ages, petrogenesis, and geodynamic implications
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DOI：
10.1007/s00410-008-0341-x
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发表时间：
2009-03
影响因子：
3.5
通讯作者：
Jian-wei Li;Xin-Fu Zhao;Mei‐Fu Zhou;Changqian Ma;Z. S. Souza;P. Vasconcelos
中科院分区：
文献类型：
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作者：
Jian-wei Li;Xin-Fu Zhao;Mei‐Fu Zhou;Changqian Ma;Z. S. Souza;P. Vasconcelos
晚中生代闪长和石英闪长岩体广泛分布于扬子克拉通东部、中国东部的大冶地区。对其中的大部分进行了详细的地质年代学、地球化学和锶-钕同位素研究，以期对广泛岩浆活动的年龄、成因和地球动力学控制提供全面的认识。SHRIMP和LA-ICPMS锆石U-Pb定年结果表明，该岩体侵位时代为晚侏罗世(约152 Ma)至早白垩世(约132 Ma)，其后为127~121 Ma的岩墙侵位和130~113 Ma的火山活动。闪长岩和石英闪长岩均为钠铝质高钾钙碱性闪长岩，具有强烈分馏、近平行的稀土配分模式，无明显的Eu异常。岩石富含高度不相容元素和大离子亲石元素，但亏损高场强元素。闪长岩和石英闪长岩样品具有相似的锶-钕同位素组成，与扬子克拉通东部早白垩世玄武岩和镁铁质侵入岩一致。地球化学和同位素数据与地球化学模拟结果相结合，为深成岩提供了丰富的地幔来源。石英闪长岩具有与埃达克岩相似的地球化学特征，如高Al_2O_3(15~19ppm)、高Sr(630~2080ppm)、高Na2O(>；3.5wt.%)、负Nb-Ta异常、低Y(7~19ppm)、低Yb(0.5~1.8ppm)、低Sc(5~15ppm)，以及由此产生的高Sr/Y(45-200)和La/Yb(31-63)比值。埃达克质石英闪长岩的成因可以用来自地幔闪长岩浆的角闪石、斜长石、钾长石、磁铁矿和磷灰石等堆积物的低压壳内分离结晶来解释。与大冶地区大致同时代的地幔岩浆活动也广泛存在于扬子克拉通东部其他地区，反映了晚中生代岩石圈地幔的大规模熔融作用。这种大规模的岩浆活动很可能是由与中国大陆东部之下的岩石圈地幔减薄有关的岩石圈伸展驱动的。
Late Mesozoic dioritic and quartz dioritic plutons are widespread in the Daye region, eastern Yangtze craton, eastern China. Detailed geochronological, geochemical, and Sr–Nd isotopic studies have been undertaken for most of these plutons, in an attempt to provide a comprehensive understanding in the age, genesis and geodynamical control of the extensive magmatism. SHRIMP and LA-ICP-MS zircon U–Pb dating indicate that the plutons were emplaced in the range of latest Jurassic (ca. 152 Ma) to early Cretaceous (ca. 132 Ma), which was followed by dyke emplacement between 127 and 121 Ma and volcanism during the 130–113 Ma interval. Both diorites and quartz diorites are sodic, metaluminous, high-K calc-alkaline, and characterized by strongly fractionated, sub-parallel REE patterns without obvious Eu anomalies. The rocks are enriched in highly incompatible elements and large ion lithophile elements, but depleted in high field strength elements. Samples of diorite and quartz diorite have similar Sr–Nd isotopic compositions that are consistent with the early Cretaceous basalts and mafic intrusions throughout the eastern Yangtze craton. The geochemical and isotopic data, together with results of geochemical modeling, indicate an enriched mantle source for the plutonic rocks. The quartz diorites have geochemical signatures resembling adakites, such as high Al2O3(15–19 wt.%), Sr (630–2,080 ppm), Na2O (>3.5 wt.%), negative Nb–Ta anomalies, low Y (7–19 ppm), Yb (0.5–1.8 ppm), Sc (5–15 ppm), and resultant high Sr/Y (45–200) and La/Yb (31–63) ratios. Genesis of the adakitic quartz diorites is best explained in terms of low-pressure intracrustal fractional crystallization of cumulates consisting of hornblende, plagioclase, K-feldspar, magnetite, and apatite from mantle-derived dioritic magmas. Mantle-derived magmatism broadly coeval with that of the Daye region also is widespread in other regions of the eastern Yangtze craton, reflecting large-scale melting of the lithospheric mantle during the Late Mesozoic. The large-scale magmatism was most likely driven by lithospheric extension associated with thinning of lithospheric mantle beneath the eastern China continent.