Provenance, depositional setting, and crustal evolution of the Cathaysia Block, South China: Insights from detrital zircon U–Pb geochronology and geochemistry of clastic rocks
Provenance, depositional setting, and crustal evolution of the Cathaysia Block, South China: Insights from detrital zircon U–Pb geochronology and geochemistry of clastic rocks
复制标题
DOI：
10.1002/gj.3253
复制
发表时间：
2018-06
影响因子：
1.8
通讯作者：
C. Xiong;Hongde Chen;Y. Niu;A. Chen;Chenggong Zhang;Feng Li;Shenglin Xu;Shuai Yang
中科院分区：
文献类型：
--
作者：
C. Xiong;Hongde Chen;Y. Niu;A. Chen;Chenggong Zhang;Feng Li;Shenglin Xu;Shuai Yang
本文报道了华夏地区赣南晚新元古代至寒武纪碎屑沉积岩的碎屑锆石U-Pb年代学和块体岩石元素地球化学联合研究结果。这些碎屑岩具有中等化学蚀变指数(CIA)值73和高Th/U比值(>；3.8)的特征，表明源区处于中等风化状态。相对较高的成分变异性指数(ICV=0.62-1.30)表明物源成分以未成熟物质为主，缺乏富铝矿物。判别图上的块状岩石主量元素和微量元素系统与物源为古陆壳成因的长英质-中火成岩相一致。其地球化学特征也与沉积在被动大陆边缘或其附近的碎屑沉积岩相一致。碎屑岩的碎屑锆石U-Pb年龄记录了5个主要年龄组：2614-2376 Ma(峰值约2482 Ma)，1,953-1353 Ma，1000-900 Ma(峰值约958 Ma)，850-730 Ma(峰值约845 Ma和763 Ma)，685-571 Ma(峰值约635 Ma)。年龄数据提供了源区火成岩活动的记录：2,482 Ma的峰值与全球新太古代陆壳生长一致；1,953-1,353 Ma的年龄组与哥伦比亚超大陆的组装和解体时期相关；约958 Ma的显著峰值对应于与Rodinia的组装有关的常见热构造事件，850-730 Ma的组与Rodinia超大陆的解体相一致。约850 Ma的年龄指示了中国南部罗迪尼亚裂解的初始阶段。我们的数据还显示，670-530 Ma的年龄与与冈瓦那超大陆形成有关的泛非事件有很好的相关性，尽管在南海生物圈内还没有发现这一事件的直接地质证据。此外，复杂的锆石形态和全球范围内碎屑锆石U-Pb年龄谱的对比表明，华夏地块晚新元古代-寒武纪沉积岩可能来自具有晚太古代、格勒维利亚和泛非时代岩浆活动的外来源区，这些岩浆在华夏地块或邻区不露头，有待进一步勘探。
We report the results of a combined study of detrital zircon U–Pb geochronology and bulk‐rock elemental geochemistry on late Neoproterozoic to Cambrian clastic sedimentary rocks from South Jiangxi within Cathaysia. These clastic rocks are characterized by moderate chemical index of alteration (CIA) values of 73 and high Th/U ratios (>3.8), indicating moderate weathering of the source area. The relatively high index of compositional variability (ICV = 0.62–1.30) values indicates a source compositionally dominated by immature material that lacks alumina‐rich minerals. Bulk‐rock major and trace element systematics on discrimination diagrams are consistent with the source provenance being felsic‐intermediate igneous rocks of ancient continental crust origin. The geochemistry is also consistent with the clastic sedimentary rocks being deposited in a setting at or in the vicinity of passive continental margins. Detrital zircon U–Pb ages of the clastic rocks record five major age populations: 2,614–2,376 Ma (peak at ca. 2,482 Ma), 1,953–1,353 Ma, 1,000–900 Ma (peak at ca. 958 Ma), 850–730 Ma (peaks at ca. 845 and 763 Ma), and 685–571 Ma (peak at ca. 635 Ma). The age data provide a record of igneous activity in the source provenance: the 2,482 Ma peak is consistent with the global Neoarchean continental crust growth; the 1,953–1,353 Ma population correlates with the period of assembly and breakup of the Columbia supercontinent; the prominent peak at ca. 958 Ma corresponds to a common thermal–tectonic event associated with the assembly of Rodinia, and the 850–730 Ma population is consistent with the breakup of the Rodinia supercontinent. The ca. 850 Ma age is indicative of initial stage of Rodinia breakup in South China. Our data also reveal a 670–530 Ma population that correlates well with the Pan‐African event associated with the formation of the Gondwana supercontinent, although no direct geological evidence for this event has been found within the SCB. Moreover, complex zircon morphology and comparisons of detrital zircon U–Pb age spectra in a global context suggest the late Neoproterozoic–Cambrian sedimentary rocks in the Cathaysia Block must have sourced from an exotic source with magmatic activities of late Archean, Grenvillian, and Pan‐African ages, which do not outcrop in the Cathaysia Block or adjacent regions and need to be further explored.