Tectonostratigraphic and geochronologic constraints on evolution of the northeast Paleotethys from the Songpan-Ganzi complex, central China
Tectonostratigraphic and geochronologic constraints on evolution of the northeast Paleotethys from the Songpan-Ganzi complex, central China
复制标题
DOI：
10.1016/j.tecto.2007.11.053
复制
发表时间：
2008-04
期刊：
影响因子：
2.9
通讯作者：
A. Weislogel
中科院分区：
文献类型：
--
作者：
A. Weislogel
中国中部松潘-甘孜杂岩（SGC）的中、晚三叠世深水沉积物约有2.0× 106 km 3的碎屑物质堆积在古特提斯最东北的分支中。对现有资料的回顾表明，这些浊积岩的地层和岩石学特征在空间和时间上都有显著的变化。这些变化被用来划分为不同的沉积中心：东北部沉积中心（SGC-NE），东中部沉积中心（SGC-EC）和西北部沉积中心（SGC-NW）。松潘-甘孜杂岩的SGC-NE带和SGC-EC带的浊积岩地层与华北和华南地块的碰撞有关，而SGC-NW带的浊积岩地层可能与昆仑变形带的演化关系更密切。为验证松潘-甘孜地层格架的有效性及其构造地层演化解释，对松潘-甘孜地区5个长英质侵入火成岩样品、2个邻近义敦弧杂岩的长英质深成岩样品、和一个火山岩样品与中三叠世浊积岩的SGC使用灵敏的高分辨率离子微探针-反向几何（SHRIMP-RG）。这些数据表明，主要是晚三叠世（~214-211 Ma）的长英质岩浆活动在SGC，与一些迹象表明，岩浆活动开始早在中三叠世（220 Ma）。义敦岛弧杂岩的锆石年龄支持中晚三叠世岩浆活动发生在225-215 Ma之间，早于SGC的变形，表明SGC的变形与SGC基底向西南俯冲到义敦岛弧之下无关。在SGC-EC的两个样品中发现的继承性新元古代（880-740 Ma）锆石年龄表明，在地壳增厚和岩浆成因过程中，它们要么继承了周围SGC浊积岩地层的锆石晶体，要么可能与华南基底有关。
The Middle to Late Triassic deep-water deposits that form the Songpan-Ganzi complex (SGC) of central China comprise an estimated ~2.0×106km3of detrital material that accumulated in the northeasternmost branch of the Paleotethys. A review of existing data demonstrates significant spatial and temporal variations in the stratigraphic and petrologic character of these turbidites. These variations are used to divide the complex into different depocenters: a northeastern depocenter (SGC-NE), a eastern–central depocenter (SGC-EC) and a northwestern depocenter (SGC-NW). Turbidite strata of the SGC-NE and SGC-EC zones of the Songpan-Ganzi complex are linked to the collision of the North China and South China blocks, whereas turbidite strata of the SGC-NW area are likely to be more closely affiliated with evolution of the Kunlun deformation belt. To test the validity of the Songpan-Ganzi stratigraphic framework and interpretations of its tectonostratigraphic evolution, sixty-eight U–Pb zircon ages were determined from five samples of felsic intrusive igneous rock, two samples from felsic plutonic rock of the adjacent Yidun arc complex, and one sample of volcanic rock interbedded with Middle Triassic turbidites of the SGC using the Sensitive High Resolution Ion Microprobe-Reverse Geometry (SHRIMP-RG). Together these data indicate primarily Late Triassic (~214–211 Ma) felsic magmatism in the SGC, with some indication of magmatic activity beginning as early as Middle Triassic (220 Ma). Zircon ages from the Yidun arc complex support Middle–Late Triassic magmatism from 225–215 Ma, prior to deformation of the SGC, suggesting deformation of the SGC was not related to subduction of the SGC substrate southwestward beneath the Yidun arc. Inherited Neoproterozoic (880–740 Ma) zircon ages found in two samples from the SGC-EC indicate either inheritance of zircon crystals from the surrounding SGC turbidite strata or possibly involvement of South China basement during crustal thickening and magma genesis.