Proterozoic deformation in the northwest of the Archean Yilgarn Craton, Western Australia
Proterozoic deformation in the northwest of the Archean Yilgarn Craton, Western Australia
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西澳大利亚太古宙 Yilgarn 克拉通西北部的元古代变形
DOI：
10.1016/j.precamres.2007.10.004
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发表时间：
2008
影响因子：
3.8
通讯作者：
S. Wilde
中科院分区：
文献类型：
--
作者：
C. Spaggiari;J;S. Wilde
伊尔加恩克拉通西北部的纳瑞尔地体包含了澳大利亚最古老的地壳。杰克山绿岩带位于纳瑞尔地体的南部，切割它的构造和围岩已经用40Ar/39Ar技术测定了年代。结果表明，1830~1780 Ma的摩羯座造山运动与东向、右旋、走滑的剪切作用有关，1760~1740 Ma之间进一步变形和/或冷却。这些结果证实了元古代伊尔格伦克拉通西北部处于克拉通内环境的大变形。元古代构造被解释为从Narryer地体向南延伸到Youanmi地体(Murchison域)的北部，包括Yalgar断层，以前被解释为Narryer地体和Youanmi地体之间的边界。地体混杂作用早于两个地体中2660 Ma左右的花岗岩侵位，而雅加尔断裂目前的表现必然代表了一种更年轻的、重新改造的、后混杂的结构，可能受构造边界的控制。然而，新的航磁和重力图像并没有显示出耶尔加断层的东部是一个主要结构。它的特征更类似于一系列从东到东-东北方向的断层，这些断层被解释为元古界。这表明，雅加尔断裂的这一部分可能不是地体边界，可能不超过元古界。~(40)Ar/~(39)Ar测年还表明，在约1172 Ma时有较年轻的、强度较小的变形和/或冷却事件。
The Narryer Terrane within the northwestern Yilgarn Craton contains the oldest crust in Australia. The Jack Hills greenstone belt is located within the southern part of the Narryer Terrane, and structures cutting it and surrounding rocks have been dated using the40Ar/39Ar technique. The results show that east-trending, dextral, transpressive shearing was related to the 1830–1780Ma Capricorn Orogeny, followed by further deformation and/or cooling between c. 1760 and 1740Ma. These results confirm that major deformation has affected the northwestern part of the Yilgarn Craton in an intracratonic setting during the Proterozoic. Proterozoic structures have been interpreted to extend south beyond the Narryer Terrane into the northern part of the Youanmi Terrane (Murchison Domain), and include the Yalgar Fault, previously interpreted as the boundary between the Narryer and Youanmi Terranes. Terrane amalgamation pre-dated the emplacement of c. 2660Ma granites in both terranes, and the current expression of the Yalgar Fault must represent a younger, reworked, post-amalgamation structure, possibly controlled by the tectonic boundary. However, new aeromagnetic and gravity imagery does not show the eastern part of the Yalgar Fault as a major structure. Its signature is more akin to a series of east- to east-northeast trending faults that are interpreted to be Proterozoic in age. This suggests that this part of the Yalgar Fault may not be a terrane boundary, and is possibly no older than Proterozoic. The40Ar/39Ar dating also shows a younger, less intense deformation and/or cooling event at c. 1172 Ma.