东天山阿其克库都克断裂西段土古土布拉克组锆石SHRIMP U-Pb测年

SHRIMP U-Pb dating of zircons from the Tugutu Bulak Formation in the western segment of the Aqqikkuduk fault in the East Tianshan, Xinjiang, China

1∶5万区域地质调查发现,在中天山隆起带北部黑龙峰一带的阿其克库都克断裂带及其两侧,出露一套火山碎屑岩夹正常沉积岩,含有海百合茎和腕足化石碎片。对其中含砾岩屑砂岩中花岗闪长斑岩砾石的锆石进行SHRIMPU-Pb定年,获得206Pb/238U加权平均年龄为314Ma±4.2Ma(n=9,MSWD=1.8),表明该套地层不老于314Ma±4.2Ma,应归为晚石炭世土古土布拉克组。这一发现表明,至少自石炭纪以来,阿其克库都克断裂在该区不具有构造分区的意义。

A suite of pyroclastic rocks with normal sedimentary rocks, containing fragments of brachiopods and crinoids, is found along the Aqqikkuduk fault zone and its both sides in the Heilongfeng area m the northern part of the Central uplift by 1：50000 regional geological survey. SHRIMP U-Pb dating of zircons from granodiorite porphyry gravels in a conglomeratic lithic sandstone sample from this suite of rocks yields a weighted mean age of 314.0±4.2 Ma （n=9, MSWD=1.8）. This age indicates that the suite of rocks is not older than 314.0±4.2 Ma and so should be assigned to the Late Carboniferous Tugutu Bulak Formation. This finding suggests that the Aqqikkuduk fault has no significance for tectonic division at lest since the Carboniferous.