柴达木东北部晚石炭世盆山格局研究

Late Carboniferous mountain-basin framework of Northeastern Qaidam area

关键词:  柴达木东北部  晚石炭世  盆山格局  地球化学  碎屑锆石

Key words:  Northeastern Qaidam area  Late Carboniferous  mountain-basin framework  geochemistry  detrital zircon

摘要:

根据地球化学、碎屑锆石测试资料和大地构造学理论,对石灰沟剖面克鲁克组碎屑岩物源区性质及构造属性进行研究。结果表明:柴达木东北部地区晚石炭世盆地类型为被动大陆边缘盆地,物源区岩石组合以中酸性岩浆岩为主,缺少基性物质的加入,也不存在明显的沉积再旋回;克鲁克组碎屑岩物源区主要由古老基底组成,但包含一定加里东期物质,柴北缘构造带依旧是碎屑物质来源之一;晚石炭世海侵及盆地沉降受北侧宗务隆晚古生代裂陷海槽控制,碎屑物质来源于南侧柴北缘加里东造山带,呈“南山-北海”的盆山格局,盆地内部充填海相沉积建造;柴北缘古生代造山带剥蚀开始于约430 Ma前,存在时间下限不晚于晚石炭世,早期主要发生岛弧岩浆岩的剥蚀,晚期则主要发生古老基底的剥蚀。

Abstract:

The characteristics and structural attribute of the provenance of Keluke Formation clastic rocks from Shihuigou profile were studied according to the geochemistry, test data of detrital zircon and geotectonic theory. It is found that the type of late Carboniferous basin in northeastern Qaidam margin is passive margin basin. And the intermediate-acid magmatic rocks of the rock assemblage are dominant in the provenance. The basic-intermediate acidic rocks are absent, and there is no obvious sedimentary cycle. Provenance of Keluke Formation is mainly composed of antique basement. However, it also involves a certain amount of Caledonian period material, indicating the north Qaidam tectonic belt is still one of the detrital material sources. The Late Carboniferous transgression and basin subsidence are controlled by the Zongwulong late Paleozoic aulacogen in the north. And the detrital material came from the north Qaidam Caledonian orogenic belt, showing the basin-orogen pattern of "southern mountain-northern sea". The internal basin is filled with marine sedimentary. The denudation history of North Qaidam Paleozoic orogen started from ca. 430 Ma, and its existence is no later than Late Carboniferous. The arc magmatic rocks are erased in the earlier stage and the erosion of antique basement happens in the later period.