银根-额济纳旗盆地苏红图坳陷H井锆石LA-ICP-MSU-Pb定年及其地质意义

苏红图坳陷位于银根-额济纳旗盆地的北部，该区勘探程度较低，地层格架尚不明确，特别是对于深部火山岩所在地层年代存在很大争议。研究区火山岩发育，火山活动对油气成藏影响较大，但火山活动期次尚不明确。通过对研究区一口钻井系统取样，样品涵盖浅部的沉积岩和深部的火山岩，开展样品的锆石U-Pb年代学研究，以期为以上问题的解决提供证据。结果表明:①无论是碎屑锆石还是火山岩锆石，除了少数古老年龄的锆石属于变质成因，其余年轻的锆石均属于岩浆成因锆石。每个样品均有3组年龄，且不同样品的锆石年龄组有所重叠。②深部火山岩的形成年代为早白垩世，该年龄对火山岩所在的深部地层年代具有很好的约束作用。③年轻的岩浆成因锆石年龄可划分为4组，分别是132.6±0.7 Ma、237.9±3.2 Ma、（255.4±6.2~263.7±2.2）Ma和（314.1±2.3~328.5）Ma，代表了研究区晚古生代以来的4期火山活动，对应的年代分别为早白垩世、中三叠世、晚二叠世和早石炭世，其中以晚二叠世火山活动最为广泛和强烈。本次研究成果为研究区地层划分、火山岩预测等提供了有力的依据。

U-PbAge of Zircon and Its Geological Significance in Suhongtu Depression,Yingen-Ejinaqi Basin

Suhongtu depression is in the northern part of the Yingen-Ejinaqi basin, stratigraphic framework here is still unclear because of the low degree of exploration, especially, there is a big controversy on the location of the deep stratum with volcanic rock. The volcanic rocks in the study area are very developed, volcanic activity has larger influence on hydrocarbon accumulation, but activity times of volcanic remains unclear. In this study, systematic sampling has been carried out from a drilling well in Suhongtu depression. The samples were both shallow sedimentary rocks and deep volcanic rocks. Then, the U-Pb geochronology of the samples was studied, expecting it will provide evidence for the solution of the above problem. The results showed that:①Whether detrital zircon or volcanic zircons, except that a few old age zircons belonged to metamorphic origin, and the rest younger zircons belonged to the magmatic origin. Zircon ages of each sample were concentrated in three groups, and some of the age groups overlapped in different samples. ②The formation age of deep volcanic rocks was early Cretaceous, it provided some restraints on the formation with deep volcanic rocks. ③The age of all the younger magmatic zircons for every samples can be divided into four age groups:132.6±0.7 Ma, 237.9±3.2 Ma, 255.4±6.2 Ma~263.7±2.2 Ma and 314.1±2.3 Ma~328.5 Ma. The four age groups represented four volcanic activities since late Paleozoic, and the corresponding age were early Carboniferous, late Permian, middle Triassic and early Cretaceous, respectively, among these the most widely and strongly volcanic activity was late Permian. The research provided a strong basis for stratigraphic division and volcanic prediction in the study area.