Study Of The Precambrian Supracrustal Rocks In Alatengaobao Region Of Aixa Youqi, Inner Mongolia

There is a set of Early-Precambrian intermediate and advanced levelmetamorphic series distributed in the study area of Alatanaobao Region-YabulaiMountain belts.Which the predecessors had collectively referred to as the Alax group,and the age were archean era. This study divided the metamorphic series into theoriginal rock of the volcanic-sedimentary rocks and the original metamorphosedgneissic of rock for the metamorphic plutonic intrusive rocks, and furtherly divide thePrecambrian metamorphosed supracrustal rocks in this area into De’erhetong rockgroup and Zuzongmaodao rock group, according to the characteristics of the rockassociation.This paper based on detailed field observations, analyzed the Precambrianmetamorphosed supracrustal rock by petrochemical data, points out the rockassociation characteristics, petrological characteristics and petrochemicalcharacteristics, completes its protolith restoration.We choose characteristic mineral forelectronic probe test analysis, and we choose appropriate mineral thermometer andmineral temperature, pressure plan to calculate temperature and pressure.Througth restortating protolith obtained that the Hawala rock group is mainly aset of sedimentary of metamorphic volcanic rocks and part of clastic deposit; thedownside of De’erhetong rock group is mainly clastic deposit and part of sedimentaryof metamorphic volcanic rocks,and the upside are mainly volcanic rock-clastic depositand carbonate sediment. The downside of Zuzongmaodao rock group is mainlyargillaceous-arenaceous-volcanic sediment,and the upside of which is mainlycarbonate-argillaceous-arenaceous sediment,part of volcanic sediment.They formedin activitie continent margin arc and in shore environment.Used garnet-biotitethermograph and GASP thermobarometer we calculated that the pressure ofmetamorphism in basement is about O.68GPa,650℃.It undergos medium pressureand medium-pyro metamorphism,and the metamorphic facies belongs to greenschistfacies-amphibolite facies.A few isotopic dates which we collected suggest that the Precambrian metamorphosed supracrustal rock formed in Mesoproterozoic.This is extraordinarydifferent from which the predecessors difined as the Alax group.So we doubt thetectonic setting of which the predecessors used know.Based on contrasting analysiswe think that the tectonic setting of study area is far different from North ChinaCraton metamorphic block.