A geological map of the Early Cretaceous lower crust in Shanxi Province has been compiled based on granite data,which has added vitrinite reflectance data and recompiled the geological map of the Early Cretaceous lower crust in Shanxi Province.Many new insights have been obtained through comparison,which indicates that vitrinite reflectance is a very useful dataset for lower crustal mapping.Vitrinite reflectance can record the maximum temperature reached after its formation and is one of the widely used and reliable methods for maturity measurement in coalfield and petroleum geology departments.The vitrinite reflectance method is also very useful in petrology and mineral deposit studies.Therefore,it is possible to infer the presence,distribution,and scale of concealed rock mass in deeper layers,as well as the presence and distribution of mantle upwelling at the base of the lower crust based on vitrinite reflectance data.A new method for mineral exploration involves using vitrinite reflectance distribution to locate concealed rock masses and subsequently prospecting for mineral deposits based on these features.This paper infers that concealed rock mass may exist in the deeper layers of several areas where Ro＞3.0％based on the distribution of vitrinite reflectance in Shanxi Province.Among these,the concealed rock mass in Qixian has already been confirmed through drilling verification.There are many coal mines in Shanxi Province,and all anthracite distribution areas are favorable regions for locating concealed rock mass.The paper also revises the geological map of the Early Cretaceous lower crust in Shanxi Province based on vitrinite reflectance data,pointing out that the deeper layers in the central and southern parts of Shanxi Province are extensive regions of Mesozoic(mainly Early Cretaceous)granite distribution,which were also areas of mantle upwelling during the Early Cretaceous.It is inferred based on stratigraphic and granite data that the northern part of Shanxi Province(north of Datong)represents a region with normal crustal thickness,while the southern part represents a region of crustal thickening(part of the eastern China plateau).The southern part is a mantle upwelling region,while the northern part shows no signs of mantle upwelling.Therefore,the lower crust in the southern part is a high-temperature eclogite facies region,while the lower crust in the northern part is a low-temperature eclogite facies region.The lower crust is a fluid-bearing eclogite facies region in areas with surface mineral deposits.The lower crust in the central and western parts of Shanxi Province may represent a transitional zone between eclogite facies and granulite facies,suggesting that the eastern China plateau in Shanxi Province may exhibit a gradual westward subsidence trend.
关键词
山西省/镜质组反射率/无烟煤/下地壳地质图/隐伏岩体/高原/早白垩世
Key words
Shanxi Province/vitrinite reflectance/anthracite/lower crust geological map/concealed rock mass/plateau/Early Cretaceous
维普
万方数据