Discussion Of Sedimentary Environment And Age Of The Gongyanghe Group In Longling Area, Yunnan Province

Gongyanghe Group distributed between Luxi-Ruili fracture and Nujiang fracture,north-south trending, is one of the important non-ferrous and precious metalmineralization belt. Research on the age,formation attribution,lithofaciespaleogeography evolution and other scientific issues of Gongyanghe Group in theregion indicate the direction of precious metals prospecting work, as well as lay thefoundation for further study the Structural properties and evolution of metamorphismand deformation of the Gaoligongshan in Pan-African. In this thesis, as the researchobject to Gongyanghe Group in Longling area, Integrated use of stratigraphy,paleontology, sedimentology, geochemistry, structural geology theory and techniques,System to carry out the study of petrology and petrochemistry of Gongyanghe Group,first gained a high-precision dating data, to provide a reliable basis for chronology todivision and constraints of Gongyanghe Group, on this basis, launched a study ofsedimentary facies and lithofacies paleogeography evolution of GongyangheGroup,has made the following understanding:First, Gongyanghe Group was divided into four sections based on thecombination of rock and rock: at the bottom of Gongyanghe Group is not foundbecause of intrusived by Ordovician adamellite, mainly mica schist with thinmetasandstone; Gongyanghe Group Sec mainly sericite phyllite with quartz schist;three segments of Gongyanghe Group is mainly of slate sericite-kaolinite clay rockswith chlorite rocks with tremolite rocks and mica slate; Gongyanghe Group of four ismainly metamorphic sandstone, phyllite and feldspathic lithic sandstone, no top.Gongyanghe Group have different sedimentary enviroments in different places,inManghai area for slope-basin facies transition sedimentary environment, the slopefacies sedimentary environment as the main body; there were delta-shore-shallowbasin depositional environment in Jiufang area; and in Zhen’an-Longxin area itperformanced shore-shelf-basin depositional environment.Select the Gongyanghe Group in Longling area as the main object of study,combined with geological background, focuses on the following research:1)stratigraphic division of Gongyanghe Group;2) analysis the depositional environmentof Gongyanghe Group;3)discussing the era of Gongyanghe Group.We divided theGongyanghe Group sedimentary facies of Longling area into3types of sedimentaryfacies include shoreside facies, shelf facies and basin facies, based on section and the test analysis of the samples.In this study, we identified the strata sequence which have several layers ofmetamorphic basic volcano rock in the Bangmai Section in Longling county. Wesuggested that its original rock was basalt which was formed in intra-continentaltension environment and was probably relate to extension after the Pan-Africanorogenic period. We for the first time have got the U-Pb age (499.2±2.1Ma) ofmetamorphic basic volcano rocks’ zircon and provided a reliable chronology basisfor the division of the Gongyanghe Group and restriction of age. The foundation isvery important for the tectonic characteristics and history of the deformationmetamorphic belt of Gaoligong Hill.