The Study On The Material Composition,Tectonic Deformation And Metallogenic Characteristics Of Ophiolitic Tectonic Mélange Belt In Annan Dam Area,Altyn

Ophiolitic tectonic mélange belt is the most representative geological entity in the non Smith stratigraphy of orogenic belt.The formation of generally experienced oceanic lithosphere subduction,collision,uplifting and strike-slipping of the continents.So that the material composition,structural deformation and mineralization processes are very complex.It is an important material carriers to reveal orogenic process,the palaeo-plate structure evoluation process.In this paper,based on analyzing the domestic and foreign ophiolitic tectonic mélange belt on the latest research,combining with field geological investigation and indoor comprehensive analysis,makes an analysis of Annan dam ophiolitic tectonic mélange belt of the eastern Altyn.It also provides the basis for evolution and the metallogenic regularity summary and evaluation of mineral resources.Through the study of material compositions,distributional characteristics on the time and space spatial,ages,geochemical properties,tectonic environment,deformation sequence,metallogenic characteristics,the change and preservation of the ore body in Annan dam ophiolitic tectonic mélange belt,we can reach the following conclusions:(1)The material composition of Annan dam area are mainly composed of 5 kinds of tectonic blocks which are granitic gneiss rocks block(exotic block),meta-basic volcano rocks block(non ophiolite composition),ophiolite rocks block,meta-intermediate-acidic volcano rocks block,sedimentary rocks and volcano sedimentary rocks block.And the corresponding shearing groundmasses.(2)The tectonic blocks(weak deformation domain)and shearing matrix(strong deformation zone)showed alternant distribution.Blocks are arounded by shearing matrix and showing the structure of network-structural;(3)Isotope chronology shows the ages: granitic gneiss rocks formation age(787±19Ma~776±24Ma),(exotic block),meta-basic volcano rocks(non ophiolite composition)formation age(524±2Ma),ophiolite rocks formation age(520.4±1.2Ma),meta-intermediate-acidic volcano rocks formation age(475±3Ma~450±2Ma),sedimentary rocks and volcano sedimentary rocks block formation age(during Cambrian Ordovician and Late Carboniferous Early Permian(Upper Permian basin sedimentary rocks))in the Annan dam Ophiolitic tectonic mélange belt;(4)The corresponding forming tectonic environment based on geochemistry characteristics of 5 types of tectonic block are as followed: Volcano arc-continental plate environment,ocean island,ocean ridge,island arc and back arc basin environment.This spatial distribution implied an obvious polar: A subduction from north to south;(5)According to the structural features and its tectonic superposition replacement relation of the tectonic mélange belt,divided into 3 kinds of tectonic associations--subduction stage,collision stage and uplifting stage.And making an analysis of mechanical property of tectonic mélange belt,we innovatively developed “opposite thrust” structural styles of ophiolitic tectonic mélange belt.(6)Based on the analysis of metallogenic characteristics of the Annan dam ophiolitic tectonic mélange belt,we have studied mining geology,orebody characteristics,ore bodies and ore geochemistry,the formation age and the genetic types of the hematite(magnetite)body;(7)Based on regional geological characteristics,combining with 4 stages of tectonic evolution of the ophiolitic tectonic mélange belt,Studied the formation,changes and preservation processof the Annan dam of hematite(magnetite);(8)Studing the occurrences positions and occurrences states of Annan dam hematite(magnetite)lenticular ore bodies(weak deformation domain)and schisteous ores(strong deformation zone),provides the basis for the mineral resources assessment and geological exploration engineerings.