内蒙古温都尔庙—白乃庙地区古板块会聚带的成矿作用及金属矿带的初步划分

    MINERALIZATION AND PRELIMINARY DIVISION OF METALLOGENIC BELTS IN A PALEOPLATE CONVERGENCE ZONE IN THE WENDURMIAO-BAINEIMIAO AREA, INNER MONGOLIA

    • 摘要: 西起内蒙古百灵庙,东经温都尔庙到镶黄旗、东苏旗一带(北纬42°~43°范围内)。是习称的地台一地槽分界带或过渡带,赋存有铁、铜、金、铬、钨、锡和稀土等矿产资源。近年来,新的矿种和矿点又不断被发现。矿化带呈近东西向展布,与古生代早中期这一带的大地构造背景有密切的成因关系。一、古板块会聚带构造模式概述我们的工作区主要集中于东经112°~114°,北纬42°~43°之间(图1)。这一带的古洋壳残片的构造和消减杂岩系列可证实古板块会聚带的存在。笔者在另文里叙述了该带的

       

      Abstract: The author considers that there had existed a mechanism of subduction of oceanic crust of the Paleo-Asiatic ocean system beneath the lithosphere of the Sino-Korean craton since the Paleozoic in the Wendunmiao area. During the period from the Late Silurian to Early Devonian, owing to the change of the pole of subduction, oceanic crust was obducted onto transitional crust in retrograde motion and meanwhile the consumed complex was pushed onto the earth’s surface. Specific iron, chromite, copper and gold mineralizations occur in the ophiolite suite and island-arc rock series and form metallogenic belts. The belts are regularly distributcd; from oceanic crust towards the continent, belts of Fe--Cr--Cu (Au) --Au are arranged successively. They respectively contain a series of ore deposits or occurrences. Iron mineralization is represented by the Si-Fe formation on slpes of the mid-ocean ridge. Iron substances were derived from a byssal tholeiite by strong spilitization. That is to say, iron mineralization is mainly genetically related to green schist of the ophiolite suite. On the other hand, chrome minealiza- tion is related to emplaced serpentinized ultrabasic rocks of the first associa- tion of the ophiolite suite. Molybdenum-poor porphyry-copper deposits and gold deposits and their ore zones were formed in Baineimio in the immature island are occurring on simatic oceanic crust. Andesite-basalt and granodiorite-porphyry sills are host rocks of porphyry iron deposits and have close genetic relations with these deposits. The thermal system of a high-temperature axis resulting from subduction at the island arc and back-arc basin continued until the Hercynian (and even until the early Yanshanian). Therefore, synchroneity, lag and continuity might all exist with regard to the relations of magmatism and mineralization to various processes produced during plate convergence. Under the guidance of the plate-tectonic theory, the traditional ideas about metallogenesis and directions in ore prospecting will change by great extent. Metallogenesis at both sides of the line of latitude 42°N should be related to various processes produced during plate convergence so as to promote the study and exploitation of the great metallogenic belts.

       

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