DOLOMITIZATION OF LOWER ORDOVICIAN IN EASTERN SECTOR OF NORTH TARIM REGION

Guo Jianhua; Sheng Zhaoguo; Li Jianming

doi:10.11743/ogg19940105

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DOLOMITIZATION OF LOWER ORDOVICIAN IN EASTERN SECTOR OF NORTH TARIM REGION
Vol. 15, Issue 1, Pages: 51-59(1994)
Online First：25 March 1994，

Published：1994
DOI： 10.11743/ogg19940105
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DOI：

Guo Jianhua, Sheng Zhaoguo, Li Jianming. DOLOMITIZATION OF LOWER ORDOVICIAN IN EASTERN SECTOR OF NORTH TARIM REGION[J]. 1994, 15(1): 51-59. DOI： 10.11743/ogg19940105.

摘要

塔北隆起东段下奥陶统中的白云石化岩石类型可划分为四类:(1)层状藻纹层白云岩

(2)条带状白云质灰岩

(3)残余内碎屑角砾状含灰质白云岩-白云岩及(4)班块状含白云质灰岩-灰质白云岩.组成以上四种岩石类型的白云石

主要为半自形-它形粒状白云石、自形菱面体细晶白云石及自形菱面体细粉晶白云石.通过对白云石的矿物学、阴极发光及地球化学特征的研究

认为区内白云石化作用均是在有淡水参与的作用下进行的

划分出两期白云石化作用

并相应地提出两个白云石化模式:(1)近地表浅埋藏淡水稀释白云石化及(2)深埋藏压实淡水-孔隙卤水混合白云石化.

Abstract

Four types of dolomitized rocks have been found in the eastern sector of North Tarim uplift: 1. bedding stromatolite dolostone; 2. ribboned dolomitic limestone;3. remaining intraclastic breccioid calciferous dolomite-dolomite and 4. lumpy dolomitic limestone-calcic dolostone. The dolomites forming the above mentioned rocks are mainly a. subhedral-allotriomorphic granular dolomite; b. euhedral rhombohedron fine crystalline dolomite; c. euhedral rhombohedron fine silt-sized crystalline dolomite. The features of their mineralogy

cathodoluminescence and geochemistry show that the dolomitization in the area are all resulted from the mixing of fresh water and sea water. In consideration of the basic features of the sediments and texture

two periods of dolomitization and consequently two models of dolomitization are proposed in this paper: 1. shallow-buried fresh water dilution in near surface and 2. deep-buried fresh watre-pore bittern mixing.