下刚果盆地构造活动对钾盐成矿及后期改造的约束

发布时间：2018-04-05 01:13

本文选题：下刚果盆地　切入点：钾盐矿床　出处：《中国地质大学(北京)》2017年博士论文

【摘要】：我国相对缺乏钾盐资源,是我国“走出去”战略的目标矿种之一。在新一轮的海外钾盐勘查开发的大潮中,下刚果滨海盐盆地钾盐成为研究的重点和热点。下刚果滨海盐盆地位于西非被动大陆边缘裂谷盆地群,地处西部非洲中段,呈北西-南东向条带状展布,与海岸线平行,在白垩系地层广泛发育了巨厚的蒸发岩沉积。其中在下刚果和加蓬滨海盆地沉积了厚层具有工业价值的钾盐矿物。为厘清大西洋型裂谷成钾盆地的构造演化控制钾盐矿床的发育及赋存规律,本文重点研究盆地构造活动对钾盐成矿及其后期改造作用,丰富完善典型钾盐成矿模式,探索构造活动对钾盐成矿及其后期改造的约束机制,为进一步的矿产勘查和矿山开发提供有益的参考。下刚果盐盆地属于典型的裂谷成钾盆地,在前人研究的基础之上,本文利用物、化、遥、钻等勘查资料对研究区构造活动与钾盐成矿的关系进行了细致研究,结合区域大地构造背景、构造-沉积演化历史、蒸发岩沉积序列等,确定了研究区的构造样式:因被动大陆边缘的掀斜作用,盆地呈东北方向高,西南方向低,向海缓倾斜的特征,盆地沉积的几何中心在研究区西南方向,确定了矿区北北东向为主应力场变化特征,盆地构造环境总体稳定。多种地质资料表明,构造活动作为核心要素在下刚果盐盆地成矿模式中占有非常重要的地位,并且贯穿钾盐成矿的始终。在构造-物源-气候三大关键因素耦合作用机制的基础上,系统建立区内地层系统,详细分析了沉积韵律与环境,利用盆地平衡剖面恢复手段,结合构造分析,将研究区构造活动在成矿演化划分为三个主要阶段:成矿准备阶段;蒸发沉积成矿阶段;成矿后改造阶段。利用研究区蒸发岩地层有机夹层富含的铼锇同位素,首次获得了研究区准确的蒸发岩沉积年代:78.7±1.1至96±7Ma。基于以上工作,总结成矿盆地演化规律,阐明矿床成因,提出下刚果盐盆地的钾盐成矿的构造作用机制。探索研究区构造控矿机制能够丰富、完善前人提出的裂谷成钾模型,增进盆地成矿规律的研究,使得前后工作相互验证,相互补充,由此建立区域钾盐矿床沉积的空间模型,为今后定向找钾工作提供必要的理论支持。
[Abstract]:The relative lack of potash resources in China is one of the target minerals of our country's "going out" strategy.In a new round of overseas potash exploration and development, potash salt in the Lower Congo coastal salt basin has become the focus and hot spot.The Lower Congo coastal salt basin is located in the West African passive continental margin rift basin group, is located in the middle part of West Africa, and distributes in a north-southwest striped direction, parallel to the coastline. In the Cretaceous strata, extremely thick evaporite deposits are widely developed.Among them, potash minerals of industrial value have been deposited in the coastal basins of Lower Congo and Gabon.In order to clarify the development and occurrence of potash deposits controlled by the tectonic evolution of the Atlantic rift basin, this paper focuses on the basin tectonic activities for potash mineralization and its later transformation, and enriches the typical potash metallogenic models.This paper explores the constraint mechanism of tectonic activity on potash mineralization and its later transformation, which provides a useful reference for further mineral exploration and mining development.Bas-Congo salt basin is a typical rift basin. On the basis of previous studies, this paper makes a detailed study of the relationship between tectonic activity and potash mineralization in the study area by using the exploration data such as material, chemistry, telecontrol and drilling.Combined with the regional tectonic background, the history of tectonic-sedimentary evolution and the sedimentary sequence of evaporite, the structural patterns of the study area are determined: due to the tilting of passive continental margin, the basin is high in northeast direction and low in southwest direction.The characteristics of gently tilting to the sea and the geometric center of the basin deposition are in the southwest of the study area. The variation characteristics of the main stress field in the NNE direction of the mining area are determined, and the tectonic environment of the basin is generally stable.A variety of geological data show that tectonic activity as the core element plays a very important role in the ore-forming model of Bas-Congo salt basin and runs through the process of potash mineralization.On the basis of coupling mechanism of three key factors of tectonics, provenance and climate, the stratigraphic system in the area is systematically established, the sedimentary rhythm and environment are analyzed in detail, and the basin balanced section restoration method is used to combine structural analysis.The tectonic activities in the study area are divided into three main stages: metallogenic preparation stage, evaporative depositional metallogenic stage and post-metallogenic transformation stage.Using the rich rhenium and osmium isotopes of organic intercalation in evaporite strata in the study area, the accurate sedimentary age of evaporite is obtained for the first time: 78.7 卤1.1 to 96 卤7 Ma.Based on the above work, the evolution law of ore-forming basin is summarized, the genesis of ore deposit is clarified, and the tectonic mechanism of potash mineralization in Lower Congo Salt Basin is put forward.Exploring the ore-controlling mechanism of structure in the study area can enrich, perfect the kalium model put forward by predecessors, promote the study of metallogenic law in the basin, make the work before and after mutually verify and complement each other, and establish the spatial model of regional potash deposit deposit.To provide the necessary theoretical support for the future directed looking for potassium.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P619.211

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