大陆裂谷盆地钾盐矿床特征与成矿作用
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引用本文:刘成林.2013.大陆裂谷盆地钾盐矿床特征与成矿作用[J].地球学报,34(5):515-527.
DOI:10.3975/cagsb.2013.05.02
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刘成林 中国地质科学院矿产资源研究所, 国土资源部成矿作用与资源评价重点实验室 liuchengl@263.net 
基金项目:国家“973”计划项目(编号: 2011CB403007);国家自然科学基金项目(编号: 41202059)
中文摘要:全球板块运动对表生成钾控制明显, 即从古生代到中新生代, 从巨型稳定克拉通陆表海盆成钾, 到中生代特提斯海域海盆成钾, 再到新生代的大陆裂谷盆地成钾, 地球表生成钾模式发生了重大转变; 成钾物质来源从海水补给为主, 转变为非海相(以火山活动带来深部物质和陆表水)与海相混合型, 甚至以非海相深部物质补给为主。全球裂谷成钾时期正好处于Pangea超大陆解体及新特提斯洋闭合时期, 成钾的裂谷型蒸发岩盆地也主要位于这两个构造域内, 这些进一步表明裂谷成钾是地球板块构造运动演化历史的必然结果。典型的裂谷盆地钾盐矿床有: 大西洋裂谷形成初期沉积的刚果(布)白垩纪钾盐矿、欧洲大陆莱茵地堑第三纪钾盐矿、非洲大陆埃塞俄比亚达纳基尔钾盐矿等; 同时, 还有众多裂谷盆地蕴藏有富钾卤水矿, 如死海裂谷富钾卤水、东非大裂谷一些富钾盐湖、美国加州索尔顿海高温富钾热卤以及中国江陵凹陷富钾热卤等。这些钾盐矿的共同特点是: 盆地内发育火山岩和温热泉, 具有深源补给的明显特征; 尽管裂谷盆地规模一般很小, 但形成的钾盐规模最大可达数十亿吨。总结世界大陆裂谷盆地钾盐矿床特征、物质来源与成矿作用, 提出了大陆裂谷型小盆地成钾模式。其裂谷成钾过程可分解为“二个阶段”, 第一阶段, 地表盐湖-太阳能作用, 第二阶段, 埋藏-岩浆热能作用; 成钾作用有三个, 即蒸发沉积作用、沉积后淋滤改造作用和埋藏变质改造作用。中国中新生代裂谷型盆地比较发育, 进一步研究大陆裂谷盆地成钾作用, 可以为此类盆地找钾提供理论依据和指导。
中文关键词:大陆裂谷  火山作用  蒸发岩  钾盐  富钾卤水
 
Characteristics and Formation of Potash Deposits in Continental Rift Basins: A Review
Abstract:Global plate movements obviously control the formation of supergene potash deposits. The formation of potash deposits underwent several distinct changes from the Paleozoic period to the Mesozoic-Cenozoic periods. That is, the potash deposits were formed mainly in the epicontinental basins in the Paleozoic stable giant cratons, in the Tethyan ocean basins in Mesozoic, and in continental rift basins in Cenozoic period. The sources of potash deposits were firstly mainly derived from sea water in the Palaeozoic period, then changed into the mixed sources comprising non-marine sources composed of deep materials brought by volcanic activities, earth’s surface water and sea water. Non-marine deep sources were even the primary sources especially in continental rift basins. The periods of potash formation of the continental rifting basins just corresponded with the splitting of Pangea super-large continent and the closing of Neo-Tethys, and these evaporite basins were located in the two tectonic regions. So the potash formation of the rifting basins was probably the inevitable result of the Earth’s crust tectonic movement. There are some typical potash deposits that occurred in rift basins, such as the Cretaceous potash deposit in Republic of Congo that occurred at the beginning of the Atlantic rifting, the Tertiary potash deposit that occurred in the Rhine graben, and the Dana Gil potash deposit that occurred in Ethiopia. Moreover, there are plenty of potassium-rich brine deposits, such as the Dead Sea, some salt lakes in East African Rift Valley, the Salton Sea in the USA, and China’s Jiangling depression. These brine potash deposits are characterized by volcanic activities and hot springs, which are typical for the deep source supplement. Although the sizes of these rift basins are relatively small, there exist a great number of potash resources up to billions of tons in reserves of KCl. In this paper, the author give a review of the characteristics of potash deposits, sources and mineralization in the continental rift basins, and propose a potash-forming model for small-sized rift basins. Potash formation of the continental rifting might be divided into two stages, i.e., the solar-pond stage in which salt lakes under going evaporation, and the stage of underground geothermal action. Three kinds of mechanisms of the potash formation include evaporation, dissolution of the former crystallized salts, and reformation of the brine. Based on the understanding of the potash-forming model in rifts, the authors gained some successes in the exploration of potash deposits in Jiangling rift depression. It is thus held that further study of the mineralization of potash-forming in continental rift basins, some of which are well developed in China, can provide a theoretical basis and guidance for potash exploration in China’s rift basins.
keywords:continental rift  volcanism  evaporite  potash deposit  potassium-rich brines
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