| 华南晚古生代碳酸盐岩建造中层控铀矿床的地质和成因探讨 |
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| 引用本文：.1991.A Preliminary Discussion On Geology And Genesis Of Stratabound Uranium Deposits In Late Paleozoic Carbonate Formation Of South China[J].Mineral Deposits,10(4):371~384 |
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| 中文摘要:矿床多出现于晚古生代海盆边缘凹陷中。矿床的产出和分布受泻湖相潮坪碳酸盐沉积所控制。矿体呈似层状、透镜状，与上下围岩整合-准整合接触，沿层分布。矿石即为含铀不纯碳酸盐岩，其特征是色较深，含泥碳质及星散黄铁矿。矿石成分、结构构造、微量元素含量、δ14S、δ18O值与围岩近于一致，唯矿石中铀含量高，达工业采冶要求。近矿围岩蚀变微弱。沥青铀矿U-Pb年龄测定多为57-96 Ma，主要反映矿石的后生改造年龄，但部分沥青铀矿年龄(380 Ma)与所在地层时代(D1)相近，表明成岩成矿期矿石仍有存在。且后生改造、叠加富集作用主要发生在原有矿层内，使矿体(层)仍保留原地-准原地特征，因而，应属沉积成岩成矿为主兼有后生改造的层控铀矿床。矿床的形成经历了沉积、成岩成矿和改造富化三个阶段。 |
| 中文关键词:产铀碳酸盐岩建造 成岩成矿 改造富集 层控铀矿床 |
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| A Preliminary Discussion On Geology And Genesis Of Stratabound Uranium Deposits In Late Paleozoic Carbonate Formation Of South China |
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| Abstract:Stratabound uranium deposits in carbonate formation of South China mostly occur in marginal depressions of the Late Paleozoic seabasin adjacent to the post-Caledonian upwarping area. The uraniferous carbonate formation is a suite of tidal flat sediments of lagoon facies characterized by richness in uranium and existence of pelitic and carbonaceous materials as well as dissemihated pyrite. Ore bodies, stratoid and lenticular in form, show conformable or nearly conformable contact with overlying and underlying strata; an ore body(bed) and its wall rocks make up a sequence of ore-bearing rocks, indicating that ore bodies still preserve autochthonous or semi-autochthonous characters. Ores are simply uraniferous micritie bioclastic limestone, micritic limestone containing bioclastic materials, limestone of breccia fragments, fine-crystalline dolemite and argillite. Uranium in ores occurs mainly as disseminations adsorbed by pelitic and carbonaceous materials, and partly as independent minerals such as pitchblende. The near-ore wall rocks have only suffered weak alteration. Ore-forming temperatures are in the range of 250-89℃, 34S values of pyrite are +10 - 24‰, and 18OSMOW values of carbonate minerals are +8.81 - +17.31‰. Ores are basically consistent with wall rocks in mineral and chemical composition, 34S values and 18O values. U-Pb ages of pitchblende are mostly 96-57 Ma with rather remarkable time difference between ore and rock, indicating obvious epigenetic transformation which, however, mainly took place within the original ore beds.It is therefore Considered that these ore deposits are stratabound uranium deposits in carbonate formation. The ore-forming process of these uranium deposits consists of the following three stages: (1) synsedlmentary stage, forming uraniferous lime mud layer; (2) diagenetlc-metallogenic stage, at which sediments were consolidated to form primitive ore bed first, and then the adsorbed uranium in this bed was partly crystallized to form microgranular pitchblende due to the deep-buried effects; (3) epigenetic enrichment stage, when superimposition and enrichment of uranium took pl ace in the original ore bed as a result of transformation by underground water or heated water. |
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