摘要
滇东南地区的铝土矿床,层位时代为晚二叠世乐平期。有两种类型:一种是古风化壳红土型铝土矿床,由基性火山碎屑岩经红土化作用残积而成,红土化在剖面上从上而下逐渐减弱,矿层中仍部分保留了残余火山碎屑结构,一水硬铝石的δ^(18)O值为10.38％(SMOW);另一种是半局限海碳酸盐台地上的碎屑沉积铝土矿,矿层呈单层或复层,产于生物碎屑灰岩与炭质页岩的互层中,矿石中除常见的碎屑结构外,尚有蠕状变形的假鲕,其中细粒状、草莓状黄铁矿呈环状分布,表明有部分水铝石可能呈微粒悬浮在水体中后经沉积成岩而聚集成矿,δ^(18)值为15.62-19.29％(SMOW)。这两类矿床均程度不同地发育了氧化带,有的还能形成第四纪岩溶堆积矿床,较原生矿更有工业价值。上述两类铝土矿床在滇东南地区保留十分典型的成因特征标志,有助于当前国内铝土矿床成因的讨论和类型的建立,藉以认识第四纪以前的铝上矿床成矿作用。
The age of horizon of bauxite deposits in Southeastern Yunnan is,Leping of Late Permian. There are two types: One is palaeoweatheringcrust bauxite deposit. It was eluvially formed by iaterization of basic pyroclastic rocks. The laterization gradually weakened from top to bottom on the section. The residual pyroclastic textures are still preserved to some extent in the seams. The S^18O value of diaspore is 10. 38‰(SMOW). Another is clastic sedimentary bauxite deposit on the carbonate plateau of semiconfined sea The seams occur as a single bed or multiple beds in the interlaies of bioclastic limestones and car-bonaceous shales. In the ores, there are oolitic deformed pseudo-oolithes besides common clastic textures. The fine-grained and strawberry-shaped pyrites are distributed as ringshapes in the pseudo-oolithes, These show that parts of empholites could have suspended as micrograins in water and be condensed into deposits after they were sedimentated as rocks. The S^18O value is 15. 62-19.29‰(SMOW). The oxidized zones which differ in degree develop in the two deposits. Some of them could have become karst accumulative deposits of Qu-aternary, and these deposits possess more economic value than the primary deposits. The very typical genetic markers are preserved in the two bauxite deposits above-mentioned in Southeastern Yunnan, which contributes to, at present and domestically, the discussion of the genesis of bauxite deposits and the establishment of their types, and to the understanding of the mineralization of bauxite deposits before Quaternary.
出处
《云南地质》
1992年第2期121-129,共9页
Yunnan Geology
