滇西北兰坪盆地北部上三叠统含盐层位的厘定及其意义

通过野外实测剖面和大量室内岩矿工作,首次指出兰坪盆地上三叠统至少存在2套含盐层位,上含盐层位于三合洞组上段(T3s2),盐类物质以石膏、天青石为主,下含盐层位于三合洞组下段(T3s1),以天青石为主。天青石和石膏均呈中厚层层状产出,与顶底板地层产状一致。不同地区含盐层岩石组合及序列不同,横向上不具有可对比性,提出其并非正常蒸发沉积产物的认识。同时,含盐地层又是盆地内铅锌矿重要的赋矿层位,因此上三叠统含盐建造层序的厘定对深化认识区域铅锌矿床成矿机制、指导盐类矿床和铅锌矿找矿具有重要的意义。

Sequence stratigraphic definition of Late Triassic salt-bearing horizons in northern Lanping basin of northwestern Yunnan Province and its implications

Based on detailed geological work, the authors investigated three geological sections in Hexi and Dasanjie area within the northern part of Lanping Basin. At least two sets of Upper Triassic gypsum-bearing horizons were identified. The upper horizon is in the upper member of Sanhedong Formation(T3s2) and its salt-bearing materials are quite simple in content, composed mainly of celestine and gypsum with a very small amount of barite. The lower horizon is within the lower member of Sanhedong Formation (T3s1), with the saline material being also made up of celestine. The gypsum-bearing horizons are of the same attitude as the overlying and overlying carbonate layers. The rock associations of the horizons are different in different places, so that the stratigraphic sequences can't be laterally correlated with each other. The salt-bearing horizons present some syn-sedimentation characteristics, but are different from the evaporate deposits formed by evaporation.