摘要
在信江盆地中存在数层和石炭纪海相火山岩及其海底块状硫化物矿层相伴生，与石炭纪地层整合产出的层状硅质岩。由对硅质岩常量元素、微量元素、稀土元素、硅和氧同位素等地球化学特征研究表明，本区硅质岩具有一定的热水沉积硅质岩地球化学特征。在Ａｌ－Ｆｅ－Ｍｎ和Ｆｅ－Ｍｎ－（Ｎｉ＋Ｃｏ＋Ｃｕ）三角图上，本区硅质岩属热水沉积硅质岩。由硅质岩ＭｎＯ／ＴｉＯ２比值、δＣｅ值和δ３０Ｓｉ值分析表明，信江盆地石炭纪硅质岩的沉积环境主要为浅海。
お? There are bedded cherts associated with sea volcanic rocks and massive sulfide orebeds in sea floor of Carboniferous period in Xinjiang Basin. These bedded cherts are conformity with the Carboniferous system and they have a same occurrence. The volcanic rocks are mainly rhyolotes, dacites and volcanic tuffs. All the volcanic rocks have been argillized. The straum of carbonate rocks has a clear sedimentary stratification. The cherts are chiefly scattered the neighbouring of the DongxiangYongping fault which is the boundary fault in Xinjiang basin. The thickness of chert sequence varies from several to 20m. The colors of cherts are grey brown and black. There are sedomentary stratifications in these bedded cherts. Quartz and flint are the main mincrals. The contents of quartz and flint are over 85%. The cherts have comparatively high contents of SiO2, TiO2, Al2O3, Fe2O3, FeO, MnO, MgO, CaO, Na2O, K2O and P2O5. They are typical hydrothermal cherts in the AlFeMn triangle diagram. And twenty projection spots of cherts in this area are all situated in the area of hydrothermal cherts. The cherts have high contents of As, Sb, Bi, Ga, U. And the most U/Th values of cherts are over 1. They have trace element characteristics of hydrothermal sediment geochemistry. The cherts in this area are also typical hydrothermal ones in the FeMn(Ni+Co+Cu) trangle diagram. These cherts can also be identified as hydrothermal ones by the following REEgeochemical evidence: First, they have low total contents of REE, ranging from 10.88μg/g to 25.96μg/g. Second, the LREE/HREE ratioes range from 1.07 to 1.66 with comparatively enrichment in HREE. Third, there is slight negative δCe anomaly, and the δCe values range from 0.75 to 0.94 and the averge value is 0.84. Meanwhile, the cherts in this area have the curves in which Ce is a slight negative anomaly and HREE tilts silightly left in the REE distribution pattern for normalized cherts by the North America shale.
出处
《地质科学》
CAS
CSCD
北大核心
1998年第1期39-50,共12页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金
中国有色金属工业总公司基金
关键词
硅质岩
地球化学
热水沉积
沉积环境
盆地
Chert, Geochemistry, Hydrothermal sediment, Sedimentary environment, Xinjiang basin.
