摘要
文章阐述了烂泥湾地区三叠系不同类型的石膏、硬石膏和杂卤石矿物硫同位素值变化规律,进而探讨了它们的形成条件及其对划分地区地层所起的作用。
Sulfur isotope analysis was made for various types of gypsum, anhydrite and polyhalite from four drill holes in this reconnaissance area. This paper describes δ^(34)S characteristics of veinlike anhydrite, anhvdrite and hydrated anhydrite, sugges- ting that gypsum was mainIy formed by the hydration of anhydriteunder the action of underground water.The microscopic observations of polyhalite, its texture and structure and its sulfur isotopic composition all point to the existence of 'primary' polyhalite and the extensive development of secondary polyhalite(replacement type).Sulfur isotope studies of anhydrite from various sections of Triassic in this area indicate that δ^(34)S values of T_1j^4-T_2l^1 are comparatively stable (between 29-31‰),implying a shallow-water and salinized sedimentary environment. After T_2l^2, δ^(34)S values tended to decrease progressively. Such evolutionary regularity is consistent with things in other areas of Sichuau basin, suggesting a transgressionregression salt-forming environment. It is thus concluded that δ^(34)S values and characteristics of anhydrite may serve as indicators to divide strata, especially strata of evaporates. This result has added to and enriched the knowledge on sulfur isotope composition and evolution of marine Triassic sulfates in the world.
出处
《岩石矿物学杂志》
CAS
CSCD
1991年第2期181-187,共7页
Acta Petrologica et Mineralogica
