摘要
本文首次利用碳酸盐岩 C,O,Sr稳定同位素探讨了羌塘盆地那底岗日地区中侏罗世海洋沉积环境的演变。测试结果表明 ,该区中侏罗世碳酸盐岩δ1 3C,δ1 8O及 N(87Sr) / N(86 Sr)值分别为 - 3.2 5× 10 - 3～ +3.30 4× 10 - 3,- 11.419× 10 - 3～ - 3.2 8× 10 - 3及 0 .70 70 2～ 0 .70 86 2 ,并伴生了多次升降变化。分析认为 ,δ1 3C值主要受沉积环境的水介质盐度、氧化 -还原条件、生物发育程度及有机质埋藏速率的影响 ;δ1 8O值主要与沉积环境的盐度、温度、海平面升降及沉积期后成岩作用等因素有关 ;N(87Sr) / N(86 Sr)值则由三种不同锶源在海水中的组成比例所决定。因此 ,C,O,Sr同位素组成及演化可以直接或间接地反映古环境的变迁 ,从而为那底岗日地区中侏罗世古海洋沉积环境的分析提供了可靠的地质地球化学依据。
This paper discussed the evolution of the middle Jurassic oceanic sedimentary environment on the basis of C, O and Sr stable isotopic compositions and variations in Nadigangri area,Qiangtang basin.The δ 13 C,δ 18 O and N ( 87 Sr)/ N ( 86 Sr) values of middle Jurassic carbonates are -3.25×10 -3 ^+3.304×10 -3 ,-11.419×10 -3 ^-3.28×10 -3 and 0.707 02~0.708 62 respectively. These values went up and down for several times in middle Jurassic.It is suggested that δ 13 C values are mainly influenced by salinity,oxidation reduction condition,the extent of organism developed and the rate of organic matter buried and so on; δ 18 O values are chiefly relevant to salinity,temperature during deposition and postdepositional diagenesis;and that N ( 87 Sr)/ N ( 86 Sr) values are controlled by the variable proportions of three different Sr sources in seawater.As a result,the compositions and evolution of C, O and Sr isotope may directly or indirectly reflect the evolution of palaeo environment,and provide some reliable and quantitative geological geochemical information for analyzing the middle Jurassic oceanic-sedimentary environment in Nadigangri area.
出处
《矿物岩石》
CAS
CSCD
北大核心
2000年第1期80-86,共7页
Mineralogy and Petrology
基金
原中国石油天然气总公司青藏油气项目资助
关键词
碳酸盐岩
碳
氧
锶
同位素组成
演化
古海洋沉
Nadigangri Area
Middle Jurassic carbonate
C
O and Sr isotopic compositions and variation
controlled factors
palaeo oceanic sedimentary environment
