痕量元素和碳氧同位素在塔里木盆地西南缘棋盘组沉积环境研究中的应用

Application of trace elements and carbon-oxygen isotopes on the research of sedimentary environment of the Qipan Formation in the southwest margin of Tarim Basin,China

以塔里木盆地西南缘中二叠统棋盘组为例,通过痕量元素和碳氧同位素对古盐度、古气候和氧化还原环境进行分析,进而恢复沉积环境。用ICP-MS光谱仪和MAT-251稳定同位素质谱仪分别对棋盘组样品进行痕量元素和碳氧同位素测试分析,选取B含量、B/Ga、Sr/Ba和V/(V+Ni)和碳氧同位素作为判别沉积环境的指标,分析结果表明棋盘组主要发育在盐度较高、温暖-炎热的近岸海相沉积环境和有利于有机质形成的贫氧-厌氧环境;分析垂向上痕量元素和碳氧同位素参数与海平面变化的关系,认为参数的变化与海平面升降有一定的相关性,棋盘组下段整体上表现为一个海退到海侵的过程,其中有4次完整的次级旋回,由于海平面的不断变化使得棋盘组岩性表现为泥岩和生物碎屑灰岩的频繁互层。

Parameters of trace elements and carbon-oxygen isotopes are used to analyze the paleosalinity, paleoclimate and oxidation-reduction environlnent and reconstruct the sedimentary environment of the Middle Permian Oipan Formation in the southwest margin of Tarim Basin. The values of trace elements and carbon-oxygen isotopes are measured by ICP-MS spectrometer and MAT- 251 stable isotope mass spectrometer, respectively. B, B/Ga, Sr/Ba 和 V/（V＋ Ni） and carbonoxygen isotopes are used as indicators to determine the depositional environment. It shows that the Qipan Formation formed in a high salinity on shore marine sedimentary environment with a warm to dry climate, and in poor oxygen to anaerobic environment favorable to the enrichment of organic matter. It considers that the trace elements and carbon-oxygen isotopes parameters are closely related to the sea level changes. The Qipan Formation shows a regressive to transgressive process with four sub-cycles, and the variation of sea-level results in the frequent occurrence of interbeds of mudstone and bioclastic limestone in Qipan Formation.