【摘要】 结合露头剖面、岩石薄片观察、碳氧同位素及微量元素等资料,综合分析了陕西富平地区上奥陶统赵老峪组海相碳酸盐岩沉积时的古水深、古盐度、古温度及氧化还原条件变化规律,以期恢复其沉积环境。研究表明,赵老峪组下部0～12层的δ13C平均值为-0. 95‰、δ18O值为-5. 67‰、Sr/Ba值为80. 31、B/Ga值为7. 93、U/Th值为5. 57、V/Cr值为5. 44,主要是以泥晶灰岩为主的深水原地沉积,其沉积环境总体表现为水体较深、离岸较远、水温较高、盐度较高的贫氧-厌氧环境;上部13～35层δ13C平均值为0. 55‰、δ18O值为-4. 03‰、Sr/Ba值为19. 05、B/Ga值为9. 17、U/Th值为2. 78、V/Cr值为4. 77,主要发育深水原地沉积、重力流沉积和等深流沉积,但深水原地沉积的发育层数相比于下部大大减少,沉积环境逐渐演变为水深相对较浅、水温较低、盐度较低的贫氧-厌氧环境,这一阶段的整体古水深、古温度和古盐度及氧化还原条件相比于0～12层沉积时较稳定,变化幅度较小。结果表明,用地球化学指标研究深水碳酸盐岩沉积时期的海平面变化、古温度、古盐度及氧化还原条件等环境因素也是可行的。更多还原

【Abstract】 An integrated study of field investigation,petrography,carbon and oxygen isotope and trace element geochemistry has been provided on carbonate in the Upper Ordovician Zhaolaoyu Formation in the Fuping area,Shaanxi Province to restore the sedimentary environment. The rocks in 0-12 layers of the Zhaolaoyu Formation have δ13 C of-0. 95‰,δ18 O of-5. 67‰,and Sr/Ba,B/Ga,U/Th and V/Cr ratios of 80. 31,7. 93,5. 57 and 5. 44,respectively,indicative of deep-water sedimentary deposition dominated by micrite limestone. The sedimentary environment is generally represented as an aerobic-anaerobic environment of deep water,far offshore,high water temperature,and high salinity. The upper 13-35 layers haveδ13 C and δ18 O value of 0. 55‰ and-4. 03‰,respectively,and Sr/Ba,B/Ga,U/Th,and V/Cr ratios of 19. 05,9. 17,2. 78 and 4. 77,respectively. They are mainly deep-water sedentary,gravity-flow sediments,and contourites,suggesting that deep-water sedimentary depositions are greatly reduced compared to the lower layers,and the environment was gradually evolved into aerobic-anaerobic environment with relatively shallow water depth,low water temperature,and low salinity. The overall ancient water depth,paleo-temperature,paleo-salinity,and redox condition of this stage was relatively stable during the formation of these layers compared to 0-12 layer. The results show that it is feasible to study the sea level change,paleotemperature,paleo-salinity and redox conditions of deep-water carbonate rocks by geochemical indexes.更多还原