摘要
研究四川盆地南部上二叠统龙潭组碎屑岩的地球化学特征,探讨其物源特征及古风化、古环境、古氧化-还原条件等地质意义。通过对CLD1井龙潭组岩心的观察描述和薄片鉴定,结合主元素、痕量元素及稀土元素的测试分析等方法对龙潭组沉积期的沉积环境进行讨论。La/Sc-Co/Th图解、∑REE-La/Yb图解及δEu值分析,以及Al_(2)O_(3)/TiO_(2)-TiO_(2)图解与峨眉山高Ti玄武岩进行对比,结果表明研究区龙潭组物源复杂,主要为峨眉山玄武岩,伴少量钙质泥岩及部分长英质火山岩;Th-Sc-Zr/10和La-Th-Sc三角图分析结果显示龙潭组物源主要来自大陆岛弧;龙潭组样品大陆风化指数平均为85.19,属于中-高强度风化;Sr/Cu质量分数比值介于0.41~26.05(平均值为5.68),MgO/CaO质量分数比值介于0.02~2.35(平均值为0.92),指示龙潭组整体形成于温暖湿润的气候条件,沉积环境为咸水的海陆过渡相环境,晚期为海相沉积环境;古氧化-还原指标[V/(V+Ni)质量分数比值]介于0.59~0.95(平均值为0.81),Th/U质量分数比值介于2.18~5.62(平均值为4.23),Ce_(anom)值介于-0.80~0.10(平均值为-0.01),指示龙潭组沉积水体以贫氧至厌氧的弱氧化至还原性环境为主。龙潭组碎屑岩沉积于温暖湿润条件下的贫氧至厌氧的弱氧化至还原性环境,整体为中-高强度风化,龙潭期沉积水体呈加深趋势。
Through the observation of core description and thin section identification,combined with the analyses of main elements,trace elements and rare earth elements,the geochemical characteristics of Permian Longtan Formation clastic rocks in Well CLD1 in southern Sichuan Basin are studied and the characteristics of its sediment provenance and ancient weathering,paleo-environment,oxidation-reduction conditions and geological significance are discussed.La/Sc-Co/Th diagram,∑REE-La/Yb diagram andδEu value analysis,as well as Al_(2)O_(3)/TiO_(2)-TiO_(2) diagram for the Longtan Formation clastic rocks are compared with the high Ti basalt in Emei Mountain.The results show that the provenance of Longtan Formation in the study area is complex,mainly consisting of Emeishan basalt,with a small amount of calcareous mudstone and part of felsic volcanic rock.Th-Sc-Zr/10 and La-Th-Sc diagrams show that the provenance of the Longtan Formation is mainly from the continental island arc.The average continental weathering index of Longtan Formation samples is 85.19,which belongs to medium-high intensity weathering.Sr/Cu ratio ranges from 0.41 to 26.05(average 5.68),MgO/CaO ratio ranges from 0.02 to 2.35(average 0.92),indicating that the Longtan Formation was formed in a warm and humid climate,and the sedimentary environment was the transitional facies of saline water,and the late stage was the marine sedimentary environment.Paleo-oxidation-reduction index[V/(V+Ni)mass fraction ratio]ranges from 0.59 to 0.95(average 0.81),Th/U mass fraction ratio ranges from 2.18 to 5.62(average 4.23),Ce_(anom) value ranges from-0.80 to 0.10(average-0.01),indicating that the sedimentary water of Longtan Formation is dominated by oxygen-deficient to anaerobic environment.Through the geochemical analysis,it is recognized that the detrital rocks of the Longtan Formation in the study area were deposited in the environment of low oxygen to anaerobic oxidation to reduction under warm and humid conditions,and the overall weathering was medium-high intensity,a
作者
陈聪
林良彪
余瑜
刘冯斌
唐顺成
苏加亮
周文
田景春
CHEN Cong;LIN Liangbiao;YU Yu;LIU Fengbin;TANG Shuncheng;SU Jialiang;ZHOU Wen;TIAN Jingchun(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China)
出处
《成都理工大学学报（自然科学版）》
CAS
CSCD
北大核心
2022年第2期225-238,共14页
Journal of Chengdu University of Technology: Science & Technology Edition
基金
国家自然科学基金项目(41872115)。
关键词
四川盆地
龙潭组
地球化学
古环境
Sichuan Basin
Longtan Formation
geochemistry
paleo-environment
