吐哈盆地南缘晚石炭世火山活动及其对沉积环境的影响  

LATE CARBONIFEROUS VOLCANIC ACTIVITY AND ITS INFLUENCE ON SEDIMENTARY ENVIRONMENT IN THE SOUTHERN MARGIN OF TURPAN-HAMIBASIN

作　　者：陈旋 苟红光 蔡鑫勇 徐雄飞 张薇 张琪 刘俊田 蒋威 谭先锋 CHEN Xuan;GOU Hongguang;CAI Xinyong;XU Xiongfei;ZHANG Wei;ZHANG Qi;LIU Juntian;JIANG Wei;TAN Xianfeng(Research Institute of Erploration and Development,Tuha Oilfield Com pany,PetroChina,Hami 839009,China;College of Petroleum and Natural Gas Engineering,Chongqing University of Science and Technolo-gy,Chongqing401331,China;Chongqing Key Laboratory of Erploration and Development of Compler Oil and Gas Fields,Chongqing 401331,China)

机构地区：[1]中国石油吐哈油田分公司勘探开发研究院,新疆哈密839009 [2]重庆科技大学石油与天然气工程学院,重庆401331 [3]复杂油气田勘探开发重庆市重点实验室,重庆401331

出　　处：《矿物岩石》2024年第3期165-180,共16页Mineralogy and Petrology

基　　金：国家自然科学基金面上基金项目(批准号:42072140);重庆市杰出青年科学基金项目(编号:CSTB2022NSCQ-JQX0031);中国石油吐哈油田分公司科研项目(编号:YJYHZC2022089)。

摘　　要：吐哈盆地台南凹陷石炭统底坎尔组沉积时期发育多层火山岩和火山碎屑岩夹层,其火山活动对沉积环境的影响尚不明确。本研究利用7口钻录井资料、49块样品的镜下微观和主量元素、微量元素分析,研究其火山活动及其对沉积环境的影响。研究表明,底坎尔组火山岩含较高的w(SiO_(2))(>56%)和强-中等的Eu负异常(δEu=0.36~0.79,平均值为0.64),其A/CNK<1.1,(La/Yb)_(N)的变化范围为1.84~5.84,显示出英安质-流纹质成分的特征。其亏损Nb、Ta、Ti等高场强元素,与大陆弧岩浆岩类似,可能来源于下陆壳的变基性岩部分熔融作用。同时可在底坎尔组碎屑岩镜下薄片中观察到大量中-酸性火山碎屑,其主量元素与火山岩样品重叠,w(SiO_(2))的变化范围为54.09%~75.55%,ΣREE的变化范围为85.5×10^(-6)~125.0×10^(-6),弱-中等负Eu异常(Eu=0.57~0.80,平均值为0.67)。基于原始地幔标准化模式,上述碎屑岩显示与中-上大陆地壳类似的地球化学特征,表明主要为中-酸性火山弧的岩浆碎屑来源。构造判别图指示,底坎尔组碎屑岩沉积于大陆岛弧的构造背景,与同期火山岩一致。因此,底坎尔组火山岩和碎屑岩形成于北天山洋俯冲至吐哈盆地下方,俯冲流体和地幔热源诱发了下陆壳发生大规模部分熔融,强烈的火山活动导致底坎尔组从下至上碎屑岩的中基性火山碎屑的物源成分逐渐增多。结合泥岩反映的古气候、古环境和古生产力等指标,上石炭统底坎尔组的沉积时期,古气候条件由干燥转向潮湿,火山源区的化学风化程度增强,沉积环境的古盐度增高且还原性增强,对初级生产力具有明显的破坏作用,但有利于有机质的保存。In Tainan Sag of Turpan-Hami Basin,there were plenty layers of volcanic rocks and volcani-clastic layers formed during the sedimentary period of the Carboniferous Decaner Formation,and the influ-ence of volcanic activity on the sedimentary environment is not clear.This investigation utilizes data from 7 drilling and logging wells,microscopic thin section observations of 49 samples,and analyses of major and trace elements within the rocks to unravel their influence on sediments.Geochemical analysis reveals that the volcanic rocks of the Dikaner Formation exhibit high SiO2 content(>56%),along with moderate to strong negative Eu anomalies(Eu=0.36-0.79,average 0.64),an A/CNK value of less than 1.1 and(La/Yb)n ratios ranging from 1.84 to 5.84,indicative of a dacitic-rhyolitic composition.These rocks show a depletion in high field strength elements such as Nb,Ta,and Ti,similar to continental arc mag-matic rocks,suggesting their origin from partial melting of metabasic rocks in the lower continental crust.The Dikaner Formation contains numerous medium-acid pyroclasts whose major elements overlap with volcanic rock samples.These pyroclasts exhibit varying SiOz content(54.09-75.55%)and ZREE ran-ging from 85.5×10^(-6) to 125.0×10^(-6),with a weak to medium negative Eu anomaly(δEu=0.57-0.80,mean 0.67).Based on the mantle-normalized model,these pyroclastic rocks share geochemical character-istics similar to the middle-upper continental crust,suggesting they are predominantly magmatic clastic sources within the medium-acid volcanic arc.The tectonic discrimination diagram for the Dikaner Forma-tion indicates that the detrital rocks were deposited in a continental island arc setting,consistent with the volcanic rocks of the same period.It is inferred that both the volcanic and clastic rocks of the Dikaner For-mation were formed during the subduction of the North Tianshan Ocean beneath the Turpan-Hami Basin.Subduction fluids and mantle heat triggered extensive partial melting of the lower continental crust,lead-ing to intense

关 键 词：底坎尔组 火山活动 沉积环境 晚石炭世 吐哈盆地 

分 类 号：P532[天文地球—古生物学与地层学] P59[天文地球—地质学]