塔里木盆地北缘震旦系苏盖特布拉克组沉积相与物源演化--以塔北隆起XH1井为例

Sedimentary facies and detrital provenance evolution of the Sinian Sugetebulak Formation from northern margin of Tarim Basin:a case study of XH1 well in Tabei uplift

塔里木盆地北部的塔北隆起地区缺乏震旦系野外露头,导致对整个盆地北部的震旦纪地层发育和物源演化等认识不足。以XH1井苏盖特布拉克组岩心样品为研究对象,开展砂岩的碎屑组分、重矿物、碎屑锆石U-Pb-Hf同位素及稀土元素组成研究。测井曲线、岩心岩相变化和重矿物指标显示塔北隆起的苏盖特布拉克组为潮坪相。碎屑锆石U-Pb年龄分为2900~2400、2300~1600、1100~900和750~580 Ma 4组,苏盖特布拉克组的最大沉积年龄不早于572 Ma。重矿物和碎屑锆石显示其母岩主要为酸性岩浆岩和少量基性-超基性岩,物源主要来自于盆地东北缘的库鲁克塔格地区,其次为北部的塔北隆起、东南缘阿尔金—敦煌地区,以及西南缘的西昆仑地区,少量来自中天山微陆块。大部分古元古代碎屑锆石的εHf(t)为负值,少量的碎屑锆石εHf(t)为正值,两阶段模式年龄T DMC介于3474~2360 Ma,主要来源于古元古代的古老地壳物质改造,少量来源于幔源岩浆输入或新生地壳的物源区。新元古代碎屑锆石εHf(t)主要为负值,两阶段模式年龄T DMC介于4032~1485 Ma,表明其物质来源于太古代至中元古代的古老地壳物质改造。塔里木北缘在震旦纪苏盖特布拉克期为碰撞背景。

The Tabei uplift from the north of Tarim Basin lacks Sinian outcrops,resulting in a lack of understanding of the Sinian stratigraphic development and provenance evolution.In this study,the detrital components,heavy minerals,detrital zircon U-Pb-Hf isotopic and REE data for the sandstone of the Neoproterozoic Sugetebulak Formation,were studied based on the XH1 well from the Tabei uplift.According to the logging curves,core facies transformation and heavy mineral indexes,it is concluded that the Sinian Sugetebulak Formation in Tabei uplift deposited in tidal flat environment.The U-Pb ages of detrital zircons are divided into four groups:2900-2400,2300-1600,1100-900,and 750-580 Ma.The maximum depositional age of the Sugatebulak Formation is no earlier than 572 Ma.The heavy minerals and detrital zircons indicate that the parent rocks are mainly acidic magmatic rocks with small amount of basic-ultrabasic rocks.The provenance is mainly from the Kuruqtage area and its vicinity,the eastern basement of the Tarim Basin and the West Kunlun area,with a small amount from the central Tianshan microcontinent.Paleoproterozoic zircons yield Hf model ages(T DMC)range from 3474 Ma to 2360 Ma,and some Paleoproterozoic zircons show positiveεHf(t)values,indicating zircons were derived from juvenile mantle-derived material at those periods.However,most Paleoproterozoic zircons show negativeεHf(t)values,suggesting the crustal reworking was the dominant process from Archaean to Paleoproterozoic.The Neoproterozoic detrital zircons have negativeεHf(t)values and yield Hf model ages(T DMC)range from 4032 Ma to 1485 Ma,which suggest that the Neoproterozoic detrital zircons were derived from reworking of the ancient Archaean to middle Proterozoic.Based on the data of this study and previous data,it is considered that the northern margin of Tarim Basin was the collision background during the Sugetebulak period.