宣龙坳陷中元古界高于庄组沉积相与地球化学特征

宣龙坳陷中元古界长城系高于庄组地层主要为一套碳酸盐岩沉积,通过对该地区野外观察、测量,结合室内薄片资料和地球化学分析,认为该地区高于庄组沉积相为碳酸盐岩台地相,可进一步划分为碳酸盐岩潮坪和生物礁2种亚相及潮上带、潮间带、潮下带、障积-黏结礁4种微相。其中在高于庄组第一段至第八段发育着碳酸盐岩潮坪亚相,高于庄组晚期受滦县抬升运动影响,水体相对变浅,在第九、十段发育着生物礁亚相。对实测剖面49个常量元素、70个微量元素样品分析,按相带进行统计研究,认为研究区碳酸盐岩地球化学特征与原始沉积环境有着极为密切的关系,可作为沉积环境判别的有效标志。其中Sr、Sr/Ba及Sr/Ca值随水体的加深而增大,三者与沉积环境密切相关,用其变化可以来划分沉积相。元素V、Rb、Be值对环境变化敏感,潮上带—潮间带—潮下带具有随沉积水体加深而变大的趋势。

Sedimentary facies and geochemical characteristics of Mesoproterozoic Gaoyuzhuang Fomation in Xuanlong Depression

Mesoproterozoic Gaoyuzhuang Formation in Xuanlong Depression is mainly a carbonate sedimentary system.Through the cautious observation,indoor slice measurement and geochemistry analysis,the author considers that the sedimentary facies of Gaoyuzhuang Formation is carbonate platform facies.It can be furtherly devided into two subfacies including tidal-flat,reef facies and four microfacies consisting of supratidal,intertidal,subtidal zones and barrier product-bond reef.From the first section to the eighth section of Gaoyuzhuang Formation,the tidal-flat facies of carbonate develops.In late phase of Gaoyuzhuang Formation sedimentation,due to the effect of lifting movement of Luan County,the water body becomes relatively shallow.In the ninth and tenth sections,the reef facies develops.Based on the statistics of sedimentary facies,the analysis results of fourty-nine major elements and seventy trace elements show that the geochemical charateristics and sedimentary environment have closely relationship with primary sedimentary environment,and the geochemical characteristics can be regarded as an important mark.Among them,Sr,Sr/Ba and Sr/Ca values increase with the depth of water body,which are closely related to sedimentary environment and can be used to identify the sedimentary facies,The elements V,Rb and Be values are sensitive to the change of environment.They also have increasing characteristics with the depth of water body,such as from supralittoral zone to intertidal zone and to subtidal zone.