塔里木板块新元古代地层化学蚀变指数研究及其意义  

Study on the chemical index of alteration of Neoproterozoic strata in the Tarim plate and its implications.

作　　者：刘兵[1] 徐备[1] 孟祥英[2] 寇晓威[2] 何金有[1] 卫巍[1] 米合[3] 

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [2]吉林省第三地质调查所,四平136000 [3]河北省地勘局第三地质大队,张家口075000

出　　处：《岩石学报》2007年第7期1664-1670,共7页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40572133;40032010)的资助.

摘　　要：本文应用化学蚀变指数(CIA)方法,研究新疆库鲁克塔格地区新元古代地层,并探讨沉积时期的气候环境。贝义西组总体 CIA 值较低,介于51～56之间,具冰期环境特征。照壁山组 CIA 值为60左右,表明气候有所变暖。阿勒通沟组的CIA 值变化范围在48～61之间,顶部突变为69～71,说明阿勒通沟期经历了另一次寒冷事件,并以温暖环境结束。其上的特瑞爱肯组 CIA 值介于49～53之间,说明第三次经历寒冷干燥的气候环境。扎莫克提组,育肯沟组和水泉组的 CIA 均值为65,反映温暖条件下的沉积环境。新元古代末期汉格尔乔克组 CIA 值下降为56,暗示第四次出现寒冷气候环境。以上特征表明新疆库鲁克塔格地区新元古代的气候环境出现四次冷热交替变化。其中尤为重要的是阿勒通沟组中下部应为寒冷气候环境,而顶部突变为温暖气候环境,因此该组反映了一次明确的从冷到暖的气候变化过程,可以作为贝义西冰期和特瑞爱肯冰期之间的另一次独立冰期。本文的研究成果从地球化学角度支持塔里木板块新元古代四次冰期的划分方案。通过与扬子板块新元古代冰期划分方案的对比,认为塔里木板块新元古代四次冰期的前三次均已在华南板块以冰期或寒冷环境沉积形式出现。The method of Chemical Index of Alteration （CIA） is applied to the researches of Neoproterozoic strata in Quruktagh and the discussion of paleoclimate changes, The experimental data show that samples of the Beiyixi Formation are characterized by low CIA value, ranging from 51 to 56, implicating the glacier environment. The CIA values of the samples of the Zhaobishan Formation are about 60, showing a warmer paleoclimate, The CIA values of most samples of the Aletonggol Formation range from 48 to 61 and abruptly rise to 69 -71 in the top, showing another cold event during the Altonggol period ended by a warm environment. The CIA values range from 49 to 53 in the following Tereeken Formation, implying the third cold period. The average CIA value of the Zhamoketi, Yukengou and Shuiquan formations is 65, suggesting a warm sedimental condition, The CIA values of the Hankalchough Formation fall to about 56, implicating the forth cold event during the terminal Neoproterozoic. The evidences above show that there were four warm-cold conversions in the Neoproterozoic in Quruktagh, Xinjiang. Among these, the key issue is the cold-warm conversion abruptly happened within the Aletonggol period, which indicates a distinct process from cold to warm and can be regarded as another independent ice age between the Beiyixi and the Tereeken ice ages, This research supports the hypothesis of quartered ice age in the Tarim plate in the Neoproterozoic. By a correlation of the Neoproterozoic ice ages between Tarim and Yangtze plates, the former three of the four ice ages in the Tarim plate can be traced in Yangtze plate.

关 键 词：新元古代 化学蚀变指数 塔里木板块 古气候 

分 类 号：P594.2[天文地球—地球化学] P534.3[天文地球—地质学]