华北克拉通中元古界底界年龄与盆地性质讨论
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Discussions on the Lower Boundary Age of the Mesoproterozoic and Basin Tectonic Evolution of the Mesoproterozoic in North China Craton
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    摘要:

    国际地层委员会将中元古界底界界线年龄定为1600 Ma,1600-1400 Ma为Calymmian(盖层系),表示全球地台盖层形成时期。华北地台基底固结时间为1800 Ma,固结后即进入伸展裂解作用时期,首先是山西吕梁山区、晋南中条山、豫西熊耳山区裂解发展成三叉裂陷槽(Aulacogen)。吕梁山区小两岭组火山岩形成年龄有1763±42 Ma(SHRIMP U-Pb锆石)及1779±20 Ma(LA-ICP-MS U-Pb锆石)两个数值;豫西熊耳群顶部马家河组和中部鸡蛋坪组及下部许山组火山岩年龄分别为1776±20 Ma、1791±20 Ma和1783±13 Ma(SHRIMP U-Pb锆石),1776 -1800 Ma为火山岩的形成年龄;将1800 Ma作为小两岭组与熊耳群两个火山岩组的底界年龄应当是合理的。吕梁山区的汉高山群为碎屑岩夹火山岩,代表吕梁-陕豫三叉裂陷槽北支中的快速充填,与小两岭组为同时期沉积。汉高山群、大古石组(熊耳群底部沉积岩)为1800 Ma裂解开始的盖层沉积,小两岭组火山岩、相关的辉绿岩墙及熊耳群火山岩均为裂解时期的岩浆作用产物。北京密云环斑花岗岩侵位时间为1700 Ma,代表燕山-太行山裂陷槽裂解的起始时间也即燕山地区长城系常州沟组底界年龄。北京密云地区环斑花岗岩风化壳上覆常州沟组年龄可确定为1650 Ma,它不应被看作常州沟组最低层位的年龄,而是裂陷槽裂解后密云地区开始接受沉积的年龄,1700 Ma、1650 Ma代表常州沟组在不同地区的底界年龄,但均不等于长城系或中元古界的底界年龄。1600 Ma为高于庄组底界年龄,即长城系与蓟县系的界线年龄,也是国际地层委员会中元古界的底界年龄。1600 Ma代表燕山-太行山裂陷槽闭合的年龄,也是华北地台始自1800 Ma伸展裂解作用的最终结束时期。1600 Ma是新的陆表海盆地发展的起始时间,是重要的华北地台构造转换的时期。因此,1800与1600 Ma代表华北地台重大地质构造事件的年龄,具大区域构造意义,依据对前寒武系界线年龄确定的原则,两个年龄值均可被选择为中元古界底界的界线年龄。但本文赞同中国全国地层委员会采用1800 Ma作为中元古界的底界年龄,因其更符合中国的地质构造实际:华北地台裂解-克拉通内裂陷槽中的盖层充填,底界为1800 Ma。 华北地台中元古界盆地在不同时期,它的构造性质完全不同:1800~1600 Ma为裂陷槽;1600~1400 Ma发展成陆表海;1400~1300 Ma转化为弧后盆地;1800 Ma、1600 Ma及1400 Ma代表中元古代三个重要的区域构造转换的时间点。

    Abstract:

    The lower boundary age of Mesoproterozoic is positioned at 1600 Ma by International Commission on Stratigraphy (ICS), and the global platform covers are formed at Calymmian with time span of 1600 Ma to 1400 Ma. The North China Platform entered an epoch of extension-broken after its consolidated at 1800 Ma. Then the Luliang Mountains area in Shanxi Province, the Zhongtiao Mountains in South Shanxi Province and the Xiong’ershan area in Western Henan Province are split into a trigeminal Aulacogen. The SHRIMP and LA-ICP-MS zircon ages of the volcanic rocks from Luliang Xiaoliangling Formation are 1763±42 Ma and 1779±20 Ma respectively; and the SHRIMP zircon ages have been obtained from Xiong’er Group in Western Hennan Province are 1776±20 Ma (dated for the volcanic rocks) and 1779±29 Ma. It seems reasonable to take the 1800 Ma as the lower boundary age of the Xiaoliangling Formation and Xiong’er Group. The rocks of Hangaoshan Group of Luliang Mountains area are siliciclastic with volcanic rocks, deposited at the same time with Xiaoliangling Formation, which suggest the quick filling of the north part of Luliang-Shanxi-Henan trigeminal Aulacogen. The Hangaoshan Group and the Dagushi Formation (sedimentary rocks deposited at the bottom of Xiong’er Group) are the sediment covers after the rifting at 1800 Ma, the mafic dykes related to the volcanic rocks from Xiaoliangling Formation and the volcanic rocks from the Xiong’er Group are the products of magmatism in the stage of broken-up. The Miyun rapakivi granites from Beijing are emplaced at 1700 Ma, which indicate the start time of the broken up of the Yanshan-Taihangshan Aulacogen and the lower boundary age of Changzhougou Formation, Changcheng System. The weathering crust, overlap the Miyun rapakivi granites, is dated at 1650 Ma, represents the time began to accept the deposits after the rifting of Aulacogen. It is not the age of the lowest layer in Changzhougou Formation. The age 1700 Ma and 1650 Ma are the lower boundary ages of different areas in Changzhougou Formation. but it’s not equal to the lower boundary age of Changcheng System or Mesoproterozoic. The lower boundary age of the Gaoyuzhuang Formation is 1600 Ma, as the boundary age of Changcheng System and Jixian System. It is not only the close time of Yanshan-Taihangshan Aulacogen, but also the end of the extension-broken time of North China Platform from 1800 Ma. The new epicontinental basin began to develop at this time, and the North China Platform experienced tectonic transformation. Therefore, the significant tectonic events affected North China Platform at 1800 Ma and 1600 Ma, which reflect great regional tectonic implications. According to the determination principle of Pre-cambiran boundary age, both the two ages are used to be the lower boundary of Mesoproterozoic. But in this paper, we approve of 1800 Ma as the lower boundary age of Mesoproterozoic, because of it’s more in line with the Chinese tectonic: 1800 Ma is the lower boundary age of the platform covers from the North China Platform to intra-craton Aulacogen. There are different tectonic settings of the basins in the North China Craton at Mesoproterozoic at different times: it is Aulacogen at 1800~1600 Ma, then develop to epicontinental sea at 1600~1400 Ma, at last transfer to arc-back basin at 1400~1300 Ma; 1800 Ma、1600 Ma and 1400 Ma are three time points of regional tectonic transformation at Mesoproterozoic.

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乔秀夫,王彦斌.2014.华北克拉通中元古界底界年龄与盆地性质讨论[J].地质学报,88(9):1623-1637.
QIAO Xiufu, WANG Yanbin.2014. Discussions on the Lower Boundary Age of the Mesoproterozoic and Basin Tectonic Evolution of the Mesoproterozoic in North China Craton[J]. Acta Geologica Sinica,88(9):1623-1637.

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  • 收稿日期:2014-07-22
  • 最后修改日期:2014-08-24
  • 录用日期:2014-08-25
  • 在线发布日期: 2014-09-16
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