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1800Ma,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1778±20 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）,1776～1800Ma为火山岩的形成年龄;将1800Ma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1800Ma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1700Ma,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1650Ma,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,1700Ma、1650Ma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.1600Ma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1800Ma伸展裂解作用的最终结束时期.1600Ma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�
The lower boundary age of the 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 Ltiliang Mountains area in Shanxi Province, the Zhongtiao Mountains in South Shanxi Province and the Xiongrersban 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 1778 ±20 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 and 1779±29 Ma （dated for the volcanic rocks）. It seems reasonable to take the 1800 Ma as the lower boundary age of the Xiaoliangling Formation and the 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 the Xiong＇er Group） are the sediment covers after the rifting at 1800 Ma. The volcanic rocks from the Xiaoliangling Formation and the Xiong＇er Groupare 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 the Changzhougou Formation, Changcheng System. The weathering residuum, overlap the Miyun rapakivi granites, is dated at 1650 Ma, represents the time began to accept the deposits after the rifting of Aulacogen in Miyun area, Beijing. It is not the age of the lowest layer in Changzhougou Formation. The different age both 1700 Ma and 1650 Ma indicate the lower boundary ages o
出处
《地质学报》
EI
CAS
CSCD
北大核心
2014年第9期1623-1637,共15页
Acta Geologica Sinica
基金
大陆构造与动力学国家重点实验室自主基金项目(编号Z1301-a3)
中国地质调查项目(编号12120114064301)
国家自然科学基金项目(编号41073014
41373052)共同资助的成果
关键词
华北克拉通
裂陷槽
超大陆
中元古界
常州沟组
小两岭组
汉高山群
熊耳群1800
MA
North China Craton
aulacogen
supercontinent
Meso-proterozoic
Changzhougou Formation
Xiaoliangling Formation
Hangaoshan Group
Xiong＇ er Group
1800 Ma
