摘要
作者对相当于晋宁运动岩浆活动产物的湖北峡东黄陵岩体和江西九岭岩体分别进行了^(40)Ar/^(39)Ar快中子定年。对采自宜昌莲沱地区的黑云母斜长花岗岩体和黄陵庙黑云母花岗闪长岩体的样品测得两条年龄谱,HH-01黑云母的高温坪年龄为893.7±6.7Ma,HH-05角闪石坪年龄为886.4±4.6Ma。对采自江西宜丰黄岗口的九岭岩体中黑云母测得的高温坪年龄为937.1±6.4Ma。从上述三个年龄值,并综合以前测定的晋宁期侵入体的年龄值以及不整合面上覆盖层和基底最上部沉积层的一些年龄值认为,以900Ma作为震旦系底界年龄是合适的。
Most of Chinese geologists considered that the unconformity marked by the Jinning movement may represent the Sinian lower boundary. The authors suggest in this paper that the boundary age could b? as old as 900 Ma, instead of the ages of 760, 800 and 850 Ma, as suggested by the others.Based on the 40Ar/39Ar step heating techniques, one biotite and one hornblende, both sampled from Huangling granites, yield the plateau ages of 894 + 7 Ma and 886 + 5 Ma respectively. The two concordant ages, no mater whether or not their age spectrum has been disturbed by post-orogenic thermal events, suggest the emplacement age of Huangling intrusion. A similar result, 937 ± 6 Ma, has been obtained for the Jiuling intrusions. Combining with the Rb-Sr and K-Ar ages analysed in this lab and Rb-Sr, U-Pb and K-Ar ages published by the other labs, which both are related to the lower boundary of Sinian, it is indicated that Jinning movement covered a time span ranging from 850 Ma to 1050 Ma, and considering the diachronous of a movement, the authors stress that the age of 900 Ma could be the best estimation of the age of lower boundary of Sinian.
出处
《地质科学》
CAS
CSCD
北大核心
1989年第1期16-25,共10页
Chinese Journal of Geology(Scientia Geologica Sinica)
关键词
氩40
氩39
快中子年龄
~40Ar/~39Ar ages, lower boundary, Sinian, Jinning orogeny, Huanling granites, Jiuling granite
