摘要
新疆库鲁克塔格基性岩墙群的四个样品的ＫＡｒ表观年龄为４５５６７３Ｍａ，等时年龄为２８７±１３Ｍａ。这一年龄与近几年报道的沿天山构造带的早二叠世火山岩年龄一致。氩初始值为５０８，在Ｐ型岩浆范围内，结合稀土、微量元素特征。
There has been increasing interest in the study of dyke swarms which are related to
rifting and continental break up Kuluktag dyke swarms are located in the northeast part of
Tarim Basin, Xinjiang, China The dykes, parallel to each other, intruded into the Archaean and
early Proterozoic rocks Four samples collected from the dykes are dated with K Ar method
The apparent ages are discordant, ranging from 455 to 673 Ma Using the Ludwing's ISOPLOT,
an isochron age of 287±13 Ma was obtained with a correlation cotfficicent of 0 9850, This age
is concordant with the ages of volcanic rocks along the Tianshan Mt structure zone dated
around 280 Ma The K Ar isochron method has some advantage for dating mafic dykes: (1)
These rocks are often fresh and slightly affected by alteration; (2) The closure temperature of
mafic rocks for argon is high; (3) The measurement precision of mass spectrometer is much
higher than it was before, so that low K samples can be well measured; The potassium
abundance of mafic dykes is about 0 5 1 5% and suitable for K Ar dating; (4) The whole rock
method is used, so that the tough work of selecting monomineral fraction is not necessary
Moreover, the initial argon can be eliminated by this method, but the atmospheric argon must
be removed in the experimental process Igneous rocks originated from different sources have
different initial argon ratios The initial argon ratio for Kuluktag dykes is 508, belonging to
mantle plume type according to Kaneoka and Takaoka (1985) We infer that the magma of the
dykes originated from “enriched mantle” The REE and trace elements features of the dykes
are also typical of “enriched mantle” and are in good agreement with those of basalts related
to plume
出处
《高校地质学报》
CAS
CSCD
1999年第1期54-58,共5页
Geological Journal of China Universities
基金
国家"九五"重点科技攻关资助
关键词
库鲁克塔格
基性岩墙群
等时年龄
钾-氩
mafic dykes, K Ar isochron age, 40 Ar/ 36 Ar initial ratio
mantle plume
