Ar-40/Ar-39 dating of deformation events and reconstruction of;exhumation of ultrahigh-pressure metamorphic rocks in Donghai, East;China

	Ar-40/Ar-39 dating of deformation events and reconstruction of;exhumation of ultrahigh-pressure metamorphic rocks in Donghai, East;China
	Li, JY; Yang, TN; Chen, W; Zhang, SH
刊名	ACTA GEOLOGICA SINICA-ENGLISH EDITION
	2003
卷号	77 期号:2 页码:155-168
关键词	ultrahigh-pressure metamorphic rocks structural deformation Ar-40/Ar-39 dating exhumation Donghai East China
ISSN号	1000-9515
英文摘要	Recent investigations reveal that the ultrahigh-pressure metamorphic (UHPM) rocks in the Donghai region of East China underwent ductile and transitional ductile-brittle structural events during their exhumation. The earlier ductile deformation took place under the condition of amphibolite facies and the later transitional ductile-brittle deformation under the condition of greenschist facies. The hanging walls moved southeastward during both of these two events. The Ar-40/Ar-39 dating of muscovites from muscovite-plagioclase schists in the Haizhou phosphorous mine, which are structurally overlain by UHPM rocks, yields a plateau age of 218.0 +/- 2.9 Ma and isochron age of 219.8Ma, indicating that the earlier event of the ampibolite-facies deformation probably took place about 220 Ma ago. The Ar-40/Ar-39 dating of oriented amphiboles parallel to the movement direction of the hanging wall on a decollement plane yields a plateau age of 213.1 +/- 0.3 Ma and isochron age of 213.4 +/- 4.1 Ma, probably representing the age of the later event. The dating of pegmatitic biotites and K-feldspars near the decollement plane from the eastern Fangshan area yield plateau ages of 203.4 +/- 0.3 Ma, 203.6 +/- 0.4 Ma and 204.8 +/- 2.2 Ma, and isochron ages of 204.0 +/- 2.0 Ma, 200.6 +/- 3.1 Ma and 204.0 +/- 5.0 Ma, respectively, implying that the rocks in the studied area had not been cooled down to closing temperature of the dated biotites and K-feldspars until the beginning of the Jurassic (about 204 Ma). The integration of these data with previous chronological ages on the ultrahigh-pressure metamorphism lead to a new inference on the exhumation of the UHPM rocks. The UHPM rocks in the area were exhumed at the rate of 3-4 km/Ma from the mantle (about 80-100 kin below the earth's surface at about 240 Ma) to the lower crust (at the depth of about 20-30km at 220 Ma), and at the rate of 1-2 km/Ma to the middle crust (at the depth of about 15 kin at 213 Ma), and then at the rate of less than I km/Ma to the upper crust about 10 km deep at about 204 Ma.
学科主题	变质岩岩石学
WOS关键词	COESITE-BEARING ECLOGITES ; NORTHEASTERN JIANGSU ; YANGTZE CRATONS ; COLLISION ; DABIE ; NORTH ; PROVINCE ; REGION ; BLOCKS ; LU
WOS研究方向	Geology
语种	英语
出版者	GEOLOGICAL SOC CHINA
WOS记录号	WOS:000184210600003
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/37576]
专题	中国地质科学院地质研究所
作者单位	Chinese Acad Geol Sci, Inst Geol, Beijing 100037, Peoples R China.
推荐引用方式 GB/T 7714	Li, JY,Yang, TN,Chen, W,et al. Ar-40/Ar-39 dating of deformation events and reconstruction of;exhumation of ultrahigh-pressure metamorphic rocks in Donghai, East;China[J]. ACTA GEOLOGICA SINICA-ENGLISH EDITION,2003,77(2):155-168.
APA	Li, JY,Yang, TN,Chen, W,&Zhang, SH.(2003).Ar-40/Ar-39 dating of deformation events and reconstruction of;exhumation of ultrahigh-pressure metamorphic rocks in Donghai, East;China.ACTA GEOLOGICA SINICA-ENGLISH EDITION,77(2),155-168.
MLA	Li, JY,et al."Ar-40/Ar-39 dating of deformation events and reconstruction of;exhumation of ultrahigh-pressure metamorphic rocks in Donghai, East;China".ACTA GEOLOGICA SINICA-ENGLISH EDITION 77.2(2003):155-168.