共查询到20条相似文献,搜索用时 15 毫秒
1.
Sm-Nd isochron age of ophiolite along northern margin of Altun Tagh Mountain and its tectonic significance 总被引:2,自引:0,他引:2
An ophiolite belt is exposed to the northern edge of Altun Tagh Mountain. Geochronological researches were made on gabbro
and basalt. Sm-Nd isochron age of gabbro is (829 ± 60) Ma, while the age of gabbro mixed basalt is (949 ± 62) Ma. The dating
of Sm-Nd isochron proves that ophiolite formed in (829 ± 60) Ma, which implies that the northern half of Tarim (or north Tarim
Block) had been separated by an ocean from the southern half of Tarim and Qaidarn (or south Tarim Block) until (829 ± 60)
Ma. The south Tarim Block could accrete to the north Tarim Block at the beginning of Sinian, thereby forming the north Altun
Tagh suture. The Sinian system would be the first cover on the amalgamated Tarim craton. 相似文献
2.
A study of the Sm-Nd isotope composition of Honguleleng ophiolite in Xinjiang, China, isochron age ((626±25)Ma),εNd(t) =8.40,and its model age (T
DM
Nd
) in the range of 1 180–1 208 Ma, indicates that the ophiolite was formed in the late stage of the Upper Sinian. In combination
with its facies association, petrochemistry, REE patterns, trace elements and associated chromites orebodies, it is believed
that the Honguleleng ophiolitic magma derived from the LREE-enriched, self-depleted mantle source and formed at paleo-ocean
ridge. This ophiolite is a relic of an oceanic crust within the collision zone. 相似文献
3.
Sm-Nd isochron age evidence for Precambrian metamorphic rocks from the eastern Junggar in northern Xinjiang, China 总被引:1,自引:0,他引:1
《科学通报(英文版)》1996,41(22):1896-1896
4.
Geochronology and Nd and Pb isotope characteristics of gabbro dikes in the Luobusha ophiolite, Tibet 总被引:11,自引:0,他引:11
Su Zhou Xuanxue Mo J. J. Mahoney Shuangquan Zhang Tieyjing Guo Zhidan Zhao 《科学通报(英文版)》2002,47(2):143-146
We report a combined internal and whole-rock Sm-Nd isochron age, and Nd and Pb isotopic data for gabbro dikes of the Luobusha
ophiolite in Tibet. The Sm-Nd isochron of data for two whole rocks and plagioclase and clinopyroxene separates from one of
the rocks yields a Middle Jurassic age of (177±31) Ma (with an initial εNd(t) = +8), which provides a significant bound on the time of formation of the Luobusha ophiolite. The Nd and Pb isotopic characteristics
of the dike indicate an Indian-Ocean-type isotopic affinity, and we conclude that the Luobusha ophiolite formed in an oceanic
setting during the Middle Jurassic. 相似文献
5.
Sm-Nd dating and Nd-Sr isotopic characteristics of the Shimian ophiolite suite, Sichuan Province 总被引:1,自引:0,他引:1
By measuring the Sm-Nd and Rb-Sr isotopic compositions of harzburgite and gabbro from Shimian ophiolite suite, we got the whole rock Sm-Nd isochron age of (938±30) Ma (2?), and the ??Nd of 7.6±0.8 (2?), which shows that the ophiolite was formed at the Early Neoproterozoic. The obvious change (0.70209-0.70708) of ISr values of the ophiolite is caused by the meteoric hydrothermal alteration. The high ? Nd values indicate that the primitive magma was derived from the intense depleted mantle reservoir. It is suggested that this area was in a back-arc basin environment during the Early Neoproterozic. 相似文献
6.
A Sm_Nd age of (228±42) Ma with initial ε Nd =-16.4 for the Renjiawan pyroxenite intrusion in the North Dabie terrane is reported. This age with another Sm_Nd age of (230±44) Ma for the Zhujiapu pyroxenite in the same terrane documents that the pyroxenite in the North Dabie terrane are formed during continental subduction time of the Yangtze craton in the Triassic. 相似文献
7.
8.
Through studying geo-geochemical characteristics and determining Sm-Nd and Rb-Sr isotopical ages in the Kanggur magnetite-chlorite
formation gold deposit, some conclusions can be achieved: Sm-Nd isochron age is (290.4 ± 7)Ma, Rb-Sr isochron age is (282.3
± 5)Ma, mineralization is Late Hercynian and the formation of this gold deposit is related to the macroscopic Huangshan-Qiugemingtashi
ductile shear zone which is produced as a result of collision between the Tarim plate and the Junggar plate. 相似文献
9.
《科学通报(英文版)》1994,39(16):1378-1378
10.
Sm-Nd age dating of high-pressure granulites and amphibolite from Sanggan area, North China craton 总被引:4,自引:0,他引:4
The high pressure (HP) metamorphic age has been dated to HP rocks from the Sanggan area, North China craton. We have got garnet+whole rock isochron ages of (1 842±38) Ma for HP granulite, and (1 856 ± 26) Ma for HP amphibolite. The Sm-Nd whole rock isochron of HP granulites give out an age of (1 870±150) Ma with Nd depleted mantle model age of (2 402—2 482) Ma. Considering the Nd isotope homogenization during the peak metamorphism of the HP granulite, Sm-Nd closure temperature and the retention of Nd isotopic memory in garnets partially broken down during decompression, all these isochron ages are thought to be HP metamorphic age. Furthermore, we proposed that the HP metamorphism took place at the end of Paleoproterozoic during the large-scale collision and assembly of the North China craton. 相似文献
11.
Sm-Nd isotopic age and genesis of gabbro xenoliths in Daoxian County, Hunan Province 总被引:1,自引:0,他引:1
Conclusions The gabbro xenoliths are inferred to form at (224 ± 524) Ma by means of Sm-Nd dating, which reflected the intrusive age or
crystallization age of gabbric melts. This event indicates that the region transformed from stable platform stage into Mesozoic
intensive tectonomagmatic activity stage. The dynamics originated from the upwelling of asthenosphere and lithospheric thinning.
Additionally, according to εNd(T) = + 8.8 ± 0.6 of the gabbro xenoliths, within εNd variation of the MORB at 224 Ma, we know that the gabbro xenoliths are the outcrops of partial melting of the asthenosphere. 相似文献
12.
Discovery of the Early Proterozoic Basement in the Middle-Lower Reaches of Yangtze River and Its Significance 总被引:3,自引:0,他引:3
《科学通报(英文版)》1994,39(2):135-135
13.
Weixuan Fang Ruizhong Hu Wenchao Su Jiafei Xiao Liang Qi Guohao Jiang 《科学通报(英文版)》2002,47(10):874-880
Emplacement ages of lamproites that comprise lamproite and olivine lamproite in Zhenyuan County, Guizhou Province, China, have been constrained by the whole-rock Sm-Nd and Rb-Sr isochron methods and the whole rock K-Ar method. Intrusive activities of lamproites in the Sinantang area of Zhenyuan County, Guizhou Province, took place during the Late Cambrian, as indicated by the Sm-Nd isochron ages ( t ) = (503 ± 17) (2σ) Ma and by the Rb-Sr isochron ages ( t ) = (501.2 ± 4.6) (2σ) Ma. Intrusive activities of olivine lamproites at the Maping with Ⅱ-type diamond and Xitou in Zhenyuan County, Guizhou Province, took place from the Late Cambrian to the Early Ordovician, as evidenced by the Sm-Nd isochron ages ( t ) = (502 ± 27) (2σ) Ma and by the Rb-Sr isochron age ( t ) = (502 ± 27) (2σ) Ma. This suggests that the upwelling hot materials derived from the deep mantle were emplaced from the Late Cambrian to the Early Ordovician (503-497 Ma), while the time terminal of cooling of the geothermal event of magmatism-tectonism probably was at 442.64-435.54 Ma, as dated by the whole rock K-Ar method. 相似文献
14.
The Dongcaohe ophiolite from the North Qilian Mountains: A fossil oceanic crust of the Paleo-Qilian ocean 总被引:9,自引:0,他引:9
Chien-Yuan TSENG Huai-Jen YANG Houng-Yi YANG LIU DunYi Ching-Lang TSAI WU HanQuan ZUO GuoChao 《科学通报(英文版)》2007,52(17):2390-2401
The Dongcaohe ophiolite, located at the south of the North Qilian subduction complexes, is a tectonic block with an exposed area of about 3 km×6 km. It consists of an intrusive section overlain by an ex- trusive section. The lower part of the intrusive section consists of cyclic layers of cumulate dunites, troctolites, anorthosites, anorthositic gabbros, and gabbros with small discordant dunite and troctolite bodies. This layered sequence grades upward to isotropic gabbros and gabbronorites, which are overlain by the extrusive sequence of diabasic sheeted dikes and basaltic lavas. The overall mineral crystallization sequence was olivine±Cr-spinel, plagioclase, clinopyroxene, orthopyroxene, and Fe-Ti oxides. The Cr-spinel (Mg#: 42-66, Cr#: 41-57) in these layered cumulates and present-day abyssal peridotites have similar compositions. Also, the compositional variations of the plagioclase and cli- nopyroxene in the intrusive section reflect crystallization from melts compositionally similar to the present-day ocean basalts. Moreover, the rare earth element (REE) and multi-element distribution pat- terns of the intrusive and extrusive lithologies in the Dongcaohe ophiolite are consistent with crystal- lization of mid-ocean ridge basalts. The zircon grains separated from the gabbronorite have an SHRIMP average 206Pb/238U weighted age of 497 ± 7 Ma, which is considered as the tectonic emplacement age of the Dongcaohe ophiolite. The field occurrence, mineral and whole-rock compositions indicate that the Dongcaohe ophiolite represents a well-persevered oceanic crustal fragment composed of a complete oceanic crustal section of layered cumulates at bottom upgrading through isotropic cumulates to sheeted dikes and lava flows. 相似文献
15.
The Rb-Sr isochron of ore and pyrite sub-samples from Linglong gold deposit, Jiaodong Peninsula, eastern China and their geological significance 总被引:9,自引:1,他引:8
Here we report the first direct Rb-Sr dating of pyrites and ores using sub-sampling from lode gold deposits in Linglong, Jiaodong
Peninsula, which is a supra-large lode gold deposit and propose this as a useful geochronological technique for gold mineralization
with poor age constraint. The Rb-Sr data of pyrites yield an isochron age of (121.6±8.1) Ma, whereas those of ore and ore-pyrite
spread in two ranges from 120.0 to 121.8 Ma and from 110.0 to 111.7 Ma. Studies of characteristic of gold deposit and microscopy
of pyrite and quartz indicate that the apparent ages of ore and ore-pyrite are not isochron ages, only mixed by two end members,
i.e. the primitive hydrothermal fluids and wall rocks, whereas the isochron age of pyrite sub-samples constrains the age of
gold mineralization (121.6±8.1) Ma, i.e. early Cretaceous, which is in good agreement with the published SHRIMP zircon U-Pb
ages. 相似文献
16.
Discovery of Ordovician acritarchs in Buqingshan ophiolite complex, East Kunlun Mountains and its significance 总被引:1,自引:0,他引:1
Qiantao Bian Leiming Yin Shufen Sun Xiaoquan Luo I. Pospelov O. Astrakhantsev N. Chamov 《科学通报(英文版)》2001,46(4):341-345
This note reports the first discovery of Middle-Late Ordovician acritarchs from the Buqingshan ophiolite complex of the southern ophiolite zone of East Kunlun. The acritarch assemblage is dominated with acanthomorphids (approx. 32%) and sphaeromorphds (approx. 63%) and contains more characteristic forms, such as Lophosphaeridium edenense, L. varum, Nothooidium sp.,? Buedingiisphaaeridium sp., Visbysphaera sp., Strophomorpha sp., etc. In addition, some tube-like fragments and tetrads, which are recognized as affinity to terrestrial plants and usual occurrence in Late Ordovician-Early Silurian strata, are preserved together with acritarchs. All the known fossil evidence indicates that the strata should be Middle-Late Ordovician in age. It not only provides paleontological proof for the existence of Ordovician ophiolite, but also challenges the usual ideas on strata composition of the studied area and the southern ophiolite zone of East Kunlun, and the models on tectonic framework and evolution of this area and the northern part of the Qinghai-Tibetan Plateau. 相似文献
17.
Forming age and tectono-petrogenises of the Jiugequan ophiolite in the North Qilian Mountain, NW China 总被引:11,自引:0,他引:11
The Jiugequan ophiolite is one of the representative ophiolite fragments in the Early Paleozoic orogenic belt of the North Qilian Mountain. It has been drawn much attention and extensively studied in recent years. In this study, ion microprobe (SHRIMP) U-Pb dating was carried out for zircons from isotropic gabbro from the Jiugequan ophiolite. Eighteen analyses yield a relatively consistent apparent 206Pb/238U ages from 480 to 508 Ma with a weighted mean age of 490±5 Ma (MSWD=1.06), which is believed to be the crystallization age of the gabbro and thus the forming age of the Jiugequan ophiolite. Major and trace element geochemical study indicates that the diabase-basalts from the Jiugequan ophiolite have N-MORB and E-MORB characteristics with some subduction-related signatures. The petrological, geochemical and chronological data enable us to conclude that the Jiugequan ophiolite is most likely to be formed at a spreading center of back-arc basin during the early Ordovician, while the ancient Qilian oceanic plate subducted northwards. The acquisition of forming age and determination of tectonic setting for Jiugequan ophiolite provide significant constraints on the evolution of intra-oceanic subduction system in the North Qilian orogenic belt during the Early Paleozoic era. 相似文献
18.
Laser micro area analysis 40 Ar 39 Ar isochron dating for pure alunite is first reported. Micro area 40 Ar 39 Ar isochron dating results revealed that the metallogenetic epoch of Fanshan superlarge alunite deposit is 74.50 Ma, and this age is 10-20 Ma later than that of regional volcanic activity. Moreover, the potential application of micro area analysis 40 Ar 39 Ar isochron dating method in metallogenetic epoch studies for nonmetal deposits is also discussed. 相似文献
19.
The total PGE amounts of mantle peridotites in the Dazhuka ophiolite, Tibet, are 28.37—50.67 ng/g, slightly higher than those of mantle peridotites in the primitive mantle, and typical ophiolites in the world, and the Alps-type mantle peridotites. The PGE distribution patterns in the Dazhuka mantle peridotites are also different from those of the mantle peridotites of partial melting relict origin. The Dazhuka mantle peridotites have relatively high total PGE amounts and are enriched in Pt, Pd, and Ru. Their PGE distribution patterns belong to the positively inclined- or swallow-type patterns. The PGE distribution patterns in the mantle peridotites of partial melting relict origin belong to the negative-slope patterns or flat patterns. This reflects the unique features of the upper mantle in this region. Relative enrichment in Pt and Pd, as well as in the incompatible elements Cu, Au, Cs, Rb, Ba, Th, U and LREE, indicates that the partial melting-derived relict mantle peridotites in the Dazhuka ophiolite had experienced intensive permeating and mixing processes of the melt and fluid both containing abundant incompatible elements. 相似文献
20.
An Sm-Nd isotopic dating study of the Archean Kongling Complex in the Huangling area of the Yangtze Craton 总被引:2,自引:0,他引:2
Sm Nd isotopic compositions of associated amphibolites, TTG gneisses and granitic gneisses from the Archean Kongling Complex of the Yangtze Craton, South China are systematically analyzed. The results show that the amphibolites and TTG gneisses have a similar age of ca. 2 700 Ma, which well agrees with zircon U Pb dating of previous studies. However, their ε Nd ( t ) are different, suggestive of possible dissimilarity in source composition. 相似文献