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Chinese Continental Scientific Drilling Project (chinese + continental_scientific_drilling_project)

Distribution by Scientific Domains

Earth and Environmental Science	100%

Selected Abstracts

Fluid Geoanalysis in the Chinese Continental Scientific Drilling Project

GEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2004
Liqiang Luo
fluides; géochimie; analyse en ligne; analyse in situ; forage scientifique continental chinois Mass spectrometry and chromatography were used in the on-line and in situ analysis of fluids in the Chinese continental scientific drilling project. The drilling processes and mud have great effects on the identification of fluids. After considering the effects of air components and artefacts on the deep fluids, we have found that in some segments, helium, methane and carbon dioxide are the main gas components that should originate from the deep Earth. The correlations among gas components are discussed and the fluid profiles in the hole are presented. La spectrométrie de masse et la chromatographie ont été utilisées pour l'analyse in situ et en ligne de fluides dans le cadre d'un projet scientifique de forage continental chinois. Les techniques de forage et la boue ont des effets importants sur l'identification des fluides. Après avoir étudié les effets liés aux composants de l'air et les artefacts dans les fluides profonds, nous avons découvert que, dans certains segments, l'hélium, le méthane et le gaz carbonique étaient les gaz principaux dont l'origine était profonde. Les corrélations entre les composants gazeux sont discutées et les profils des fluides dans le forage sont présentés. [source]

Ultrahigh-pressure metamorphic records hidden in zircons from amphibolites in Sulu Terrane, eastern China

ISLAND ARC, Issue 3 2003
Fulai Liu
Abstract The amphibolites occur sporadically as thin layers and blocks throughout the Sulu Terrane, eastern China. All analyzed amphibolite from outcrop and drill cores from prepilot drill hole CCSD-PP1 and CCSD-PP2, Chinese Continental Scientific Drilling Project in the Sulu Terrane, are retrograded eclogites overprinted by amphibolite-facies retrograde metamorphism, with characteristic mineral assemblages of amphibole + plagioclase + epidote ± quartz ± biotite ± ilmenite ± titanite. However, coesite and coesite-bearing ultrahigh-pressure (UHP) mineral assemblages are identified by Raman spectroscopy and electron microprobe analysis as inclusions in zircons separated from these amphibolites. In general, coesite and other UHP mineral inclusions are preserved in the cores and mantles of zircons, whereas quartz inclusions occur in the rims of the same zircons. The UHP mineral assemblages consist mainly of coesite + garnet + omphacite + rutile, coesite + garnet + omphacite, coesite + garnet + omphacite + phengite + rutile + apatite, coesite + omphacite + rutile and coesite + magnesite. Compositions of analyzed mineral inclusions are very similar to those of matrix minerals from Sulu eclogites. These UHP mineral inclusion assemblages yield temperatures of 631,780°C and pressures of ,2.8 × 103 MPa, representing the P,T conditions of peak metamorphism of these rocks, which are consistent with those (T = 642,726°C; P , 2.8 × 103 MPa) deduced from adjacent eclogites. These data indicate that the amphibolites are the retrogressive products of UHP eclogites. [source]

Ultrahigh-pressure and Retrograde Metamorphic Ages for Paleozoic Protolith of Paragneiss in the Main Drill Hole of the Chinese Continental Scientific Drilling Project (CCSD-MH), SW Sulu UHP Terrane

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2006
LIU Fulai
Abstract, Laser Raman spectroscopy and cathodoluminescence (CL) images show that most zircon crystals separated from paragneiss in the main drill hole of the Chinese Continental Scientific Drilling Project (CCSD-MH) at Maobei, southwestern Sulu terrane, contain low-pressure mineral-bearing detrital cores, coesite-bearing mantles and quartz-bearing or mineral inclusion-free rims. SHRIMP U-Pb dating on these zoned zircons yield three discrete and meaningful age groups. The detrital cores yield a large age span from 659 to 313 Ma, indicating the protolith age for the analyzed paragneiss is Paleozoic rather than Proterozoic. The coesite-bearing mantles yield a weighted mean age of 228 ± 5 Ma for the UHP event. The quartz-bearing outmost rims yield a weighted mean age of 213 ± 6 Ma for the retrogressive event related to the regional amphibolite facies metamorphism in the Sulu UHP terrane. Combined with previous SHRIMP U-Pb dating results from orthogneiss in CCSD-MH, it is suggested that both Neoproterozoic granitic protolith and Paleozoic sedimentary rocks were subducted to mantle depths in the Late Triassic. About 15 million years later, the Sulu UHP metamorphic rocks were exhumed to mid-crustal levels and overprinted by an amphibolite-facies retrogressive metamorphism. The exhumation rate deduced from the SHRIMP data and metamorphic P-T conditions is about 6.7 km/Ma. Such a fast exhumation suggests that the Sulu UHP paragneiss and orthogneiss returned towards the surface as a dominant part of a buoyant sliver, caused as a consequence of slab breakoff. [source]

Zircon U,Pb age and Hf isotope evidence for contrasting origin of bimodal protoliths for ultrahigh-pressure metamorphic rocks from the Chinese Continental Scientific Drilling project

JOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2007
R.-X. CHEN
Abstract A combined study of zircon morphology, U,Pb ages and Hf isotopes as well as whole-rock major and trace elements was carried out for ultrahigh-pressure (UHP) eclogite and felsic gneiss from the main hole (MH) of the Chinese Continental Scientific Drilling (CCSD) project in the Sulu orogen. The results show contrasting Hf isotope compositions for bimodal UHP metaigneous rocks, pointing to contrasting origins for their protoliths (thus dual-bimodal compositions). The samples of interest were from two continuous core segments from CCSD MH at depths of 734.21,737.16 m (I) and 929.67,932.86 m (II) respectively. Zircon U,Pb dating for four samples from the two core segments yields two groups of ages at 784 ± 17 and 222 ± 3 Ma, respectively, corresponding to protolith formation during supercontinental rifting and metamorphic growth during continental collision. Although the Triassic UHP metamorphism significantly reset the zircon U,Pb system of UHP rocks, the Hf isotope compositions of igneous zircon can be used to trace their protolith origin. Contrasting types of initial Hf isotope ratios are, respectively, correlated with segments I and II, regardless of their lithochemistry. The first type shows positive ,Hf(t) values of 7.8 ± 3.1 to 6.0 ± 3.0, with young Hf model age of 1.03 and 1.11 Ga. The second type exhibits negative ,Hf(t) values of ,6.9 ± 1.6 to ,9.1 ± 1.1, with old Hf model ages of 2.11 and 2.25 Ga. It appears that the UHP rocks from the two segments have protoliths of contrasting origin. Consistent results are also obtained from their trace element compositions suggesting that mid-Neoproterozoic protoliths of bimodal UHP metaigneous rocks formed during supercontinental rifting at the northern margin of the South China Block. Thus, the first type of bimodal magmatism formed by rapid reworking of juvenile crust, whereas the second type of bimodal magmatism was principally generated by rift anatexis of Paleoproterozoic crust. Melting of orogenic lithosphere has potential to bring about bimodal magmatism with contrasting origins. Because arc,continent collision zones are the best place to accumulate both juvenile and ancient crusts, the contrasting types of bimodal magmatism are proposed to occur in an arc,continent collision orogen during the supercontinental rifting, in response to the attempted breakup of the supercontinent Rodinia at c. 780 Ma. [source]