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411.
Shengyi Mao Hongxiang Guan Lihua Liu Xiqiu Han Xueping Chen Juan Yu Yongge Sun Yejian Wang 《海洋学报(英文版)》2021,40(8):53-64
Hydrothermal venting has a profound effect on the chemical and biological properties of local and distal seawater and sediments. In this study, lipid biomarkers were analyzed to examine the potential influence of hydrothermal activity on the fate of organic matter(OM) in surface sediments around Tianxiu Hydrothermal Field in the Carlsberg Ridge(CR), Northwest Indian Ocean. By comparing the biomarker distributions of the samples with that of other typical hydrothermal sediments in the mid ocean ridge, it is shown that the location of the samples is not affected by the hydrothermal activity. The relatively low abundances of terrestrial n-alkyl lipids and riverine1,15-C32 diol suggested a minor contribution of terrigenous OM to the study area. The bacteria contributed predominantly to sedimentary marine OM; however, other marine source organisms, e.g., eukaryotes(i.e.,phytoplankton and fungi) could not be completely neglected. The marine-originated biomarkers showed significantly variable distributions between the two sediments, suggesting different dynamic physical and biogeochemical processes controlling the fate of marine OM. This study identified various diagnostic biomarkers(5,5-diethyl alkanes, diols and β-OH FAs), which may have significant environmental implications for future works in this region. 相似文献
412.
M. J. Bartholomew 《Geological Journal》1983,18(3):241-253
Examinations of Grenville massifs in the Blue Ridge Geologic Province of Virginia and North Carolina indicate that the country rocks (∼ 1100–1450 Ma) are layered gneisses that were metamorphosed during Grenville orogenesis (∼ 1000–1100 Ma) to amphibolite to granulite facies and intruded by plutonic suites. Subsequently, the Grenville terrane was intruded by a suite of peralkaline granitic plutons (∼ 700 Ma) and progressively overlapped westward by Upper Precambrian to Cambrian sedimentary and volcanic rocks. Following deposition of Upper Precambrian and Palaeozoic rocks, the Blue Ridge Geologic Province was subjected to Taconic metamorphism (∼ 450–480 Ma) which generally increased in intensity southeastward from greenschist (chlorite grade) to upper amphibolite (sillimanite grade) facies. Large-scale late Devonian thrusting (∼ 350 Ma) along the Fries fault system and the Brevard zone-Yadkin fault system produced the present day distribution of juxtaposed Grenville massifs and Palaeozoic metamorphic zones in the Blue Ridge Geologic Province. Palinspastic restoration of the Taconic metamorphic zones to their pre-late Devonian relative positions yields an ∼ 50 km displacement on the Fries fault system near the Grandfather Mountain window and and an ∼ 80 km displacement on the Smith River allochthon farther east. Restoration of the Grenville massifs to this same palinspastic base shows that Grenville metamorphic grade decreased southeastward from the deeper granulite facies (opx + gar) to the shallower granulite facies (opx ± amp) to amphibolite facies. 相似文献
413.