New high-resolution 2D seismic imaging of fluid escape structures in the Makran subduction zone,Arabian Sea     

《China Geology》2020,3(2):269-282

Seabed fluid escape is active in the Makran subduction zone, Arabian Sea. Based on the new high-resolution 2D seismic data, acoustic blanking zones and seafloor mounds are identified. Acoustic blanking zones include three kinds of geometries: Bell-shaped, vertically columnar and tilted zones. The bell-shaped blanking zone is characterized by weak and discontinuous reflections in the interior and up-bending reflections on the top, interpreted as gas chimneys. Vertically columnar blanking zone is interpreted as side-imaged gas chimneys associated with focused fluid flow and topped by a seafloor anomaly expressed as a localized reflection discontinuity, which may together serve as a vent structure. Tilted acoustic blanking zone could be induced by accretionary thrust activity and rapid sedimentation surrounding slope. Seafloor mounds occur at the sites of bell-shaped acoustic blanking zone and may be associated with the material intrusion. Bottom simulating refectors (BSRs) are widely distributed and exhibit a series of characteristics including diminished amplitude, low continuity as well as local shoaling overlapping with these acoustic blanking zones. The large amount of gases dissociated from the gas hydrates migrated upwards and then arrived at the near-seafloor sediments, followed by the formation of the gas hydrates and hence the seafloor mound.  相似文献   

川西甲基卡矿床外围中酸性侵入岩LA-ICP-MS锆石U-Pb年龄及地球化学特征     

李名则  秦宇龙  赵春  詹涵钰  周雄  孙光银 《中国地质调查》2020,7(5):1-9

在川西甲基卡矿床外围新发现了建巴村中酸性侵入岩体,为了探讨其形成时代、成岩构造背景及其成矿条件,开展了LA-ICP-MC锆石U-Pb年代学和地球化学特征研究。结果表明: 该岩体的结晶年龄为(211.8±1.0) Ma; 岩石属于钙碱性-高钾钙碱性准铝质中酸性侵入岩系列,具有I型花岗岩类的特征,其物质来源可能为壳源物质与幔源物质部分熔融。地球化学特征表明其形成于后碰撞环境,与此时期内川西地区的区域性岩浆活动相对应。建巴村岩体的构造位置及岩浆活动特征指示其可能不具备形成伟晶岩矿床的条件。  相似文献   

Using Models of the Deep Structure of the Earth’s Crust and Upper Mantle Based on GOCE Gravity Data in Metallogenic Analysis     

Volkov  A. V.  Galyamov  A. L.  Savchuk  Yu. S. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1528-1536

Izvestiya, Atmospheric and Oceanic Physics - Gravimetric data obtained by the GOCE spacecraft contributes to the development of global models of the deep structure of the Earth’s crust and...  相似文献   

Capillary End Effects in Reservoirs with Heterogeneous Wettability     

Mikhailov  N. N.  Ermilov  O. M.  Mikhailov  A. N. 《Doklady Earth Sciences》2020,494(1):680-683

Doklady Earth Sciences - A new type of capillary end effect in oil and gas reservoirs due to heterogeneous wettability has been justified. This type of capillary end effect is not related to the...  相似文献   

Zircon provenances provide paleogeographic constraints on models reconstructing the Paleoproterozoic Columbia Supercontinent     

《Gondwana Research》2020

Paleoproterozoic orogens of the North Australian Craton are related to the assembly of the Columbia Supercontinent. The roles of the distinct orogens in the Paleoproterozoic craton amalgamation are poorly understood due to the lack of surface exposure. The age and isotopic systematics of detrital zircon grains hosted in Paleoproterozoic sedimentary sequences are used to unravel the geological history of the craton, in terms of paleogeography and tectonic setting. The oldest (Early Paleoproterozoic) metasedimentary units are characterised by detrital zircon ages peaking at ca. 2500 Ma. The zircon ε_Hf values show large variations in the different orogens and range from −18 to +6. The overlaying youngest turbiditic units show minor accumulation of Archean detritus. Units from apparently different metasedimentary sequences have a major detrital zircon age population at ca. 1865 Ma, and a relatively restricted range of zircon ε_Hf values between −7.3 and +2.6. The isotopic distinctiveness of the oldest units is attributed to local variations in the depositional environment, probably due to horst-graben architecture of the early Paleoproterozoic basin. The youngest turbiditic units blanketed this early horst-graben architecture and in part have a local provenance. Potential detritus sources include South Australian Craton, Dharwar Craton and Aravalli-Lesser Himalayan terrains in India, South China, and Madagascar (Africa). This finding indicates that these regions might have been connected before the Columbia Supercontinent was formed. The ubiquitous ca. 2500 Ma magmatic event records the assembly of these cratonic fragments in a previous supercontinent called Kernorland. In addition, the data do not support a proximity of the North Australian Craton with the North China Block, Western Laurentia (North America), and Kaapvaal Craton (Africa) during Columbia amalgamation.  相似文献   

Stable climate in India during Deccan volcanism suggests limited influence on K–Pg extinction     

《Gondwana Research》2020

Large igneous provinces (LIPs) have been temporally correlated to mass extinctions throughout the Phanerozoic, including the emplacement of the Deccan Volcanic Province (DVP; 66.3–65.6 Ma) in western and central India, which has been invoked as either a cause or exacerbating factor in the Cretaceous-Paleogene (K-Pg) extinction. However, relatively little is known about local paleoclimatic and paleoenvironmental responses to volcanism. To investigate the DVP's role as a driver of local environmental change and to provide climatic background for known ecological shifts, new inter-basaltic paleosol profiles at the eastern edge of the DVP are used in conjunction with profiles from the literature to reconstruct paleoclimate and terrestrial environments before and after the K–Pg. These profiles provide a novel opportunity to study the sediments within basalt flows before, during, and after a mass extinction event and in the midst of a LIP emplacement event. Paleoclimate proxies and the Floral Humidity Province proxy reflect little long-term change in either climate or environment across the K–Pg, with stable precipitation values and temperatures accompanied by a constant forest signal. These interpretations are corroborated by macrofloral records and sedimentology from India, which suggest some environmental turnover but generally support a forested, fluvio-lacustrine environment throughout the duration of volcanism. Our results support the possibility of rapid recovery times for terrestrial ecosystems during volcanism and suggest that while DVP eruptions may have exacerbated long-term environmental perturbation, the emplacement of the DVP is not likely to have caused the terrestrial mass extinction at the K–Pg boundary.  相似文献   

Structural Control of Gold Mineralization of the Central Part of the Malouralsky Volcano–Plutonic Belt (the Polar Urals), Based on an Analysis of Multispectral Images from the Landsat 8 Spacecraft     

Ivanova  J. N.  Vyhristenko  R. I.  Vikentyev  I. V. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1537-1545

Izvestiya, Atmospheric and Oceanic Physics - The central part of the Malouralsky volcanic–plutonic belt, which includes the Manyukuyu–Vorchatinsky ore cluster, is analyzed using...  相似文献   

A New Approach to ID-TIMS U–Pb Dating of Cassiterite by the Example of the Pitkäranta Tin Deposit     

Rizvanova  N. G.  Kuznetsov  A. B. 《Doklady Earth Sciences》2020,491(1):146-149

Doklady Earth Sciences - A new technique for the complete dissolution of cassiterite, which makes it possible to determine the age of this mineral by U–Pb isotope dilution (ID-TIMS), has been...  相似文献   

Uranium-Lead and Lu–Hf Isotope Systematics of Zircon and Sm–Nd Isotopes in Rocks of the Dyumtaley Ore-Bearing Intrusion (Taimyr,Russia): New Evidence for the Role of the Depleted Mantle in Its Genesis     

Malitch  K. N.  Lokhov  D. K.  Proskurnin  V. F.  Puchkov  V. N.  Badanina  I. Yu.  Chervyakovskaya  M. A. 《Doklady Earth Sciences》2020,492(1):346-350

Doklady Earth Sciences - This study utilized SHRIMP, LA MC–ICP–MS and ID-TIMS analytical techniques and presents for the first time U–Pb age, Lu-Hf-isotope features of zircon and...  相似文献   

Geochemistry and detrital zircon U–Pb dating of Pliocene-Pleistocene sandstones of the Chittagong Tripura Fold Belt (Bangladesh): Implications for provenance     

《Gondwana Research》2020

The Bengal Basin originated during the collision of India with Eurasia and Burma. The provenance analysis of the Chittagong Tripura Fold Belt (CTFB), which is the folded eastern flank of the Bengal Basin as well as the Neogene belt of the Indo-Burman Ranges (IBR) is key to better understand the possible sources of sediment input from the complex interplay of the Indian, Eurasian and Burma plates. We report new whole rock geochemical and detrital zircon U–Pb data from the upper Neogene sandstones of Tipam-Dupi Tila formations (Pliocene to Plio-Plestocene succession) from the CTFB. Detrital zircon U–Pb age spectra show three predominant peaks at <200 Ma, 480–650, ∼800–1000 Ma. The geochemical discriminations and elemental ratios of Eu/Eu* (∼0.70), La/Sc (∼16.13), La/Co (∼15.76), Th/Sc (∼2.95), La/Th (∼5.67), Th/Co (∼2.87), Cr/Th (∼4.63) as well as Chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies for the Tipam and Dupi Tila formations are suggestive of a dominantly felsic source area experiencing moderate to intensive chemical weathering (Chemical index of alteration, CIA - 57 to 81) and have a recycled provenance orogen related to active continental or passive margin settings. Integrated geochemical and zircon U–Pb studies reveal that the main sediment input might have been from the Himalayan orogen with significant arc-derived detritus, possibly from the Gangdese arc as well as from the Burma magmatic arc.  相似文献