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    International Continental Scientific Drilling Project of the Songliao Basin: Terrestrial Geological Records of the Cretaceous Dinosaur Age
    Earth Science Frontiers    2024, 31 (1): 511-534.   DOI: 10.13745/j.esf.sf.2024.1.4-en
    Abstract1291)   HTML    PDF(pc) (5783KB)(107)       Save

    Over the past century global temperatures continue to rise, and the Earth may enter a greenhouse period in the future with no ice at the poles. The Cretaceous was a typical greenhouse period in deep time, and thus understanding the Cretaceous climate is significant for interpreting past climate changes and predicting future trends. The International Continental Scientific Drilling Project of the Songliao Basin is the world's first continental scientific drilling project to penetrate the Cretaceous continental strata within the framework of the ICDP. This project is aimed to investigate Cretaceous terrestrial climate and environmental changes, and to explore the mechanisms of massive terrestrial organic matter accumulation and enrichment. Spanning 16 years, this project achieves a continuous and complete 8187-meter core with a recovery rate exceeding 97%, establishes a high-precision chronostratigraphic framework for the Cretaceous continental strata in the Songliao Basin, reconstructs multi-temporal-scale terrestrial climate cycles and climate events during the Cretaceous period, reveals the mechanisms of Cretaceous sea-level fluctuations, and confirms marine incursion events in the Songliao Basin. The International Continental Scientific Drilling Project of the Songliao Basin has promoted global collaboration among geologists to study Cretaceous greenhouse climates, leading to a series of high-impact research achievements. It has provided crucial scientific support for the sustainable development of oil and gas exploration in the Songliao Basin, and has generated significant social benefits and substantial international and domestic influence. The International Continental Scientific Drilling Project of the Songliao Basin represents a milestone stage in exploring deep-time Earth, and it is foreseeable that in the future, humans will continue enhancing the understanding of deep-time climate and environmental evolution with the aid of scientific drilling.

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    Enrichment conditions and distribution characteristics of lacustrine medium-to-high maturity shale oil in China
    ZHAO Wenzhi, ZHU Rukai, LIU Wei, BIAN Congsheng, WANG Kun
    Earth Science Frontiers    2023, 30 (1): 242-259.   DOI: 10.13745/j.esf.sf.2022.8.31-en
    Abstract406)   HTML48)    PDF(pc) (1551KB)(106)       Save
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    Deep seismic reflection evidence on the deep processes of tectonic construction of the Tibetan Plateau
    GAO Rui, ZHOU Hui, GUO Xiaoyu, LU Zhanwu, LI Wenhui, WANG Haiyan, LI Hongqiang, XIONG Xiaosong, HUANG Xingfu, XU Xiao
    Earth Science Frontiers    2021, 28 (5): 320-336.   DOI: 10.13745/j.esf.sf.2021.8.10
    Abstract844)   HTML286)    PDF(pc) (14121KB)(876)       Save

    The collision between the Indian and Asian plates uplifted the Himalayan- Tibetan Plateau, thickening and expanding the crust. It is a scientific mystery of global concern as how the two continents collide and how the continent-continent collision deforms the continent. Deep seismic reflection profile detection is one of the most effective ways to unlock this scientific mystery. For more than 20 years using this technology, we have detected fine structures of the thick crust of the Tibetan plateau after overcoming technical bottlenecks to access the lower crust and Moho thus revealing the continental collision processes. This paper systematically summarizes the deep behaviors of the India-Asia collision and subduction beneath the Tibetan Plateau, from south to north, east to west and further into the hinterland of the plateau. The Indian crust undergoes underthrusting beneath the Himalayan orogenic belt on the southern margin of the plateau. Meanwhile, the lithosphere of the Alxa block in the Asian plate subducts southward beneath the Qilian Mountain in the north of the plateau, driving the northward overthrusting of the Qilian crust. Additionally, the Tarim and West Kunlun blocks undergo face-to-face collision in the northwestern margin of the plateau. In the easternmost part of the plateau, the Longriba fault, instead of the Longmen Shan fault zone, marks the western margin of the Yangtze block. It is also seismically evidenced that the Moho geometry in the plateau’s hinterland appears thin and flat, indicating lithospheric collapse and extrusion. Multiple deep reflection profiles revealed the collisional behavior under the Yalung-Zangbo suture zone and longitudinal variation in subducting geometry of the Indian crust from west to the east. In the middle of the suture zone, it shows a decoupling between the upper and lower crusts of the Indian plate, where the upper crust undergoes a northward overthrusting while the lower one experiences a northward underthrusting. It is also seismically evidenced a down-and southward crustal duplexing of the subducting Indian crust thickening the northern Himalayas, leaving over a thinning subducting lower crust of the Indian slab. The subduction front of the Indian crust collides with the lower crust of the Asian plate at the mantle depth. A near-vertical collision boundary is seen between the Gangdese batholith and the Tethyan Himalayas, where the Gangdese batholith shows almost transparent weak reflections in the lower crust with localized bright spot reflection that indicates partial melting. Additionally, the near-flat Moho geometry implies an extensional tectonic environment of the southern margin of the Asian plate.

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    Geological-geophysical models of the Earth’s crust along the Russian-Mongolian geotransects
    Evgeny Kh. TURUTANOV, Evgeny V. SKLYAROV, Valentina V. MORDVINOVA, Anatoly M. MAZUKABZOV, Viktor S. KANAYKIN
    Earth Science Frontiers    2021, 28 (5): 260-282.   DOI: 10.13745/j.esf.sf.2021.3.10
    Abstract1301)   HTML33)    PDF(pc) (7300KB)(315)       Save

    Transects are vertical sections of the Earth’s crust, which reveal the nature of tectonic zones, as well as their spatial relationships through a combined analysis of their geology and geophysics. Transect documents contain a geological map for a strip of land 100 km wide, a geological section of the upper crust, gravity and magnetic maps (and/or corresponding profiles along the transect), and a geophysical profile of the crust, differentiated by seismic velocities, densities and other geophysical properties. These data are used to compose a combined cross-section (the resulting section), which shows a set of rocks typical of various geodynamic conditions (rifts, oceans, collision zones, orogenic basins, continental platforms and magmatic arcs, including Andean island arcs, active continental outskirts, trenches, basins of front and rear arcs). The objective of this project was to build deep sections according to unified legends based on the interpretation of all available geological and geophysical data in order to determine the spatial relationship of terranes and their geodynamic nature in terms of plate tectonics.
    A number of terranes have been discriminated in the territory of the southern part of Eastern Siberia and the territory of Mongolia, and their geodynamic nature and space-time relations were analysed. The terranes were found out to be Vendian-Early Paleozoic, Middle-Late Paleozoic and Late Paleozoic-Early Mesozoic island arcs and microcontinents. Moreover, Middle-Late Paleozoic and Late Paleozoic-Early Mesozoic Andean-type active continental margins and Late Paleozoic-Early Mesozoic passive margins and Early Cretaceous rifts were identified and studied. The rock complexes related to the island arcs and Andean-type active continental margins are thrust over the bordering continents and microcontinents, the width of the respective tectonic nappes attaining 150 km. Schematic paleogeodynamic reconstructions for the area of the Mongolia-Okhotsk ocean have been performed, spanning the period from Devonian to Late Jurassic.
    “Non-geosyncline” granitoid magmatism finds straightforward and sound explanation in terms of plate tectonics where provinces of Devonian-Carboniferous and Permian-Triassic magmatism correspond to Andean-type active continental margins and Middle-Late Jurassic magmatism is associated with Siberia/Mongolia-China collision. The presence of a subalkaline (mantle) element in collisional magmatism and the great extent of the area it occupies can be explained by suggesting that an oceanic rift (a mantle hotspot) was buried under thick continental lithosphere after closure of the Mongolia-Okhotsk ocean. In the Early Cretaceous, the setting of collision gave way to that of continental rifting.
    The existence of an Andean-type active margin over the great extent of the southern border of Siberia is likewise responsible for minor abundance of ophiolites along the Mongolia-Okhotsk suture. When one colliding continent has an Andean-type active margin and the other has a passive margin, the continental crust of the former thrusts over the latter, and no conditions arise for ophiolites to expose. Blocks of dismembered ophiolites, that are remnants of truncated seamounts, can be part of chaotic complexes building accretion-subduction wedges. However, accumulation of such wedges in the Late Permian-Early Jurassic was not typical of the active margin of Siberia because of rapid subduction.
    An analysis of geological and geophysical data on transects shows that the Asian continent was formed in the Phanerozoic as a result of accretion of terranes, some of which were microcontinents with a Precambrian foundation. Precambrian blocks are separated by deformed and strongly eroded Phanerozoic igneous arcs of various widths, also classified as specific terranes.

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    Natural mineral photoelectric effect: mineral non-classical photosynthesis
    LU Anhuai, LI Yan, DING Hongrui, WANG Changqiu, XU Xiaoming, LIU Feifei, LIU Yuw
    Earth Science Frontiers    2020, 27 (5): 300-.   DOI: 10.13745/j.esf.sf.2020.12.3
    Abstract511)      PDF(pc) (1024KB)(261)       Save
    Under the ever-present solar radiation, photosynthetic organisms on Earth evolved structurally-sophisticated photosynthetic systems. However, little attention has been paid to the inherent impact of sunlight illumination on the inorganic minerals widespread on the Earth surface. We discovered for the first time the solar energy conversion system of the “mineral coatings” on the Earth's surface (aka “mineral membrane”), which exerts potential oxygen-production and carbon-sequestration functions on the Earth surface. Our finding shed a light on the photoelectric effect and non-classical photosynthesis involving natural semiconducting minerals. In this contribution, we studied the semiconducting property and photoelectron energy of typical minerals in the “mineral membrane”, focusing primarily on the photoelectric effect in and oxygen-production/carbon-sequestration function of ferromanganese oxides, as well as relevant geological records. We propose that birnessite, goethite and hematite, the semiconducting minerals commonly found in the “mineral membrane”, can perform sensitive and stable photon-to-electron conversion under solar radiation.  The non-classical mineral photosynthetic function we put forth is as follows: Solar energy utilization by inorganic minerals resembles photosynthesis in regarding to oxygen evolution and carbon fixing, and the “mineral membrane” may take part in both photocatalytic water-oxidation reaction and transformation of atmospheric CO2 into marine carbonate. In addition, minerals might as well have promoted photosynthesis in photosynthetic organisms. During the water-oxidation reaction, the inorganic cluster Mn4CaO5 of photosystem II cycles through redox intermediates that are analogous to birnessite both in structure and component. Thus, it is fair to postulate that birnessites could play a role in the initiation of the photosynthesis in cyanobacteria, as minerals could weaken the hydrogen bond strength and alter water properties, thus facilitating water oxidation and photosynthesis. This observation offers further insights into the molecular mechanism of mineral participation in photosynthesis in photosynthetic organisms.
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    Core value of the Chengjiang fauna: formation of the animal kingdom and the birth of basic human organs
    SHU Degan, HAN Jian
    Earth Science Frontiers    2020, 27 (6): 382-412.   DOI: 10.13745/j.esf.sf.2020.10.28
    Abstract1030)   HTML852)    PDF(pc) (25271KB)(345)       Save
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