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China Geology 2023年第4期6卷 751-752页

作者： Cheng-long Wang Li-bin Song Hong-qi Yuan School of Earth Sciences Northeast Petroleum UniversityDaqing 163318China Exploration and Development Institute of PetroChina Jilin Oilfield Company Songyuan 138000China

1. Objective The Songliao Basin is a superposed basin filled with two layers. The lower layer is characterized by a fault-bounded volcanogenic succession comprising of intercalated volcanic,pyroclastic and epiclastic rocks. The upper layer is composed of normal sedimentary rocks. The Huoshiling Formation is the earliest volcanic stratum in the Songliao Basin. The report of geological age of it was rare, because of the lack of credible dating samples.

关键词： volcanic Songliao rock

Strong link between large tropical volcanic eruptions and severe droughts prior to monsoon in the central Himalayas revealed by tree-ring records

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Science Bulletin 2019年第14期64卷 1018-1023页

作者： Eryuan Liang Binod Dawadi Neil Pederson Shilong Piao Haifeng Zhu Shalik Ram Sigdel Deliang Chen Key Laboratory of Alpine Ecology Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100101 China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of Sciences Beijing 100101 China Central Department of Hydrology and Meteorology Tribhuvan University Kathmandu Nepal Harvard Forest Harvard University Petersham MA 01366 USA College of Urban and Environmental Sciences Peking University Beijing 100871 China Key Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100101 China Regional Climate Group Department of Earth Sciences University of Gothenburg Gothenburg 40530 Sweden

Large tropical volcanic eruptions can cause short-term global cooling. However, little is known whether large tropical volcanic eruptions, like the one in Tambora/Indonesia in 1815, cause regional hydroclimatic anomalies. Using a tree-ring network of precisely dated Himalayan birch in the central Himalayas, we reconstructed variations in the regional pre-monsoon precipitation back to 1650 CE. A superposed epoch analysis indicates that the pre-monsoon regional droughts are associated with large tropical volcanic eruptions, appearing to have a strong influence on hydroclimatic conditions in the central Himalayas. In fact, the most severe drought since 1650 CE occurred after the Tambora eruption. These results suggest that dry conditions prior to monsoon in the central Himalayas were associated with explosive tropical volcanism. Prolonged La Ni?a events also correspond with persistent pre-monsoon droughts in the central Himalayas. Our results provide evidence that large tropical volcanic eruptions most likely induced severe droughts prior to monsoon in the central Himalayas.

关键词： Tree ring Drought Tropical volcanic eruptions Central Himalayas

Zircon SHRIMP U–Pb age of Late Jurassic OIB-type volcanic rocks from the Tethyan Himalaya: constraints on the initial activity time of the Kerguelen mantle plume

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Acta Geochimica 2018年第3期37卷 441-455页

作者： Yuruo Shi Chenyang Hou J. Lawford Anderson Tianshui Yang Yiming Ma Weiwei Bian Jingjie Jin Beijing SHRIMP Center Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China China University of Geosciences Beijing 100083 China Department of Earth and Environment Boston UniversityBoston MA 02215 USA

This work presents zircon U–Pb age and wholerock geochemical data for the volcanic rocks from the Lakang Formation in the southeastern Tethyan Himalaya and represents the initial activity of the Kerguelen mantle plume. SHRIMP U–Pb dating of zircons from the volcanic rocks yielded a ^(206) Pb/^(238) U age of 147 ± 2 Ma that reflects the time of Late Jurassic magmatism. Whole rock analyses of major and trace elements show that the volcanic rocks are characterized by high content of Ti O_2(2.62 wt%–4.25 wt%) and P_2O_5(0.38 wt%–0.68 wt%), highly fractionated in LREE/HREE [(La/Yb)N= 5.35–8.31] with no obvious anomaly of Eu, and HFSE enrichment with no obvious anomaly of Nb and Ta, which are similar to those of ocean island basalts and tholeiitic basaltic andesites indicating a mantle plume origin. The Kerguelen mantle plume produced a massive amount of magmatic rocks from Early Cretaceous to the present, which widely dispersed from their original localities of emplacement due to the changing motions of the Antarctic, Australian, and Indian plates. However, our new geochronological and geochemical results indicate that the Kerguelen mantle plume started from the Late Jurassic. Furthermore, we suggest that the Kerguelen mantle plume may played a significant role in the breakup of eastern Gondwanaland according to the available geochronological, geochemical and paleomagnetic data.

关键词： volcanic rocks Late Jurassic ZirconSHRIMP U-Pb age Kerguelen mantle plume TethyanHimalaya Lakang Formation

Depositional model of Permian Luodianian volcanic island and its impact on the distribution of fusulinid assemblage in southern Qinghai,Northwest China

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Science China Earth Sciences 2008年第4期51卷 594-607页

作者： NIU ZhiJun XU AnWu WANG JianXiong DUAN QiFa ZHAO XiaoMing YAO HuaZhou Yichang Institute of Geology and Mineral Resources China Geological SurveyYichang 443003China

Pan-riftizational tectonic activity reached climax at Luodianian (Permian) in the East Tethyan Domain, Qinghai-Tibet Plateau. Because of eruptive volcanics and influence of terrigenous materials, a complex volcanic-sedimentary landform formed on the sea floor in southern Qinghai. Four sedimentary facies types were recognized based on detailed field mapping. Spatially, platform facies volcanic-limestone type was located at the center belt approximately trending NWW, surrounded by shallow water slope facies tuff/tuffite type at the two flanks and deep water slope facies breccia/calcirudite at the most outside. The depression facies sandstone-mudstone type, which comprised mainly mudstone, de-posited between volcanic islands (platform facies volcanic-limestone type). Based on the field map-ping and stratigraphic section data, seven rift-related sedimentary facies were recognized and a depo-sitional model for volcanic island was proposed. It is revealed that some volcanic island chain formed quickly and intermittently in the Qamdo Block during violent eruption, and small carbonate reef, shoal, platform occurred above or on edge of volcanic island, and some slope sedimentary facies surrounded volcano island chain during dormant period of volcanic activities. Three types of fusulinid assemblages were distinguished in the carbonate rocks, which deposited in varied positions of a palaeo-volcanic island: (1) Misellina-Schwagerina assemblage occurred above or on edge of volcanic island, (2) Para-fusulina assemblage was located at restricted depression facies among volcanic islands or carbonate platform, and (3) the reworked Pseudofusulina-Schwagerina assemblage occurred at slope facies near margin of volcanic island, which originally deposited in the shallow-water carbonate platform, then collapsed along the volcanic island margin with fusulinid-bearing grain-supported carbonate con-glomerate or calcirudite, and finally re-deposited on the deeper slope. The sedimentary sequence re-sulting from calm shallow water was deposi

关键词： volcanic rocks sedimentary facies depositional model fusulinid Permian Qinghai

Zircon U-Pb dating on the Mesozoic volcanic suite from the Qingshan Group stratotype section in eastern Shandong Province and its tectonic significance

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Science China Earth Sciences 2007年第6期50卷 813-824页

作者： LING WenLi XIE XianJun LIU XiaoMing CHENG JianPing Faculty of Earth Sciences China University of GeosciencesWuhan 430074China State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan 430074China Key Laboratory of Continental Dynamics Northwest UniversityXi’an 710069China

A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the method of in situ ablation of a 193 nm excimer laser system coupled with an up to date ICP-MS system. Among the three formations of the Qingshan Group, zircons recovered from the lowest part of the Houkuang Fm. were dated at 106±2 Ma (95% confidence, the same below), whereas those from the lower and upper parts of the Shiqianzhuang Fm. were given ages of 105±4 Ma and 98±1 Ma, respectively. A spatially decreasing trend for the Mesozoic magmatic timing from west to east in the province is observed through comparing the data of this study with those by previous works on the Qingshan volcanic lavas occurring at western Shandong and within the Yishu fault zone. The Qingshan volcanic rocks are constituent of the 'Shoshonite Province' in East China. Exposed at most provinces of central East China along the Tan-Lu fault and the Yangtze fault zones, these volcanic suites are characterized by shoshonite and high-K calcalkalic rocks in lithology and thought to be correlated with the partial melting of continental mantle in genesis. It is also shown that the Qingshan potassic volcanic suite from eastern Shandong basins is distinctly younger than those from other ar-eas of the shoshonite province. By contrary, ages of the Mesozoic to Cenozoic alkaline basalts, sourced by asthenospheric mantle, from both northern Huaiyan basin and northern Dabie belt along the Tan-Lu fault zone and from the Ningwu, Lishui and Luzong basins along the Yangtze fault zone are observably older than those occurring within eastern Shandong. The revealed temporal and spatial patterns in magmatism for the two types of volcanic suites make an important geochronological con-straint on the Mesozoic to Cenozoic dynamic evolution model of the subcontinental lithosphere in East China.

关键词： Mesozoic volcanic suite Qingshan Group stratotype section zircon U-Pb tectonic significance

Geochronology of the volcanic rocks in the Lu-Zong basin and its significance

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Science China Earth Sciences 2008年第10期51卷 1470-1482页

作者： David COOKE Sebastien MEFFRE Centre of Excellence in Ore Deposits (CODES) University of Tasmania

The Lu-Zong (Lujiang-Zongyang) basin is one of the most important volcanic basins in the middle and lower reaches of the Yangtze River area, China. It comprises four shoshonitic volcanic units, which are, in an ascending order, the Longmenyuan, Zhuanqiao, Shuangmiao and Fushan Groups. The LA-ICP MS U-Pb zircon ages of the four units are: 134.8±1.8 Ma for the Longmenyuan Group, 134.1±1.6 Ma for the Zhuanqiao Group, 130.5±0.8 Ma for the Shuangmiao Group, and 127.1±1.2 Ma for the Fushan Group. The results indicate that all volcanic rocks in the Lu-Zong basin were formed in the Early Cretaceous from about 135 Ma to 127 Ma, lasting 8-10 Ma. There were no Jurassic volcanic activities in all the volcanic basins including the Lu-Zong basin in the middle and lower reaches of the Yangtze River area. This work has provided new chronological results for the further study and understanding of the tec- tonic, magmatic and metallogenic processes of eastern China in the Mesozoic.

关键词： zircon LA-ICP MS dating volcanic rocks geochronologic age Lu-Zong basin

^(40)Ar/^(39)Ar chronology and geochemistry of high-K volcanic rocks in the Mangkang basin, Tibet

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Science China Earth Sciences 2005年第1期48卷 1-12页

作者： ZHANG Huihua, HE Huaiyu, WANG Jianghai & XIE Guanghong Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China College of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China Chinese Academy of Sciences Guangzhou Institute of Geochemistry Guangzhou China Chinese Academy of Sciences Institute of Geology and Geophysics Beijing China College of Life Sciences Sun Yat-Sen University Guangzhou China

Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5 ( 0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5 ( 0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. Et al., implying that they were formed in the same tectonic setting.

关键词： Cenozoic high-K volcanic rocks, 40Ar/39Ar chronology, Mangkang basin, Tibet.

Assessment of seismic ground motion amplification and liquefaction at a volcanic area characterized by residual soils

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Journal of Mountain Science 2020年第3期17卷 740-752页

作者： Luca MATASSONI Andrea FIASCHI Fondazione Parsec Via Galcianese20/H59100 PratoItaly(former)now at CittaMetropolitana di FirenzeDirezione Progetti StrategiciVia Cavour150129 FirenzeItaly Fondazione Parsec Via Galcianese20/H59100 PratoItaly

A seismic hazard was assessed related to site effects at Abbadia San Salvatore, central Italy, on the Mt. Amiata slopes, an ancient volcanic area characterized by residual soils(thick layers of loose to dense sands originated from weathering of the trachydacitic lavas). The seismic ground amplification and soil liquefaction related to these layers were recognized as the major seismic hazards for the area.Geological, geophysical, and geotechnical surveys were carried out on the volcanic rocks. The Horizontal-to-Vertical Spectral Ratio(HVSR) analysis of 252 noise measurements and 29 shear-wave velocity models of the subsoil allowed a seismic microzonation of the studied area, distinguished by thick weathered volcanic sands and shear-wave impedance contrast with respect to the seismic bedrock(volcanic bedrock). The differentiation of classified zones allowed recognition of areas characterized by residual(almost undisturbed) soils from those with soils probably affected by flowing water. The analysis of hazards revealed that peak acceleration by seismic amplification of ground motion exceeded the value set by the national rules(0.175 g) in a restricted area of the zone characterized by the most perturbed soils(Zone D);the potential occurrence of soil liquefaction was also greater in this zone. Finally, the study showed potential high hazards due to site effects of the volcanic mountainous area characterized by residual soils as opposed to an alluvial plain formed by volcanic debris where these effects have generally been more recognized.

关键词： Site effects Residual soils volcanic mountain area Seismic ground amplification Soil liquefaction Shear wave velocity

Basement faults and volcanic rock distributions in the Ordos Basin

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Science China Earth Sciences 2010年第11期53卷 1625-1633页

作者： Li Ming Gao JianRong PetroChina Res Inst Petr Explorat & Dev Beijing 100083 Peoples R China

volcanic rocks in the Ordos Basin are of mainly two types: one in the basin and the other along the margin of the basin. Besides those along the margin, the marginal volcanic rocks also include the volcanic rocks in the Yinshanian orogenic belt north of the basin. Based on the latest collection of gravitational and aeromagnetic data, here we interpret basement faults in the Ordos Basin and its peripheral region, compare the faults derived from aeromagnetic data with those from seismic data, and identify the geological ages of the fault development. Two aeromagnetic anomaly zones exist in the NE-trending faults of the southern basin, and they are in the volcanic basement formed in pre-Paleozoic. These NE-trending faults are the channel of volcanic material upwelling in the early age (Archean-Neoproterozoic), where igneous rocks and sedimentary rocks stack successively on both sides of the continental nucleus. In the Cambrian, the basin interior is relatively stable, but in the Late Paleozoic and Mesozoic, the basin margin underwent a number of volcanic activities, accompanied by the formation of nearly north-south and east-west basement faults in the basin periphery and resulting in accumulation of great amount of volcanic materials. volcanic tuff from the basin periphery is discovered in the central basin and volcanic materials are exposed in the margins of the basin. According to the source-reservoir-cap rock configuration, the basin peripheral igneous traps formed in the Indosinian-Early Yanshanian and Late Hercynian are favorable exploration objectives, and the volcanic rocks in the central basin are the future target of exploration.

关键词： Ordos Basin volcanic rocks basement fault aeromagnetic anomaly hydrocarbon potential

Geochronology and Petrochemistry of volcanic Rocks in the Xaignabouli Area, NW Laos

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Journal of Earth Science 2019年第1期30卷 37-51页

作者： Meifeng Shi Zhenbo Wu Shusheng Liu Zhimin Peng Linnan Guo Fei Nie Siwei Xu Chengdu Center China Geological Survey

An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesitic tuff from the Muang-Nan Formation in the Xaignabouli area, which had been mapped as the Permian–Early Triassic on the 1 : 1 000 000 geological map or Late Carboniferous on the 1 : 200 000 geological maps. Zircon U-Pb dating of three samples yielded weighted mean ages of 235±2.6, 232±1.4 and 278±2.8 Ma, respectively, suggesting a Late Triassic origin for the Nam Hang Formation and an Early Permian origin for the Muang-Nan Formation. Geochemically, they are characterized by depletions in HFSEs(e.g., Nb, Ta, Ti) and high LILE/HFSE ratios, and they have positive zircon ε_(Hf)(t) values of 8.7–15.9, which exhibits the continental arc volcanic affinity and partial melting of subducting oceanic slab in the magma source. Combined with spatial occurrence of the volcanic rock and existing geochronological and geochemical data, we suggest that the Xaignabouli-Luang Prabang volcanic belt can be linked to the Loei-Phetchabun belt. The Permian–Triassic volcanic rocks in this belt might be a product of the Nan back-arc basin eastward subduction.

关键词： volcanic rock zircon U-Pb geochronology geochemistry zircon Lu-Hf isotope Xaignabouli Laos