查看更多>>摘要：In this study,we investigated Early Paleozoic magmatic rocks of the Manlai Formation exposed along the eastern margin of the Lancang terrane to better understand the tectonic history of the Proto-Tethys.We present petrological,geochemical and whole-rock Sr-Nd and zircon Hf isotopic data for basalts and gabbros sampled from the Qianmai mélange.Zircon grains from six basaltic and gabbroic samples yielded U-Pb ages of 495-482 Ma.These rocks are characterized by tholeiitic and Nb-enriched compositions,with Nb/La ratios in the range of 0.38-1.38,similar to the typical Nb-enriched basalts.All the mafic rocks show slightly negative to positive εNd(t)(-1.67 to+4.32)and zircon εHf(t)val-ues(-7.3 to+3.8).Elemental and isotopic data suggest that the Qianmai Nb-enriched mafic rocks were mainly derived from the mixing of an OIB-like source with a subduction-modified mantle wedge source.Together with magmatic and sedimentary records of similar ages in the Lancang terrane and the Baoshan Block,our results reveal Early Paleozoic magmatic and sedimentary sequences along an active margin of the Proto-Tethys.Taking into account the recently identified Early Paleozoic ophiolitic mélange in the Yunxian-Menghai belt,we consider the Qianmai magmatic rocks to represent the prod-ucts of early-stage subduction-related magmatism within a primitive island arc or fore-arc setting asso-ciated with the southward subduction of the Proto-Tethys.We infer that prolonged south-dipping sub-duction on the northern margin of Gondwana persisted from the Cambrian to the Late Ordovician.
查看更多>>摘要：During the Late Paleozoic-Early Mesozoic Era,the sediment transport system and tec-tonic regime in the southeastern margin of the South China Block(SESCB)all changed,significantly affected by the Paleo-Pacific subduction.However,controversy exists about the Paleo-Pacific subduc-tion's initiation time.This study uses detrital zircon U-Pb ages to discuss the Late Triassic source-to-sink system in the SESCB.It provides some references for the Paleo-Pacific subduction process based on crucial age information and zircons'trace elements.The paleogeography and similarity of detrital zircon age distribution indicate that three sinks were found in the SESCB during the Late Triassic:1.the Yangchun-Kaiping-Gaoming area,comprising major age ranges of 260-220,460-400,and 1 200-800 Ma,which might be sourced from the Yunkai terrane;2.the Jiexi-Kanshi-Nanjing area,character-ized by the significant age component of 2 000-1 800 Ma,which corresponded to the Wuyi terrane;3.the Xinan area,consisting of significant age groups of 290-250 and 380-320 Ma,which might be sourced from the magmatic rocks formed by the Huinan Movement and Paleo-Pacific subduction.Note that 290-250 Ma zircons were widely distributed in the Upper Triassic strata,and their trace elements suggested the existence of a magmatic arc near the SESCB during the 290-250 Ma.Thus,we propose that the Paleo-Pacific subduction might have begun in the Early Permian.
查看更多>>摘要：The Luojiashan gabbro is a newly discovered mafic pluton emplaced in the Neoprotero-zoic Yingyangguan Formation in Yingyangguan region of northeastern Guangxi,South China.Com-prehensive whole-rock geochemical and zircon geochronological and Hf isotopic analyses are per-formed on the gabbro and comparisons are made with the coeval mafic-ultramafic sills and dikes locat-ed in Longsheng region of northern Guangxi in order to understand the magmatic origin,evolution,and tectonic setting of the Luojiashan gabbro and to address the location of the suture zone of the Southwestern Jiangnan Orogen(SJO).LA-ICP-MS zircon U-Pb ages obtained from the Luojiashan gabbro show that it was emplaced at~770 Ma.The gabbro contains abundant inherited zircons aged at 0.9-1.3 Ga,consistent with age spectrum of the Cathaysia Block.Chondrite-normalized REE pattern,primitive mantle-normalized trace element spider diagram,incompatible element ratios of Nb/Ta,Zr/Hf,La/Nb,Ba/Th,Th/La,and Ba/La,and Th/Yb-Ta/Yb discrimination diagram of the gabbro are in-dicative of OIB-like geochemical characteristics and of derivation from partially melted garnet perido-tite of the asthenospheric mantle.Tectonic discrimination based on the trace and rare earth elements al-so indicate that the Luojiashan gabbro was emplaced in a within-plate extensional rift setting,probably as a result of Rodinia supercontinent dismantling,lithospheric thinning,and underplating and upwell-ing of the asthenospheric mantle.Based on zircon age,Hf isotopic data and comparison between north-ern and northeastern Guangxi,it is suggested that the Yingyangguan region was tectonically situated in a different tectonic locale from the Longsheng region of northern Guangxi at about 770 Ma during the post-orogenic mafic-ultramafic magmatic event,with the former within the Cathaysia Block and the latter along the southeast margin of Yangtze Block.The suture between the Yangtze and Cathaysia blocks must be located between Yingyangguan of northeastern Guangxi and Longsheng of northern Guangxi.
查看更多>>摘要：Identifying volcanic reservoir types and their distribution patterns in volcanic edifices is important for accurate prediction and exploration of hydrocarbon reservoirs.Herein,we analyzed the distribution patterns of different reservoir levels in volcanic edifices,discussed controlling factors,and reclassified reservoir types.This was done using core observations,whole-rock geochemistry,and reser-voir physical property analysis,combined with logging,drilling,seismic,and oil-gas test data.Reser-voirs can be divided into three classes based on their physical properties.The Mesozoic intermediate and basic rocks formed Class I reservoirs,most lithologies formed Class II reservoirs,and diabase in-trusions and tight volcanic rocks formed Class III reservoirs.Reservoirs form in different lithologies in the Huanghua depression due to weathering.Tectonic faults deepen the influence of weathering leading to the formation of reservoirs in tight.Additionally,volcanic rhythms and fractures control the vertical distribution of Cenozoic basaltic reservoirs.Volcanic reservoirs are classified into five types based on the main controlling factors and distribution patterns in volcanic edifices:tectonic-alteration,vesicle-fracture,weathered-effusive,weathered-eruptive,and weathered-tectonic types.Among these,the weathered-eruptive type can easily form Class I reservoirs,making it the best target for exploration.Whereas the weathered-tectonic and vesicle-fracture types tend to develop Class II reservoirs and can be potential targets.The new classification takes into account the relationship between reservoir levels and their distribution in volcanic edifices,it is more conducive to igneous reservoir prediction in the Huanghua depression.This study provides a novel idea for the classification and comparative study of igneous reservoirs in petroliferous basins.
Ming ShaoTianzhu LeiShuncun ZhangShengyin Zhang...
1482-1498页
查看更多>>摘要：The mudstone,gray tuffite and carbonaceous shale in the Upper Carboniferous Bata-mayineishan Formation(Bashan Formation)are essential source rocks for the volcanic reservoir in eastern Junggar,northwestern China.The kerogen components,vitrinite reflectance,Rock-Eval pyrol-ysis,lipid biomarkers and isotope compositions were measured to understand the provenance and dep-ositional environment of Bashan Formation under the background of volcanic activities.There were 10 and 4 periods of volcanic eruptions identified in the wells CS and DZ,respectively.The source rocks de-veloped in the late or intermittent phase of volcanic activity.The original island arcs of the Early Car-boniferous evolved into the Wucaiwan sag and the Dishuiquan sag in the Bashan Formation.The Wu-caiwan sag inherited the restricted,closed residual sea,which had a slightly anoxic and hypersaline en-vironment.The Dishuiquan sag was generally an oxidizing lacustrine environment,influenced by a ma-rine transgression that may have occurred at the end of the DZIII period during the Late Carbonifer-ous.Although the total organic matter decreased due to the volcanic eruption,ash could cause an in-crease of aquatic organisms,coinciding with increases in salinity and reducibility in the Dishuiquan sag.
查看更多>>摘要：Migration pathways and distances of the oils in reservoir are thought to affect the distri-bution of pyrrolic compounds such as carbazole,its alkyl derivatives(alkylated carbazoles)and benzo-carbazoles,although other factors,including maturity and depositional environments may also affect the distribution of these organic nitrogen compounds.In this study,14 oil samples produced from con-ventional reservoirs in Pauls Valley,south Oklahoma were investigated using organic geochemical tech-niques.The sterane and hopane fingerprints suggest that most of the oils were sourced from the Devo-nian Woodford shale.Maturity parameters consistently indicate that the maturity level of the studied samples are all of similar maturity(Rc=~0.7% ),suggesting the distribution of the organic nitrogen or-ganic compounds is possibly reflecting variations in relative migration distances.The distribution of al-kylcarbazoles revealed a preferential enrichment during migration,with the nitrogen-shielded alkylcar-bazole tending to be enriched relative to the nitrogen-semi-shielded alkylcarbozoles particularly in oils produced close to the Arbuckle uplift to the east.Correspondingly,another family of pyrrolic com-pounds,benzocarbazoles,whose distributions also indicated that the Pauls Valley Woodford oils came from deeper part of the Anadarko Basin as the benzo-[a]/([a]+[c])-carbazole ratios decrease eastwards.In more specific migration systems,although the pyrrolic compound indicators are potentially dis-turbed by the structural complexes,the general migration directions suggest that the studied oils in Pauls Valley Hunton uplift were sourced from the deep basin area,and migrate upwards in porous sedi-ments due to the buoyancy.This study investigates the feasibility of using pyrrolic compounds to esti-mate relative migration distances and will aid in the interpretation of migration history by using the distribution of carbazole,alkylated carbazoles,benzocarbazoles isomers in the Anadarko and Ardmore Basin petroleum systems.
查看更多>>摘要：Most knowledge about the Cretaceous-Paleogene strata in the Tarim Basin is mainly in-ferred from the outcrops at the basin's margin,but first time in the basin.The formation mechanism of the Paleocene basal conglomerate was determined using geochemical isotopes of the breccia from Well PBX1 in the southwestern Tarim Basin.The results showed that the global K/Pg(i.e.,Cretaceous/Paleogene)clay layer boundary was located in the middle of the Paleocene basal conglomerate at the depth of 7 066.75 m in Well PBX1.In the Late Cretaceous,associated with volcanic activities and earth-quakes,the caldera in the Well PBX1 Block formed an annular depression with large elevation differ-ences in response to the Pamir Block collision.As a result,the collapsed breccia with storm tide genesis deposited at the periphery and inside of the depression,characterized by syn-sedimentary deformation.During the Paleocene,multiple sets of interbedded carbonate and collapsed breccia deposited in re-sponse to multi-phased transient transgression-regression cycles.The transportation of breccia exhibit-ed near-source accumulation/extremely close or in-situ rapid accumulation.The studied region is locat-ed in the eastern end of the Tethys Sea,the Late Cretaceous-Early Paleocene breccia is of great signifi-cance for reconstructing the paleogeography of the Tarim basin in Tethys.
查看更多>>摘要：A sedimentological investigation was carried out to reconstruct the paleogeography of the Zagros Foreland Basin.Based on the study of more than 1 000 rock samples,nine carbonate micro-facies and three terrigenous facies were identified.The study reveals that the Maastrichtian succession was deposited in a widespread homoclinal ramp in the High Zagros Basin.Three(Gandom Kar area),two(Ardal area),seven(Gardbishe area),five(Shirmard area),two(Kuh-e-Kamaneh area),three(Kuh-e-Balghar area),and six(Murak area)of depositional sequences(3rd order)were identified.The thickness of the lowstand systems tract(LST)due to activities of local faults and subsidence in the southeast is more than in the central and northwest of the High Zagros Basin during the Early and Ear-ly Middle Maastrichtian.During the Middle Maastrichtian,the shallow and deep marine deposits were formed during the transgressive systems tract(TST)and highstand systems tract(HST)in this basin and the rate of subsidence in the center of this basin(Gardbishe area)is higher than in other areas and the platform was drowned in this area.The falling relative sea-level due to activities of local faults led to that marine deposits were absent in all parts of the High Zagros Basin(except the south part)during the Late Maastrichtian.Paleogeographical studies on the Zagros Basin during the Late Campanian-Maastrichtian showed the following results:shallow marine environments were developed in the south-east of this basin,and the turbidite,delta,and fluvial environments in the northwest were developed more than in other areas.
查看更多>>摘要：Landslides pose a frequent geological threat,endangering both productivity and the well-being of human life and property.In recent years,landslides have received widespread attention in var-ious fields.This article presents a comprehensive review of landslide research in the Qinling Moun-tains,China.The first part introduces landslide investigation and inventory,which include manual vi-sual interpretation and automatic landslide extraction.The second part discusses the types,characteris-tics,and temporal-spatial distribution of landslides in the Qinling Mountains.In the third part,the mechanisms and stability analysis of landslides are explored,along with a discussion of the applicabili-ty of various simulation methods.The fourth part focuses on significant studies related to landslide evaluation,including susceptibility,hazard,and risk assessment.The fifth part addresses landslide monitoring and early warning systems.Finally,an assessment is made of the current issues and re-search status concerning landslide studies in the Qinling Mountains,followed by a discussion on future research directions.
查看更多>>摘要：This paper introduces the use of point cloud processing for extracting 3D rock structure and the 3DEC-related reconstruction of slope failure,based on a case study of the 2019 Pinglu rockfall.The basic processing procedure involves:(1)computing the point normal for HSV-rendering of point cloud;(2)automatically clustering the discontinuity sets;(3)extracting the set-based point clouds;(4)estimating of set-based mean orientation,spacing,and persistence;(5)identifying the block-forming ar-rays of discontinuity sets for the assessment of stability.The effectiveness of our rock structure process-ing has been proved by 3D distinct element back analysis.The results show that SfM modelling and rock structure computing provides enormous cost,time and safety incentives in standard engineering practice.
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