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Origin and tectonic setting of low-Si alkaline magma

Science China Earth Sciences 2024年第5期67卷 1417-1435页

作者： Qiushi ZHOU Rui WANG State Key Laboratory of Geological Processes and Mineral Resources and Institute of Earth SciencesChina University of GeosciencesBeijing 100083China Frontiers Science Center for Deep-time Digital Earth China University of Geosciences(Beijing)Beijing 100083China

Despite of the relatively rare occurrence of alkaline igneous rocks on Earth, they are the most diverse group of igneous rocks due to variations in their mineral assemblages and geochemical compositions. Alkaline igneous rocks are generally characterized by Si undersaturation, and K-Na(and in some cases C) enrichment. Although there is no unified alkaline igneous rock classification scheme, diagrams such as total alkalis-SiO_(2) or K_(2)O-SiO_(2) can be used to classify alkaline igneous rocks. The origins of silica-saturated alkaline rocks(SiO_(2)>52 wt.%) are relatively complex because multiple episodes of magmatism are often involved, therefore most studies have focused on the origins of silica-undersaturated alkaline magmas.Numerous experimental petrological studies have been conducted in the past few decades. Initially, it was considered that enrichment of trace elements was only achieved by low-degree partial melting of mantle peridotite, but the experimental melts could not reproduce the geochemical composition of natural alkaline igneous rocks. Subsequent studies have focused on carbonate-bearing eclogites that represent the average component of subducted oceanic crust. Although experimental studies indicate that silica-undersaturated and alkali-oversaturated melts can be generated from eclogites, some studies have considered that natural silica-undersaturated alkaline igneous rocks are the result of multi-stage source enrichment by incompatible elements. Low-degree partial melts of the mantle can be emplaced in the lithospheric mantle, forming veins consisting of phlogopite, amphibole, and pyroxene. Melting experiments including these components show that the produced melts better reproduce the naturally occurring silica-undersaturated alkaline magmas. Silica-deficient alkaline igneous rocks occur in various tectonic settings. Those in intraplate and divergent settings(i.e., mainly continental rifts) normally involve contributions from recycled components such as subducted slabs at the mantle transition z

关键词： Alkaline igneous rock tectonic setting Petrogenesis Big data

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Geochemical characteristics of Neogene sandstones of the East and West Siang Districts of Arunachal Pradesh,NE India:implications for source-area weathering,provenance,and tectonic setting

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Acta Geochimica 2022年第1期41卷 100-120页

作者： Roshmi Boruah Jayanta Jivan Laskar Department of Geological Sciences Gauhati UniversityGuwahatiAssam 781014India

Sandstones from the Neogene Siwalik successions of the East and West Siang Districts of Arunachal Pradesh were analyzed to evaluate source-area weathering,provenance,and tectonic setting by using major,trace,and rare earth elements(REEs)as proxies.The sandstones are classified as lithic arenite and wacke arenite based on their mineralogical compositions.The values of different weathering indices such as Chemical Index of Alteration(CIA;60.93–89.86)and Chemical Index of Weathering(CIW;40–96.8)suggest moderate to intense weathering in the source area.The plot of Th/Sc versus Zr/Sc indicates enrichment of zircon by sediment sorting and/or recycling from a weathered source.The high positive correlation between Al2 O_(3) and K2 O points towards a strong influence of the constituent clay minerals on the major oxide composition of the sandstones.Petrographic analysis together with enriched LREE,flat HREE,negative Eu anomalies(Eu/Eu^(*)=0.47 to 0.90)in the chondrite-normalized diagrams,and the ratios of La/Sc,La/Co,Th/Sc,Th/Co,Cr/Th collectively suggests that the Neogene sediments were derived from felsic igneous and/or reworked sedimentary/metasedimentary sources in an upper continental crustal setting.The geochemical characteristics of the studied Neogene Siwalik sandstones indicate that the sediments were sourced from pre-Himalayan gneisses and granitoids together with metabasic rocks,which had formed in a passive margin tectonic setup.

关键词： Geochemistry Neogene sandstones Arunachal Pradesh Paleo-weathering Provenance tectonic setting

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Effects of tectonic setting and Hydraulic Properties on Silent Large-Scale Landslides:A Case Study of the Zhaobishan Landslide,China

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International Journal of Disaster Risk Science 2023年第4期14卷 600-617页

作者： Shufeng Tian Guisheng Hu Ningsheng Chen Mahfuzur Rahman Huayong Ni Marcelo Somos-Valenzuela Key Lab of Mountain Hazards and Surface Processes Institute of Mountain Hazards and Environment Chinese Academy of Sciences University of Chinese Academy of Sciences Academy of Plateau Science and Sustainability Kathmandu Center for Research and Education Chinese Academy of Sciences-Tribhuvan University Department of Civil Engineering International University of Business Agriculture and Technology(IUBAT) Department of Civil Engineering Kunsan National University Institute of Exploration Technology China Geological Survey Department of Forest Sciences Faculty of Agriculture and Environmental SciencesUniversidad de La Frontera

Unlike strong earthquake-triggered or heavy rainfall-triggered landslides,silent large-scale landslides(SLL) occur without significant triggering factors and cause unexpected significant disaster risks and mass casualties.Understanding the initiation mechanism of SLLs is crucial for risk reduction.In this study,the mechanism of the Zhaobishan SLL was investigated,and the SLL was jointly controlled by weak-soil(fractured rock mass) and strong-water(abundant water replenishment)conditions under the impact of active tectonism and complex hydraulic properties.Strong tectonic uplift,high fault density,and historical earthquakes led to weak-soil conditions conducive to the Zhaobishan SLL.The combined effect of unique lithology,antiform,and cultivated land contributed to the water replenishment characteristics of extensive runoff confluence(3.16 times that of the landslide body) and supported long-distance groundwater replenishment,thereby forming strongwater conditions for the landslide.The amplified seepage amount caused the strength of the soil mass on the sliding surface to decrease to 0.4 times its initial strength,eventually triggering the Zhaobishan SLL,which occurred 4.6 days after the peak rainfall.Moreover,the landslide deposits have accumulated on the semi-diagenetic clay rock,thereby controlling the subsequent recurring debris flows in the Lengzi Gully.To reduce disaster risk of SLL in vulnerable mountainous regions,the water confluence area behind the main scarp of the landslides and the hysteresis characteristics between landslides and peak rainfall should be further considered,and recurring debris flows following massive landslides also should be focused.

关键词： Debris flow Hydraulic properties Risk reduction Runoff amplification Silent large-scale landslides (SLL) tectonic setting

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Petrogenesis and tectonic implications of the Silurian adakitic granitoids in the eastern segment of the Qilian Orogenic Belt,Northwest China

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Acta Geochimica 2024年第1期43卷 72-86页

作者： Jiao-Long Zhao Xiao-Jun Huang Pei-Qing Hu Zhen-Xi Yang Ying Fan Er-Teng Wang Fu-Bo Yang Jing-Yu Zhang School of Earth Sciences Key Laboratory of Mineral Resources in Western China(Gansu Province)Lanzhou UniversityLanzhou 730000China Nuclear Industry 247 Brigade Tianjin North China Geological Survey BureauTianjin 301800China Fourth Institute of Geological and Mineral Exploration of Gansu Provincial Bureau of Geology and Mineral Resources Jiuquan 735000China

Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.

关键词： Silurian adakitic granitoids Petrogenesis tectonic setting Qilian Orogenic Belt

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Efects of tectonic setting and Hydraulic Properties on Silent Large‑Scale Landslides: A Case Study of the Zhaobishan Landslide,China

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International Journal of Disaster Risk Science 2023年第4期14卷 600-617页

作者： Shufeng Tian Guisheng Hu Ningsheng Chen Mahfuzur Rahman Huayong Ni Marcelo Somos‑Valenzuela Key Lab of Mountain Hazards and Surface Processes Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610299China University of Chinese Academy of Sciences Beijing 100049China Academy of Plateau Science and Sustainability Xining 810016China Kathmandu Center for Research and Education Chinese Academy of Sciences-Tribhuvan UniversityBeijing 100101China Department of Civil Engineering International University of Business Agriculture and Technology(IUBAT)Dhaka 1230Bangladesh Department of Civil Engineering Kunsan National UniversityGunsan 54150Republic of Korea Institute of Exploration Technology China Geological SurveyChengdu 611734China Department of Forest Sciences Faculty of Agriculture and Environmental SciencesUniversidad de La Frontera4780000 TemucoChile

Unlike strong earthquake-triggered or heavy rainfall-triggered landslides,silent large-scale landslides(SLL)occur without signifcant triggering factors and cause unexpected signifcant disaster risks and mass casualties.Understanding the initiation mechanism of SLLs is crucial for risk reduction.In this study,the mechanism of the Zhaobishan SLL was investigated,and the SLL was jointly controlled by weak-soil(fractured rock mass)and strong-water(abundant water replenishment)conditions under the impact of active tectonism and complex hydraulic properties.Strong tectonic uplift,high fault density,and historical earthquakes led to weak-soil conditions conducive to the Zhaobishan SLL.The combined efect of unique lithology,antiform,and cultivated land contributed to the water replenishment characteristics of extensive runof confuence(3.16 times that of the landslide body)and supported long-distance groundwater replenishment,thereby forming strongwater conditions for the landslide.The amplifed seepage amount caused the strength of the soil mass on the sliding surface to decrease to 0.4 times its initial strength,eventually triggering the Zhaobishan SLL,which occurred 4.6 days after the peak rainfall.Moreover,the landslide deposits have accumulated on the semi-diagenetic clay rock,thereby controlling the subsequent recurring debris fows in the Lengzi Gully.To reduce disaster risk of SLL in vulnerable mountainous regions,the water confuence area behind the main scarp of the landslides and the hysteresis characteristics between landslides and peak rainfall should be further considered,and recurring debris fows following massive landslides also should be focused.

关键词： Debris fow Hydraulic properties Risk reduction Runof amplifcation Silent large-scale landslides(SLL) tectonic setting

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Magma source and tectonic setting of the Dunde granite in the Western Tianshan:constraints from geochronology,geochemistry,and Sr–Nd–Hf isotopes

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地球化学学报(英文) 2023年第5期42卷 879-894页

作者： Zhaode Xia Haibo Ding Yanjiao Ru School of Earth Science and Resources Chang’an UniversityXi’an 710054ShaanxiChina The Third Geological Branch Xinjiang Geological and Mineral BureauKuerleXinjiang 841000China Geophysical and Geochemical Exploration Corporation Bureau of Geological Exploration for Nonferrous Metals in Northwest ChinaXi’an 710068ShaanxiChina

The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Dunde mining area in order to constrain the tectonicmagmatic activities and metallogenesis of this region.Granites in the southwest of Dunde mining area are mainly syenogranites intruded into volcanics of the Dahalajunshan Formation in the Early Carboniferous,and they are far from the area where ore bodies and mineralized altered rocks are widely developed.LA-ICP-MS U–Pb zircon dating indicates that Dunde syenogranite was at 306.8±1.0 Ma,which could constrain the upper limit of metallogenic age for this deposit.The Dunde granites are high SiO_(2)(73.41–80.07 wt%),high differentiation index(D.I.=89.7–95.0),weakly peraluminous to metaluminous(A/CNK=0.94–1.08),and they are enriched in LILE and LREE and depleted in Eu,Ba,Sr and P_(2)O_(5),indicating that they belong to highly fractionated Ⅰ-type granite.Based on εHf values(+9.2 to+10.5)for zircon and high εNd(-t)values(+4.7 to+5.8)for whole-rock,and the two-stage model ages for 601–735 Ma,suggest that the magma source could be the juvenile lower crust.Combined with regional geological setting,the 306.8 Ma Dunde granites are formed in post-collision extensional tectonic setting.

关键词： Granite Geochemistry Magma source tectonic setting Dunde deposit Western Tianshan

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Provenance, tectonic setting and Geochemistry of Ahwaz Sandstone Member(Asmari Formation, Oligo-Miocene), Marun Oilfield, Zagros Basin, SW Iran

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Acta Geologica Sinica(English Edition) 2014年第3期88卷 931-948页

作者： Shahram AVARJANI Asadollah MAHBOUBI Reza MOUSSAVI-HARAMI Hassan AMIRI-BAKHTIAR Department of Geology Faculty of Science Ferdowsi University of MashhadIran Department of Geology National Iranian south Oil CompanyIran

The Asmari Formation deposited in the Zagros foreland basin during the OligoceneMiocene.Lithologically,the Asmari Formation consists of limestone,dolomitic limestone,dolomite,argillaceous limestone,some anhydrite （Kalhur Member） and sandstones （Ahwaz Member）.This study is based on the analysis of core samples from four subsurface sections （wells Mn-68,Mn-281,Mn-292 and Mn-312） in the Marun Oilfieid in the Dezful embayment subzone in order to infer their provenance and tectonic setting of the Ahwaz Sandstone Member.Petrographical data reveal that the Ahwaz Sandstone comprises 97.5% quartz,1.6% feldspar,and 0.9% rock fragments and all samples are classified as quartz arenites.The provenance and tectonic setting of the Ahwaz Sandstone have been assessed using integrated petrographic and geochemical studies.Petrographic analysis reveals that mono-and poly-crystalline quartz grains from metamorphic and igneous rocks of a craton interior setting were the dominant sources.Chemically,major and trace element concentrations in the rocks of the Ahwaz Sandstone indicate deposition in a passive continental margin setting.As indicated by the CIW index （chemical index of weathering） of the Ahwaz Sandstone （average value of 82） their source area underwent ＂intense＂ recycling but ＂moderate to high＂ degree of chemical weathering.The petrography and geochemistry results are consistent with a tropical,humid climate and low-relief highlands.

关键词： Asmari Formation Dezful Embayment provenance tectonic setting sandstone,geochemistry Ahwaz Sandstone Member

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Geochemistry of the upper Permian sandstones in the Dalong Formation in the South Yellow Sea Basin,East China:implications to provenance,weathering,and tectonic setting

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Journal of Oceanology and Limnology 2021年第3期39卷 814-829页

作者： Yuxiao HUANG Xingwei GUO Xunhua ZHANG Laixing CAI Ocean University of China Qingdao 266071China Qingdao Institute of Marine Geology Qingdao 266071China Laboratory for Marine Mineral Resources Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China Institute of Oceanology Chinese Academy of SciencesQingdao 266071China

To reconstruct the paleoenvironment,the petrography and geochemical compositions of the upper Permian Dalong Formation(Fm)(P_(3)d)sandstones in the Central Uplift,South Yellow Sea Basin,was investigated,after which the provenance,tectonic setting,weathering conditions,and diagenetic history were determined.The Dalong Fm is mainly composed of sandstones with a few mudstones and limestones.The petrographic analysis showed that the P_(3)d sandstones are in low maturity and could be classified into feldspar sandstone and lithic sandstone on average framework composition of Q_(63)F_(16)L_(21).The major and trace element results show that Dalong Fm sandstones are enriched in Rb and depleted in Cr and Ni compared with the upper continental crust(UCC).The chemical weathering intensity is weak to low moderate in the source area as indicated by the chemical index of alteration(CIA)and other results from a variety of methods.The diagenetic process included three main stages:eodiagenesis,mesodiagenesis,and telodiagenesis.tectonic discrimination plots show that the source areas were an active continental margin(ACM)and a passive continental margin(PCM),which may have been related to the northward movement of the Lower Yangtze Plate(LYP)and the collision between the LYP and the North China Plate(NCP).

关键词： rock geochemistry rock weathering tectonic setting evolution of rock South Yellow Sea Basin

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Detrital Mode and Geochemistry of the Shurijeh Formation (Late Jurassic-Early Cretaceous) in the Central and Western Parts of the Intracontinental Kopet-Dagh Basin, NE Iran: Implications for Provenance, tectonic setting and Weathering Processes

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Acta Geologica Sinica(English Edition) 2013年第4期87卷 1058-1080页

作者： M. MORTAZAVI R. MOUSSAVI-HARAMI A. MAHBOUBI Department of Geology Faculty of science Ferdowsi University of Mashhad

Petrographical and geochemical methods were combined to investigate the provenance, geodynamic and weathering history of the Shurijeh sandstones, Kopet-Dagh Basin. The point-counting method and XRF technique are used for modal and geochemical analyses. Based on petrographical examinations, it seems that the Shurijeh sandstones are mainly deposited in the craton interior and recycled orogen belts. In addition to petrographical investigation, geochemical analyses （major oxides and trace elements） of Late Jurassic-Early Cretaceous rocks reveal that the sedimentation processes are performed in a passive continental margin. Such interpretation is supported with geodynamic and paleogeographical studies of the Kopeh-Dagh basin during this time. The geochemical investigations suggested that the composition of probable source rocks mostly was acidic-intermediate with minor mafic igneous rocks. Based on the above, Paleo-Tethys remnants and their collision-related granitoids, in the south and west of Mashhad, may have been the source area for these rocks. CIA values, which range from 63.8 to 94.9 in samples, are suggesting a moderate to relatively high degree of alteration （weathering） in the source area. Therefore, petrographical and paleogeographical studies of siliciclastic rocks can be used for the provenance, tectonic setting and paleoweathering studies in the source area.

关键词： petrography geochemistry tectonic setting provenance weathering processes ShurijehFormation

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Geochemical Characteristics of Early Permian Pyroclastic Rocks in the Jimunai Basin,West Junggar,Xinjiang(NW China):Implications for Provenance and tectonic setting

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Acta Geologica Sinica(English Edition) 2021年第3期95卷 794-809页

作者： SHANGGUAN Yunfei ZHUANG Xinguo LI Baoqing LI Jing QUEROL Xavier LIU Shunbin Key Laboratory of tectonics and Petroleum Resources of Ministry of Education China University of GeosciencesWuhan 430074China Institute of Environmental Assessment and Water Research IDÆA-CSIC C/Jordi Girona18–26Barcelona 08034Spain Xinjiang Bureau of Prospecting and Development of Geology and Mineral Resources Urumqi 830000China

During the Late Paleozoic,West Junggar(Xinjiang,NW China)experienced a shift in tectonic setting from compression to extension.Ha'erjiao is an important area for investigating collisional structures,post–collisional structures,and magmatic activities.Based on the petrological and geochemical characteristics of pyroclastic and other volcanic rocks in the Permian Kalagang Formation from the borehole ZKH1205 in the Jimunai Basin,the main types of source rock for the pyroclastic rocks deposited in the basin are identified and their implications for the Early Permian tectonic setting examined.The abundance of basalt and andesite lithic fragments in the pyroclastic rocks,together with the REE characteristics and the contents of transition and high field strength elements show that the source rocks were chiefly intermediate–basic volcanic rocks.High ICV values,low CIA values,low Rb/Sr ratios,low Th/U ratios and the mineralogical features suggest weak chemical weathering of the source rocks;the geochemical patterns of the pyroclastic rocks might not only have been impacted by crustal contamination but also might be related to the nature of the magma from the source area.The geochemical properties of the pyroclastic rocks distinguish them from arc-related ones,and such samples plot in the within-plate basalt(WPB)field in some diagrams.This is consistent with the formation background of the Early Permian volcanic rocks in this region.

关键词： pyroclastic rock provenance tectonic setting Kungurian Central Asian Orogenic Belt

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