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Geochemistry, zircon U–Pb geochronology, and Hf isotopes of S-type granite in the Baoshan block, constraints on the age and evolution of the Proto-Tethys
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作者 Jianjun Zhang Chuanlong Mou +3 位作者 Chendong Liu Yong Zhang Ting Chen Hualiang Li 《Acta Geochimica》 EI CAS CSCD 2024年第1期40-58,共19页
Geochemistry, zircon U–Pb geochronology, and Hf isotope data for the Early Paleozoic granites in the Baoshan Block reveal the Early Paleozoic tectonic evolution of the Proto-Tethys. The samples are high-K, calcalkali... Geochemistry, zircon U–Pb geochronology, and Hf isotope data for the Early Paleozoic granites in the Baoshan Block reveal the Early Paleozoic tectonic evolution of the Proto-Tethys. The samples are high-K, calcalkaline, strongly peraluminous rocks with A/CNK values of 1.37–1.46, are enriched in SiO2, K2O, and Rb, and are depleted in Nb, P, Ti, Eu, and heavy rare earth elements,which indicates the crystallization fractionation of the granitic magma. Zircon U–Pb dating indicates that they formed in ca. 480 Ma. The Nansa granites have εHf(t) values ranging from-16.04 to 4.36 with corresponding TC DMages of 2.10–0.81 Ga, which suggests the magmas derived from the partial melting of ancient metasedimentary with minor involvement of mantle-derived components. A synthesis of data for the Early Paleozoic igneous rocks in the Baoshan block and adjacent(Tengchong,Qiangtang, Sibumasu, Himalaya, etc.) blocks indicates that these blocks were all aligned along the proto-Tethyan margin of East Gondwana in the Early Paleozoic. The Early Paleozoic S-type granites from Nansa were generated in a high-temperature and low-pressure(HTLP) extensional tectonic setting, which resulted from Andean-type orogeny instead of the final assembly of Gondwana or crustal extension in a non-arc environment. In certain places, an expanding environment may exist in opposition to the tectonic backdrop of the lithosphere’s thickening and shortening, leading the crust to melt and decompress,mantle-derived materials to mix, and a small quantity of peraluminous granite to emerge. 展开更多
关键词 Baoshan block Early Paleozoic granite GEOCHEMISTRY ZIRCON GEOCHRONOLOGY Hf isotope
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Mechanical properties and energy evolution of Beishan shallow-layer granite under different unloading paths
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作者 WANG Chuanle LI Erbing +4 位作者 ZHANG Dengke HAN Yang LU Hui HE Kang DU Guangyin 《Journal of Mountain Science》 SCIE CSCD 2024年第5期1728-1744,共17页
Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characte... Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characteristics, and strain energy evolution of the Beishan shallow-layer granite used in triaxial unloading tests were investigated in this study. Three groups of triaxial tests, namely, conventional triaxial compression test(Group Ⅰ), maintaining deviatoric stress synchronously unloading confining pressure test(Group Ⅱ), and loading axial pressure synchronously unloading confining pressure test(Group Ⅲ), were carried out for the cylindrical granite specimens. AE monitoring device was utilized in these tests to determine the degree to which the AE waves and AE events reflected the degree of rock damage. In addition, the crack stress thresholds of the specimens were determined by volumetric strain method and AE parameter method, and strain energy evolution of the rock was explored in different damage stages. The results show that the shallow-layer granite experiences brittle failure during the triaxial loading test and unloading test, and the rock has a greater damage degree during the unloading test. The crack stress thresholds of these samples vary greatly between tests, but the threshold ratios of all samples are similar in the same crack damage stage. The Mogi-Coulomb strength criterion can better describe the unloading failure strength of the rock. The evolution of the AE parameter characteristics and strain energy differs between the specimens used in different stress path tests. The dissipative strain energy is the largest in Group Ⅱ and the smallest in Group Ⅰ. 展开更多
关键词 Beishan granite Unloading test Mechanical properties Damage mechanism Acoustic emission Strain energy
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Field testing of shear strength of granite residual soils
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作者 Song Yin Pengfei Liu +3 位作者 Xianwei Zhang Wenyuan He Pan Yan Yuzhou Sun 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第9期3718-3732,共15页
The characteristics of residual soils are very different from those of sedimentary soils.Although the strength characteristics of sedimentary soils have been studied extensively,the shear strength characteristics of g... The characteristics of residual soils are very different from those of sedimentary soils.Although the strength characteristics of sedimentary soils have been studied extensively,the shear strength characteristics of granitic residual soils(GRS)subjected to the weathering of parent rocks have rarely been investigated.In this study,the shear strength characteristics of GRS in the Taishan area of southeast China(TSGRS)were studied by field and laboratory tests.The field tests consisted of a cone penetration test(CPT),borehole shear test(BST),self-boring pressuremeter test(SBPT),and seismic dilatometer Marchetti test(SDMT).The shortcomings of laboratory testing are obvious,with potential disturbances arising through the sampling,transportation,and preparation of soil samples.Due to the special structure of GRS samples and the ease of disturbance,the results obtained from laboratory tests were generally lower than those obtained from situ tests.The CPT and scanning electron microscopy(SEM)results indicated significant weathering and crustal hardening in the shallow TSGRS.This resulted in significant differences in the strength and strength parameters of shallow soil obtained by the BST.Based on the SDMT and SBPT results,a comprehensive evaluation method of shear strength for TSGRS was proposed.The SBPT was suitable for evaluating the strength of shallow GRS.The material index(ID)and horizontal stress index(KD)values obtained by the SDMT satisfied the empirical relationship proposed by Marchetti based on the ID index,and were therefore considered suitable for the evaluation of the shear strength of deep GRS. 展开更多
关键词 granite residual soils Shear strength Field tests Self-boring pressuremeter Seismic dilatometer Borehole shear test
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Zircon U-Pb Chronology and Whole-rock Sr-Nd Isotope Compositions of Granite Porphyry in the Kaladaban Area of the Northern Altyn
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作者 JIA Wenbin LI Yongsheng +1 位作者 MI Kuifeng YU Xiaofei 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2020年第1期200-201,共2页
Objective The Altyn Tagh marks the northern margin of the Qinghai-Tibet Plateau and lies between the Tarim block to the north and the Qaidam block,Qilian Orogen,and Kunlun orogenic belt to the south.The Altyn Tagh reg... Objective The Altyn Tagh marks the northern margin of the Qinghai-Tibet Plateau and lies between the Tarim block to the north and the Qaidam block,Qilian Orogen,and Kunlun orogenic belt to the south.The Altyn Tagh region contains ophiolite,high-to ultrahigh-pressure metamorphic rocks,and igneous rocks.Previous research has virified the occurrence of continental rifting,subduction,slab roll-back,and collision between the Tarim block and Proto-Tethys oceanic plate.Moreover,Kaladaban volcanic rocks are mainly distributed in the north Altyn region.Studies of the magmatic evolution of this region have proposed that Altyn oceanic plate was subducted during the Ordovician(Han et al.,2012;Wang et al.,2017).However,the specific timing and other aspects of the subduction are debated,and an investigation of granite porphyry in the Kaladaban area would improve our understanding of this subduction event.In this study,we present new U-Pb zircon dating result and Sr-Nd isotope composition data for granite porphyry from the North Altyn region.The objective is to constrain the timing of subduction of the North Altyn oceanic plate and establish the petrogenesis and magma source of the granite porphyry. 展开更多
关键词 ZIRCON U-PB CHRONOLOGY and Whole-rock SR-ND Isotope Compositions of granite PORPHYRY in the Kaladaban Area of the NORTHERN Altyn NORTHERN
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A coupled thermo-mechanical peridynamic model for fracture behavior of granite subjected to heating and water-cooling processes 被引量:1
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作者 Luming Zhou Zhende Zhu 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第6期2006-2018,共13页
Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The... Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The laboratory uniaxial compression experiments were also conducted.Then,a coupled thermo-mechanical ordinary state-based peridynamic(OSB-PD)model and corresponding numerical scheme were developed to simulate the damage of rocks after the heating and cooling processes,and the change of crack evolution process was predicted.The results demonstrate that elevated heating temperatures exacerbate the thermal damage to the specimens,resulting in a decrease in peak strength and an increase in ductility of granite.The escalating occurrence of thermal-induced cracks significantly affects the crack evolution process during the loading phase.The numerical results accurately reproduce the damage and fracture characteristics of the granite under different final heating temperatures(FHTs),which are consistent with the test results in terms of strength,crack evolution process,and failure mode. 展开更多
关键词 Peridynamics(PD) granite Heating and cooling Damage and fracture Uniaxial compression
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Numerical simulation of microwave-induced cracking and melting of granite based on mineral microscopic models
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作者 Xiaoli Su Diyuan Li +3 位作者 Junjie Zhao Mimi Wang Xing Su Aohui Zhou 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第7期1512-1524,共13页
This study introduces a coupled electromagnetic–thermal–mechanical model to reveal the mechanisms of microcracking and mineral melting of polymineralic rocks under microwave radiation.Experimental tests validate the... This study introduces a coupled electromagnetic–thermal–mechanical model to reveal the mechanisms of microcracking and mineral melting of polymineralic rocks under microwave radiation.Experimental tests validate the rationality of the proposed model.Embedding microscopic mineral sections into the granite model for simulation shows that uneven temperature gradients create distinct molten,porous,and nonmolten zones on the fracture surface.Moreover,the varying thermal expansion coefficients and Young's moduli among the minerals induce significant thermal stress at the mineral boundaries.Quartz and biotite with higher thermal expansion coefficients are subjected to compression,whereas plagioclase with smaller coefficients experiences tensile stress.In the molten zone,quartz undergoes transgranular cracking due to theα–βphase transition.The local high temperatures also induce melting phase transitions in biotite and feldspar.This numerical study provides new insights into the distribution of thermal stress and mineral phase changes in rocks under microwave irradiation. 展开更多
关键词 MICROWAVE numerical modeling microcracking phase change granite
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Geochronology and Geochemistry of the Xingxingxia Triassic A-type Granites in Central Tianshan,NW China:Petrogenesis and Tectonic Implications
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作者 HUANG Zengbao LI Xiyao +1 位作者 ZHAO Hao LU Qing 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2024年第2期337-351,共15页
The Triassic granitoids in Central Tianshan play a key role in determining the petrogenesis and tectonic evolution on the southern margin of the Central Asian orogenic belt.In this study,we present SHRIMP zircon U-Pb ... The Triassic granitoids in Central Tianshan play a key role in determining the petrogenesis and tectonic evolution on the southern margin of the Central Asian orogenic belt.In this study,we present SHRIMP zircon U-Pb ages,Hf isotopic and geochemical data on the Xingxingxia biotite granite,amazonite granite and granitic pegmatite in Central Tianshan,NW China.Zircon U-Pb dating yielded formation ages of 242 Ma for the biotite granite and 240 Ma for the amazonite granite.These granitoid rocks have high K_(2)O with low MgO and CaO contents.They are enriched in Nb,Ta,Hf and Y,while being depleted in Ba and Sr,showing flat HREE patterns and negative Eu anomalies.They have typical A-type granite geochemical signatures with high Ga/A_(1)(8–13)and TFeO/(TFeO+MgO)ratios,showing an A_(2) affinity for biotite granite and an A_(1) affinity for amazonite granite and granitic pegmatite.Zircon ε_(Hf)(t)values of the granitoids are 0.45–2.66,with Hf model ages of 0.99–1.17 Ga.This suggests that these A-type granites originated from partial melting of the lower crust.We propose that Xingxingxia Triassic A-type granites formed under lithospheric extension from post-orogenic to anorogenic intraplate settings and NE-trending regional strike-slip fault-controlled magma emplacement in the upper crust. 展开更多
关键词 TRIASSIC A-type granite Xingxingxia Central Tianshan Central Asian orogenic belt
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Petrogenesis and Tectonic Significance of Shenxianshui Alkaline Granite in Gejiu,Yunnan Province,China
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作者 YANG Rong CHEN Yongqing 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2024年第2期368-385,共18页
The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous.Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67±0.7 to 85.97±0... The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous.Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67±0.7 to 85.97±0.6 Ma.The intrusive rocks are peraluminous(A/CNK=1.03 to 1.33)and calc-alkaline,showing an affinity towards I-type granite.Large ion lithophilic elements are enriched in K and Rb,while high field strength elements are depleted.Moreover,light rare earth elements are significantly enriched,showing a slight negative Eu anomaly(Eu/Eu^(*)=0.39 to 0.58).Shenxianshui granite has a relatively high initial Sr isotope ratio(^(87)Sr/^(86)Sr)_(i)(0.7098-0.7105),negative ε_(Nd)(t)values(−7.99 to−7.44)and negative ε_(Hf)(t)values(−8.37 to−2.58).Combined with previous studies,these characteristics suggest that the Shenxianshui alkaline granites were formed in a post-collision extensional environment.The alkaline granitic magma possibly originated from the partial melting of the lower crust during the Mesoproterozoic era and may have contained mantle source materials.Shenxianshui alkaline granite was formed from mixed magma with a high degree of crystal differentiation.The abundance of ore-forming elements indicates that Shenxianshui granite has the potential to mineralize key metals and rare earth elements. 展开更多
关键词 I-type granite zircon U-Pb geochronology Sr-Nd-Pb isotopes Hf isotope Gejiu
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Prediction and critical transition mechanism for granite fracture:Insights from critical slowing down theory
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作者 WANG Chun-lai ZHOU Bao-kun +6 位作者 LI Chang-feng WEN Zhi-jie BAI Zhi-an ZHU Chao-yang SUN Liang XUE Xu-hui CAO Peng 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第8期2748-2764,共17页
Rock fracture warning is one of the significant challenges in rock mechanics.Many true triaxial and synchronous acoustic emission(AE)tests were conducted on granite samples.The investigation focused on the characteris... Rock fracture warning is one of the significant challenges in rock mechanics.Many true triaxial and synchronous acoustic emission(AE)tests were conducted on granite samples.The investigation focused on the characteristics of AE signals preceding granite fracture,based on the critical slowing down(CSD)theory.The granite undergoes a transition from the stable phase to the fracture phase and exhibits a clear CSD phenomenon,characterized by a pronounced increase in variance and autocorrelation coefficient.The variance mutation points were found to be more identifiable and suitable as the primary criterion for predicting precursor information related to granite fracture,compared to the autocorrelation coefficient.It is noteworthy to emphasize that the CSD factor holds greater potential in elucidating the underlying mechanisms responsible for the critical transition of granite fracture,in comparison to the AE timing parameters.Furthermore,a novel multi-parameter collaborative prediction method for rock fracture was developed by comprehensively analyzing predictive information,including abnormal variation modes and the CSD factor of AE characteristic parameters.This method enhances the understanding and prediction of rock fracture-related geohazards. 展开更多
关键词 granite triaxial compression acoustic emission rock fracture critical slowing down theory
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U-Pb zircon ages and petrogeochemistry and tectonic implications of gabbro and granite in southwest Lahad Datu area of Sabah, Malaysia
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作者 Zhigang Zhao Wu Tang +3 位作者 Shixiang Liu Huafeng Tang Pujun Wang Zhiwen Tian 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2024年第2期94-110,共17页
The southwest Lahad Datu felsic rocks were previously thought to have formed in the late Triassic as part of the microcontinental crystalline basement.Based on U-Pb ages,geochemistry,and the Hfisotopes of zircon from ... The southwest Lahad Datu felsic rocks were previously thought to have formed in the late Triassic as part of the microcontinental crystalline basement.Based on U-Pb ages,geochemistry,and the Hfisotopes of zircon from the southeastern Sabah gabbro and granite,in this study,the tectonic properties of the Sabah area during the Triassic were investigated.The weighted average U-Pb zircon ages of the gabbro and granite samples were determined to be(230.9±2.5)Ma and(207.1±3.3)Ma,respectively.The granite had SiO_(2) contents of 66.54%-79.47%,low TiO_(2) contents of 0.08%-0.3%,Al_(2)O_(3) contents of 10.97%-16.22%,Na_(2)O contents of 5.91 %-6.39%,and low K_(2)O contents of 0.15%-0.65%.The chondrite-normalized rare earth element(REE) patterns exhibit light REE enrichment,with right-sloping curves.The primitive mantle-normalized trace element spider diagrams exhibit Th,U,La,Sr,and Zr enrichment and Nb,Ta,P and Ti depletions,i.e.,the geochemical characteristics of typical island arc igneous rocks.The tectonic discriminant diagram indicates that the granite is a volcanic arc granite.The Hf isotopic an alysis of gabbro zircon revealed that the zircons have ε_(Hf)(t)values of 12.08-16.24(mean of 14.32) and two-stage model ages(t_(DM2)) of 223-491 Ma(mean of 347 Ma).This indicates that the diagenetic magma of the gabbro was mainly derived from melting of newly formed crustal materials.The ophiolite in southeast Sabah has existed since the early Late Triassic.The crystalline basement granite in southeastern S abah was emplaced lasted from late Triassic to early Cretaceous.Based on previous studies and global plate reconstruction models,it is speculated that the southeastern Sabah granite may have been formed in an island arc setting,i.e.,where the oceanic crust of the Paleo-Tethys Ocean collided with the oceanic crust of the Panthalassa Ocean. 展开更多
关键词 SABAH early late Triassic OPHIOLITE granite tectonic properties
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Effects of soil crust on the collapsing erosion of colluvial deposits with granite residual soil
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作者 LIU Weiping ZENG Bohan +1 位作者 WANG Tianhuan DUAN Junyi 《Journal of Mountain Science》 SCIE CSCD 2024年第8期2579-2591,共13页
Collapsing erosion is a unique phenomenon commonly observed on the granite residue hillslopes in the tropical and subtropical regions of southern China,characterized by its abrupt occurrence and significant erosion vo... Collapsing erosion is a unique phenomenon commonly observed on the granite residue hillslopes in the tropical and subtropical regions of southern China,characterized by its abrupt occurrence and significant erosion volumes.However,the impacts of soil crust conditions on the erosion of colluvial deposits with granite residual soils have only been studied to a limited extent.To address this issue,this study investigates the impacts of three soil crust conditions(i.e.,without crust,10-minute crust,and 20-minute crust)on gully morphology,rainfall infiltration,and runoff and sediment yield during slope erosion of colluvial deposits with granite residues(classified as Acrisols)in Yudu County,Ganzhou City,Jiangxi Province,China,using simulated rainfall tests and photographic methods.The results showed that as the strength of the soil crust increased,the capacity of moisture infiltration and the width and depth of the gully as well as the sediment concentration and yield ratio decreased;at the same time,the runoff ratio increased.The sediment yield in the without-crust test was found to be 1.24 and 1.43 times higher than that observed in the 10-minute crust and 20-minute crust tests,respectively.These results indicate that soil crusts can effectively prevent slope erosion and moisture infiltration,while providing valuable insights for the management of soil erosion in natural environments. 展开更多
关键词 granite residual soil Colluvial deposits Slope erosion Soil crust Sediment yield
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Petrogenesis and Tectonic Implications of the Early Triassic Nianzi Adakitic Granite Unit in the Yanshan Fold and Thrust Belt:New Constraints from U-Pb Geochronology and Sr-Nd-Hf Isotopes
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作者 ZHANG Huijun WU Chu +5 位作者 HE Fubing WANG Biren CUI Yubin LIU Zhenghua YOU Shina DONG Jing 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2024年第1期50-66,共17页
The Nianzi granite unit,which includes the Nianzi,Xiaolianghou and Xiawopu granitic intrusions,is a significant component of the northern part of the North China Craton(NCC)and is situated in the Yanshan fold and thru... The Nianzi granite unit,which includes the Nianzi,Xiaolianghou and Xiawopu granitic intrusions,is a significant component of the northern part of the North China Craton(NCC)and is situated in the Yanshan fold and thrust belt(YFTB).However,there is still debate regarding the tectonic evolutionary history of the YFTB during the late Permian to Triassic period,specifically regarding the timing of subduction and collision between the NCC and the Paleo-Asian Ocean.The Nianzi granite unit exhibits unique petrological,geochronological and geochemical signatures that shed light on the tectonic evolutionary history of the YFTB.This study presents detailed petrology,whole-rock geochemistry,together with Sr-Nd isotopic,zircon U-Pb dating and Lu-Hf isotopic data of the granites within the Nianzi granite unit.Our findings demonstrate that the granites primarily consist of subhedral K-feldspar,plagioclase,quartz,minor biotite and hornblende,with accessory titanite,apatite,magnetite and zircon.Zircon U-Pb dating indicates that the Xiaolianghou granite was emplaced at 247.5±0.62 Ma.Additionally,the adakitic characteristics of the Nianzi,Xiawopu and Xiaolianghou granitic intrusions,such as high Sr and Ba contents and high ratios of Sr/Y and(La/Yb)N,combined with negative Sr-Nd and Lu-Hf isotopes(87Sr/86Sr)i=0.705681–0.7057433,εNd(t)=−21.98 to−20.97,zirconεHf(t)=−20.26 to−9.92,as well as the I-type granite features of high SiO_(2),Na_(2)O and K_(2)O/Na_(2)O ratios,enriched Rb,K,Sr and Ba,along with depleted Th,U,Nb,Ta,P and Ti,suggest that the Nianzi granitic unit was mainly derived from the partial melting of a thickened lower crust containing hydrous,calc-alkaline to high-K calc-alkaline,mafic to intermediate metamorphic rocks.In light of these parameters,we further integrate our data with previous studies and conclude that the Nianzi granitic unit was generated in a post-collisional extensional environment during the Early Triassic. 展开更多
关键词 tectonic evolution zircon geochronology Sr-Nd-Hf isotopes Nianzi granite unit Yanshan fold and thrust belt
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Mechanical properties and fracture surface roughness of thermally damaged granite under dynamic splitting
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作者 Yijin Qian Peng Jia +1 位作者 Songze Mao Jialiang Lu 《Deep Underground Science and Engineering》 2024年第1期103-116,共14页
In order to understand the mechanical properties and the fracture surface roughness characteristics of thermally damaged granite under dynamic splitting,dynamic Brazilian splitting tests were conducted on granite samp... In order to understand the mechanical properties and the fracture surface roughness characteristics of thermally damaged granite under dynamic splitting,dynamic Brazilian splitting tests were conducted on granite samples after thermal treatment at 25,200,400,and 600℃.Results show that the dynamic peak splitting strength of thermally damaged granite samples increases with increasing strain rate,showing obvious strain‐rate sensitivity.With increasing temperature,thermally induced cracks in granite transform from intergranular cracks to intragranular cracks,and to a transgranular crack network.Thermally induced damages reduce the dynamic peak splitting strength and the maximum absorbed energy while increasing the peak radial strain.The fracture mode of the thermally damaged granite under dynamic loads is mode Ⅱ splitting failure.By using the axial roughness index Z2 a,the distribution ranges of the wedge‐shaped failure zones and the tensile failure zones in the fracture surfaces under dynamic Brazilian splitting can be effectively identified.The radial roughness index Z_(2)^(r)is sensitive to the strain rate and temperature.It shows a linear correlation with the peak splitting strength and the maximum absorbed energy and a linear negative correlation with the peak radial strain.Z_(2)^(r)can be used to quantitatively estimate the dynamic parameters based on the models proposed. 展开更多
关键词 dynamic splitting fracture surface roughness granite strain rate thermal treatment
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Geochemistry of Micas from Issia Granite Complexe: A Marker of Geodynamic Evolution
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作者 Koffi Joseph Brou Alain Nicaise Kouamelan Koffi Raoul Teha 《Open Journal of Geology》 CAS 2024年第8期787-804,共18页
The granites and pegmatites located in the southern part of the Issia region, near the columbo-tantaliferous placers, are characterized by the presence of rare metals such as beryl, lithium and Nb-Ta oxides. They main... The granites and pegmatites located in the southern part of the Issia region, near the columbo-tantaliferous placers, are characterized by the presence of rare metals such as beryl, lithium and Nb-Ta oxides. They mainly consist of micas, quartz, plagioclase and potassium feldspar. The work carried out on the micas of these granites and pegmatites (EPMA analyses) has provided new geochemical data contributing to the understanding of the magmatic evolution of the Issia granite complex. Mineralogically, the most evolved G3 granites are characterized by their abundance of muscovite compared to biotite and the presence of pegmatite veins. Geochemically, the muscovites of the G1 and G2 granites are more ferriferous than those of the G3 granites, however, the latter display higher Na contents than the G2 and G3. The muscovites of the granites show an evolution from the pure muscovite series to the zinnwaldite series (micas of the pegmatites) which are lithium-bearing micas. The mineralogical and chemical data of the micas show that they are S-type peraluminous granites and demonstrate the formation of granites and pegmatites through fractional crystallization of the same parental magma. 展开更多
关键词 G3 granites Peraluminous granites Rare Metals Fractional Crystallization
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Early Permian A-type Granites in the Zhangdaqi Area, Inner Mongolia, China and Their Tectonic Implications
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作者 ZHANG Li LIU Yongjiang +10 位作者 SHAO Jun LI Weimin LIANG Chenyue CHANG Ruihong YANG Hongzhi FENG Zhiqiang ZHANG Chao XU Jia SHI Yi YANG Fan HE Pengfei 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2019年第5期1300-1316,共17页
There is a controversy regarding the amalgamation of Xing’an and Songnen Blocks along the Hegenshan-Heihe Suture(HHS)in the eastern Central Asian Orogenic Belt(CAOB).To solve this problem,we performed detailed study ... There is a controversy regarding the amalgamation of Xing’an and Songnen Blocks along the Hegenshan-Heihe Suture(HHS)in the eastern Central Asian Orogenic Belt(CAOB).To solve this problem,we performed detailed study on the granites from the Zhangdaqi area,adjacent to the north of the HHS in the northern part of the Great Xing’an Range,NE China.Geochemically,the granites in the study area are metaluminous-weak peraluminous and high-K calc-alkaline series.Trace elements of the granites show that LREEs are relatively enriched,while HREEs are relatively deficient and obvious REE fractionation.The granites are characterized by obvious negative Eu anomalies,meanwhile,they are relatively enriched in Rb,K,Th and depleted in Ba,Nb,Sr,P,Ti.All the geochemical features suggest that the granites in the Zhangdaqi area are aluminum A-type granites.The zircon LA-ICP-MS U-Pb ages of these granites are 294-298 Ma,indicating that they formed in the Early Permian.These granites also have positiveεHf(t)values(8.4-14.2)and a relatively young two-stage model age between 449 Ma and 977 Ma,implying that the magma was derived from the re-melting of the Early Paleozoic-Neoproterozoic juvenile crust.Combined with geochemical characteristics(Nb/Ta ratios of 9.0-22.2,and Zr/Hf ratios of 52.3-152.0),we believe that the magmatic source area is a mixture of partial melting of the lower crust and depleted mantle.A-type granites and bimodal volcanic rocks along the Hegenshan-Heihe Suture formed during the Late Carboniferous-Early Permian,indicating that the HHS between Xing’an and Songnen Blocks closed in the late EarlyCarboniferous.Subsequently,the Zhangdaqi area was in a post-orogenic extensional environment from Late Carboniferous to Early Permian and resulted in the formation of the A-type granites. 展开更多
关键词 Central Asian OROGENIC Belt Hegenshan-Heihe SUTURE A-TYPE graniteS zircon U-Pb age LU-HF isotopic NE China
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Investigation of granite failure precursor under axial load using modified LSTM framework
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作者 WANG Ya-lei XU Jin-ming 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第8期2930-2943,共14页
Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the v... Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the video camera was used to record the deformation and failure process of rock.The distribution of meso-components in video images was then identified.The meso-components of rock failure precursors were also discussed.Moreover,a modified LSTM(long short-term memory method)based on SSA(sparrow search algorithm)was proposed to estimate the change of meso-components of rock failure precursor.It shows that the initiation and expansion of cracks are mainly caused by feldspar and quartz fracture,and when the quartz and feldspar exit the stress framework,rock failure occurs;the second large increase of crack area and the second large decrease of quartz or feldspar area may be used as a precursor of rock failure;the precursor time of rock failure based on meso-scopic components is about 4 s earlier than that observed by the naked eye;the modified LSTM network has the strongest estimation ability for quartz area change,followed by feldspar and biotite,and has the worst estimation ability for cracks;when using the modified LSTM network to predict the precursors of rock instability and failure,quartz and feldspar could be given priority.The results presented herein may provide reference in the investigation of rock failure mechanism. 展开更多
关键词 granite failure precursor axial load modified long short-term memory method
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Unconfined compressive strength and failure behaviour of completely weathered granite from a fault zone
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作者 DU Shaohua MA Jinyin +1 位作者 MA Liyao ZHAO Yaqian 《Journal of Mountain Science》 SCIE CSCD 2024年第6期2140-2158,共19页
Understanding the strength characteristics and deformation behaviour of the tunnel surrounding rock in a fault zone is significant for tunnel stability evaluation.In this study,a series of unconfined compression tests... Understanding the strength characteristics and deformation behaviour of the tunnel surrounding rock in a fault zone is significant for tunnel stability evaluation.In this study,a series of unconfined compression tests were conducted to investigate the mechanical characteristics and failure behaviour of completely weathered granite(CWG)from a fault zone,considering with height-diameter(h/d)ratio,dry densities(ρd)and moisture contents(ω).Based on the experimental results,a regression mathematical model of unconfined compressive strength(UCS)for CWG was developed using the Multiple Nonlinear Regression method(MNLR).The research results indicated that the UCS of the specimen with a h/d ratio of 0.6 decreased with the increase ofω.When the h/d ratio increased to 1.0,the UCS increasedωwith up to 10.5%and then decreased.Increasingρd is conducive to the improvement of the UCS at anyω.The deformation and rupture process as well as final failure modes of the specimen are controlled by h/d ratio,ρd andω,and the h/d ratio is the dominant factor affecting the final failure mode,followed byωandρd.The specimens with different h/d ratio exhibited completely different fracture mode,i.e.,typical splitting failure(h/d=0.6)and shear failure(h/d=1.0).By comparing the experimental results,this regression model for predicting UCS is accurate and reliable,and the h/d ratio is the dominant factor affecting the UCS of CWG,followed byρd and thenω.These findings provide important references for maintenance of the tunnel crossing other fault fractured zones,especially at low confining pressure or unconfined condition. 展开更多
关键词 Fault fracture zone Completely weathered granite(CWG) Unconfined compression strength(UCS) Multiple nonlinear regression model
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Spatial-temporal distribution and geochemistry of highly evolved Mesozoic granites in Great Xing’an Range,NE China:Discriminant criteria and geological significance
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作者 WU Haoran YANG Hao +4 位作者 GE Wenchun JI Zheng DONG Yu JING Yan JING Jiahao 《Global Geology》 2024年第1期20-34,共15页
Highly evolved granite is an important sign of the mature continent crust and closely associated with deposits of rare metals.In this work,the authors undertake systematically zircon U-Pb ages and whole rock elemental... Highly evolved granite is an important sign of the mature continent crust and closely associated with deposits of rare metals.In this work,the authors undertake systematically zircon U-Pb ages and whole rock elemental data for highly evolved granitic intrusions from the Great Xing’an Range(GXR),NE China,to elucidate their discriminant criteria,spatial-temporal distribution,differentiation and geodynamic mecha-nism.Geochemical data of these highly evolved granites suggest that high w(SiO_(2))(>70%)and differentiation index(DI>88)could be quantified indicators,while strong Eu depletion,high TE_(1,3),lowΣREE and low Zr/Hf,Nb/Ta,K/Rb could only be qualitative indicators.Zircon U-Pb ages suggest that the highly evolved gran-ites in the GXR were mainly formed in Late Mesozoic,which can be divided into two major stages:Late Ju-rassic-early Early Cretaceous(162-136 Ma,peak at 138 Ma),and late Early Cretaceous(136-106 Ma,peak at 126 Ma).The highly evolved granites are mainly distributed in the central-southern GXR,and display a weakly trend of getting younger from northwest to southeast,meanwhile indicating the metallogenic potential of rare metals within the central GXR.The spatial-temporal distribution,combined with regional geological data,indicates the highly evolved Mesozoic granites in the GXR were emplaced in an extensional environ-ment,of which the Late Jurassic-early Early Cretaceous extension was related to the closure of the Mongol-Okhotsk Ocean and roll-back of the Paleo-Pacific Plate,while the late Early Cretaceous extension was mainly related to the roll-back of the Paleo-Pacific Plate. 展开更多
关键词 highly evolved granite Great Xingan Range spatial-temporal distribution extensional environment
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Cu-Bearing Mokama Granite Prospect of the Kibara Belt in the Maniema Province, DRC: A Preliminary Petrography, Geochemistry, and Fluid Inclusion Study
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作者 Douxdoux Kumakele Makutu Ivan Bongwe +3 位作者 Chris Musomo Mfumu Frederick Makoka Mwanza Jean-Pierre Bulambo Pierre Kambuli Kaseti 《Open Journal of Geology》 2023年第10期1007-1023,共17页
The Mokama granites are located in the Kibara belt (KIB) and hosts tin oxide group minerals (TOGM: Sn-W), and sulfide group minerals (SGM: Cu-Zn-Fe-As). The essential of Cu mineralization (non-economic deposit) is dis... The Mokama granites are located in the Kibara belt (KIB) and hosts tin oxide group minerals (TOGM: Sn-W), and sulfide group minerals (SGM: Cu-Zn-Fe-As). The essential of Cu mineralization (non-economic deposit) is disseminated inside the rock and consists of minerals (Raman, EPMA and metallographic microscopy) including chalcopyrite and bornite that are replaced by chalcocite and covellite, and the last also replaced later by malachite. The chemistry (XRF, LA-ICP-MS) of these peraluminous S-type leucogranites show SiO<sub>2</sub> (71 wt% - 79 wt%), ASI (1.4 - 3.1 molar), and are enriched in Rb (681 - 1000 ppm), Ta (12–151 ppm), Sn (43 - 142 ppm), Cu (10 - 4300 ppm), Zn (60 - 740 ppm), U (2.2 - 20.7 ppm) while depleted in Zr (20 - 31 ppm), Sr (20 - 69 ppm), Hf (1.3 - 2.0 ppm), Th (2.2 - 18.9 ppm), W (9 - 113 ppm), Pb (5 - 50 ppm), Ge (5 - 10 ppm), Cs (21 - 53 ppm) and Bi (0.6 - 17.4 ppm) and low ratios of (La/Yb) N, (Gd/Yb) N, (La/Sm) N). Fluid inclusion assemblages (FIAs) hosted in quartz in the Mokama granites show ranges of salinities of 4 - 23 wt% (NaCl equivalent) and homogenization temperatures (Th) of 190°C - 550°C. A boiling assemblage in the granite suggests a fluid phase separation occurred at about 380 - 610 bars, and this corresponds to apparent paleodepths of approximately 1 - 2 km (lithostatic model) or 3 - 5 km (hydrostatic model). FIAs hosted in TOGM such as cassiterite (salinities of 2 wt% - 10 wt% and Th of 220°C - 340°C) helped set up the possible temperature limit of SGM (Cu sulfide) precipitations that are estimated below 200°C. 展开更多
关键词 Mokama granites PETROGRAPHY GEOCHEMISTRY Cu-Mineralization XRF EPMA LA-ICP-MS Fluid Inclusion Microthermometry
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Neoarchean granite-greenstone belts and related ore mineralization in the North China Craton:An overview 被引量:12
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作者 Li Tang M.Santosh 《Geoscience Frontiers》 SCIE CAS CSCD 2018年第3期751-768,共18页
Tectonic processes involving amalgamations of microblocks along zones of ocean closure represented by granite-greenstone belts(GGB) were fundamental in building the Earth's early continents. The crustal growth and... Tectonic processes involving amalgamations of microblocks along zones of ocean closure represented by granite-greenstone belts(GGB) were fundamental in building the Earth's early continents. The crustal growth and cratonization of the North China Craton(NCC) are correlated to the amalgamation of microblocks welded by 2.75-2.6 Ga and ~2.5 Ga GGBs. The lithological assemblages in the GGBs are broadly represented by volcano-sedimentary sequences, subduction-collision related granitoids and bimodal volcanic rocks(basalt and dacite) interlayered with minor komatiites and calc-alkalic volcanic rocks(basalt, andesite and felsic rock). The geochemical features of meta-basalts in the major GGBs of the NCC display affinity with N-MORB, E-MORB, OIB and calc-alkaline basalt, suggesting that the microblocks were separated by oceanic realm. The granitoid rocks display arc signature with enrichment of LILE(K,Rb, Sr, Ba) and LREE, and depletion of HFSE(Nb, Ta, Th, U, Ti) and HREE, and fall in the VAG field. The major mineralization includes Neoarchean BIF-type iron and VMS-type Cu-Zb deposits and these,together with the associated supracrustal rocks possibly formed in back-arc basins or arc-related oceanic slab subduction setting with or without input from mantle plumes. The 2.75-2.60 Ga TTG rocks,komatiites, meta-basalts and metasedimentary rocks in the Yanlingguan GGB are correlated to the upwelling mantle plume with eruption close to the continental margin within an ocean basin. The volcanosedimentary rocks and granitoid rocks in the late Neoarchean GGBs display formation ages of 2.60-2.48 Ga, followed by metamorphism at 2.52-2.47 Ga, corresponding to a typical modern-style subduction-collision system operating at the dawn of Proterozoic. The late Neoarchean komatiite(Dongwufenzi GGB), sanukitoid(Dongwufenzi GGB and Western Shandong GGB), BIF(Zunhua GGB) and VMS deposit(Hongtoushan-Qingyuan-Helong GGB) have closer connection to a combined process of oceanic slab subduction and mantle plume. The Neoarchean cratonization of the NCC appears to have involved two stages of tectonic process along the 2.75-2.6 Ga GGB and ~2.5 Ga GGBs, the former involve plume-arc interaction process, and the latter involving oceanic lithospheric subduction, with or without arcplume interaction. 展开更多
关键词 North China CRATON granite GREENSTONE belt NEOARCHEAN Plate and plume TECTONICS METALLOGENY
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