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
The Indosinian post-collisional Wulong pluton intruded into the Mesoproterozoic Fuping Group, South Qinling, central China. In the southern part of the pluton, some mafic enclaves have sharp or gradational contact rel...The Indosinian post-collisional Wulong pluton intruded into the Mesoproterozoic Fuping Group, South Qinling, central China. In the southern part of the pluton, some mafic enclaves have sharp or gradational contact relationships with the host biotite granodiorite. Geochemistry, zircon LA-ICP MS (laser ablation inductively-coupled plasma mass spectrometry) U-Pb chronology and Sr- Nd-Pb isotope geochemistry of the pluton are reported in this paper. The biotite granodiorite shows close compositional similarities to high-silica adakite. Its chondrite-normalized REE patterns are characterized by strong HREE depletion (Yb = 0.33--0.96 10-6 and Y = 4.77-11.19 ×10^-6), enrichment of Ba (775-1386 x 10-6) and Sr (643-1115 × 10^-6) and high Sr/Y (57.83-159.99) and Y/Yb (10.99-14.32) ratios, as well as insignificant Eu anomalies (6Eu = 0.70-0.83), suggesting a feldspar-poor, garnet±amphibole-rich residual mineral assemblage. The mafic enclaves have higher MgO (4.15- 8.13%), Cr (14.79-371.31 × 10-6), Ni (20.00-224.24× 10^-6) and Nb/Ta (15.42-21.91) than the host granodiorite, implying that they are mantle-derived and might represent underplated mafic magma. Zircon LA-ICP MS dating of the granodiorite yields a ^206pb/^238U weighted mean age of 208±2 Ma (MSWD=0.50, 1σ), which is the age of emplacement of the host biotite granodiorite. This age indicates that the Wulong pluton formed during the late-orogenic or post-collisional stage (〈242±21 Ma) of the South Qinling belt. The host biotite granodiorite displays ^87Sr/^86Sr = 0.7059-0.7062, Isr = 0.7044-- 0.7050,^143Nd/^144Nd = 0.51236-0.51238, εNd(t)= -2.26 to -2.66 to ^206Pb/^204pb = 18.099-18.209, ^207pb/^204pb = 15.873-15.979 and ^208pb/^204pb = 38.973-39.430. Those ratios are similar to those of the Mesoproterozoic Yaolinghe Group in the South Qinling. Furthermore, its Nd isotopic model age (-1.02 Ga) is consistent with the age (-1.1 Ga) of the Yaolinghe Group. Based on the integrated geological and geochemical studies, coupled with previous studies, the authors suggest that the Wulong adakitic biotite granodiorite was probably generated by dehydration melting of the Yaolinghe Group-like thickened mafic crust, triggered by underplating of mafic magma at the boundary of the thickened mafic crust and hot lithospheric mantle, and that the Wulong adakitic biotite granodiorite may have resulted from thinning and delamination of the lower crust or breakoff of the subducting slab of the Mianlue ocean during the Indosinian post-collisional orogenic stage of the Qinling orogenic belt.展开更多
The Jiang Tso ophiolite, situated in the middle segment of the Bangong- Nujiang Suture Zone, is a part of the easternmost Qieli Lake ophiolite subzone and is close to the south of Pung Lake ophiolite. The rock associa...The Jiang Tso ophiolite, situated in the middle segment of the Bangong- Nujiang Suture Zone, is a part of the easternmost Qieli Lake ophiolite subzone and is close to the south of Pung Lake ophiolite. The rock association of Jiang Tso ophiolite is relatively complete and is mainly composed of metamorphic peridotite, gabbro and diabase. Comparing with N-MORB, the ophiolite is high in Mg and low in Ti, K, Na, P, and is depleted in Nb, Ta, Hf, Th and enriched in Rb, Sr and Ba. Geochemical characteristics of the Jiang Tso ophiolite indicate it is of a supra-subduction zone type formed in the spreading ridge of back arc basin. The SHRIMP U-Pb dating of zircons from the gabbro yielded a weighted average age of 188.1±4.1 Ma (MSWD=1.4), indicating the Jiang Tso ophiolite was formed in the late stage of early Jurassic. The Sr, Nd isotopic compositions show that the Tethyan mantle domain is the depleted mantle (DM), with enriched mantle domain II (EMII). They have the same Sr, Nd isotopic composition with the India Ocean MORB type.展开更多
The magma source,petrogenesis,tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area,East Junggar,have thus far not been well-constrained.A better understanding of ...The magma source,petrogenesis,tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area,East Junggar,have thus far not been well-constrained.A better understanding of these issues will help to reveal the magmatic processes and continental growth of Central Asia.The A-type granites in Zhaheba include the Ashutasi alkaline granites and the Yuyitasi syenogranites,which were emplaced at 321.5±4.8 Ma and 321.7±0.6 Ma,respectively.The major rock-forming minerals are orthoclase,perthite,arfvedsonite and quartz,which exhibit the following principal geochemical characteristics of A2-type granites.(1)Their REE distribution curves each exhibit a‘V’-shaped pattern and a marked depletion in Eu.They are rich in large-ion lithophile elements Rb,Th and U as well as high-field-strength elements Nb,Ta,Zr and Hf,but significantly depleted in Ba,Sr,P and Ti.(2)Their(^(87)Sr/^(86)Sr)i values(0.7021-0.7041),εNd(t)values(4.57-5.16)and REE distribution patterns are in basic agreement with those of the Kalamaili A-type granite belt in East Junggar.The T DM2 values of the alkaline granites and syenogranites range from 661 to 709 Ma.The A-type granites may be the products of upwelling asthenosphere-triggered partial melting of immature lower crust.The alkaline granites were late-stage products of crystallization and differentiation.Compared to the syenogranites,the alkaline granites are significantly lower in K_(2)O,Na_(2)O,Al_(2)O 3,FeO,MgO and CaO,but significantly higher in incompatible elements(e.g.,SiO_(2),Rb,and Sr).The magmatic crystallization temperatures of the syenogranites and alkaline granites are 874℃ and 819℃,respectively.As their age gradually decreases(peak ages:322 Ma and 307 Ma,respectively),there is a gradual decrease in the T_(DM2)of the A-type granites and a gradual increase in theεNd(t)value from the Ulungur belt to the Kalamaili belt in East Junggar.The study of A-type granites is therefore one of the keys to understanding the laws and mechanisms of crustal accretion during the Phanerozoic period,as well as also being of great significance for understanding the Paleozoic accretion.展开更多
Studies in the northern South China Sea(SCS)basement remain important for understanding the evolution of the Southeast Asian continental margin.Due to a thick cover of sediments and scarce borehole penetration,little ...Studies in the northern South China Sea(SCS)basement remain important for understanding the evolution of the Southeast Asian continental margin.Due to a thick cover of sediments and scarce borehole penetration,little is known about the age and tectonic affinity of this basement.In this study,an integrated study of zircon U-Pb geochronology,Hf isotopes,and whole-rock major and trace elements on seven basement granitoids from seven boreholes of Qiongdongnan Basin has been carried out.New zircon U-Pb results for these granitoids present middle-late Permian((270.0±1.2)Ma;(253±3.4)Ma),middle to late Triassic((246.2±3.4)Ma;(239.3±0.96)Ma;(237.9±0.99)Ma;(228.9±1.0)Ma)and Late Cretaceous ages((120.6±0.6)Ma).New data from this study,in combination with the previous dataset,indicates that granitoid ages in northern SCS basement vary from 270 Ma to 70.5 Ma,with three age groups of 270–196 Ma,162–142 Ma,and 137–71 Ma,respectively.Except for the late Paleozoic-Mesozoic rocks in the basement of the northern SCS,a few old zircon grains with the age of(2708.1±17)Ma to(2166.6±19)Ma provide clues to the existence of the pre-Proterozoic components.The geochemical signatures indicate that the middle Permian-early Cretaceous granitoids from the Qiongdongnan Basin are I-type granites formed in a volcanic arc environment,which were probably related to the subduction of the Paleo-Pacific Plate.展开更多
We report the oxide,element geochemistry and Nd isotopic geochemical data of apatite in the middle Pleistocene medium-and fine-grained trachyte in the Tianchi volcanic area(TVA)of Changbai Mountain,discussing the rela...We report the oxide,element geochemistry and Nd isotopic geochemical data of apatite in the middle Pleistocene medium-and fine-grained trachyte in the Tianchi volcanic area(TVA)of Changbai Mountain,discussing the relationship between apatite and the composition of the whole rock.The purpose is to use the apatite geochemical data to constrain the evolutionary process of trachytic magma and the petrogenesis of trachyte in the cone-forming period of the Tianchi volcano.Apatite(Ca_(5)(PO_(4))_(3)(OH,F,Cl))is a common accessory mineral that occurs widely in volcanic rocks in the TVA.The apatites in the trachyte are mainly subhedral-anhedral,having the characteristics of magmatic apatite.In terms of oxide and element geochemistry,they have homogeneous Al_(2)O_(3),SiO_(2),MgO,P_(2)O_(5),K_(2)O,CaO and heterogeneous TiO2,with high F content.They are generally enriched in Th,U and LREEs,depleted in Nb,Ta,Zr,Hf and HFSEs,showing negative Ba,Sr and Ti anomalies,similar to those of the whole-rock host trachytes.The ratios of high(La/Yb)_(N),low δEu(Eu/Eu*),Sr/Y value and ΣREE content in apatite,and the F,Sr,Y,Th/U,La/Sm,and Nd/Tb with ΣREE andδEu anomalies showed a linear correlation,all of those indicating that the host magma has the characteristic of high differentiation.The apatite grains generally having ^(147)Sm/^(144)Nd,^(143)Nd/^(144)Nd ratios and ε_(Nd)(t)values of 0.1072-0.1195,0.5123-0.5126 and -3.49 to -0.10,respectively,are similiar to those of the host rock.The Nd model ages TDM1 are 949-803 Ma in apatite.Combined with theεNd(t)value of the apatite core(-7.06 to-3.49),we conclude that the initial magma of the host trachyte was derived from the partial melting of Proterozoic crustal material and there was an assimilation of wall rocks during its evolution.展开更多
The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of flu...The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of fluorite 2,and barite 2 with calcite and minor quartz and sulfides.The Merguechoum ore deposits have never been investigated.This study was the first contribution that studied the genesis of fluorite and barite.The ore occurs as dissemination within granite intrusion and also fills the NE-SWtrending meter-sized fractures and faults.The values of the total Rare Earth Elements and Yttrium(REY)and the ratios of LREY/HREY,Y/Ho,Tb/Ca,and Tb/La indicate that the Merguechoum fluorite precipitated from hydrothermal fluids,likely basinal brines,which interacted with the Hercynian granite.The REY data indicate that the ore-forming fluids of the early stage have intensely interacted with the Hercynian granite compared to those of the late ore stage.The gradual decrease in the europium(Eu/Eu^(*)),yttrium(Y/Y^(*)),and cerium(Ce/Ce^(*))anomalies and a low concentration ofΣREY observed in the second ore stage compared to the first ore stage suggest an increase in p H and fO_(2)and by inference a decrease in temperature during the evolution of the hydrothermal system.This evolution could be explained by fluid mixing between the ascending basinal hydrothermal fluids and the diluted sulfate-rich meteoric water barite separates from selected samples reveal that the dissolved sulfates(SO_(4)^(2-))were derived from Permian–Triassic sulfates and/or coeval poreseawater sulfates.The proposed fluid mixing triggered the precipitation of an early-stage F-Ba assemblage followed by the second-stage F-Ba mineralization.Geologic fieldwork,REY inventories,and isotope data point to the ore genesis during the Permian–Triassic extensional tectonic activity concerning the Pangea rifting.This extensional tectonic environment is likely the driving force that mobilized a large amount of the ore-forming basinal brines along the available faults and fractures to the loci of ore deposition.展开更多
The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb+Zn reserves of more than 5 million ton...The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb+Zn reserves of more than 5 million tons at Pb+Zn grade of higher than 25%and contains abundant associated metals,such as Ag,Ge,Cd,and Ga.The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield.Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types,namely lumpy,patch and vein calcites in accordance with their occurrence.There is not intercalated contact between calcite and ore minerals and among the three types of calcite,indicating that they are the same ore-forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element(REE) and C-O isotopic compositions of calcites in the Huize Pb-Zn deposits.From lumpy to patch to vein calcites,REE contents decrease as LREE/ HREE ratios increase.The chondrite-normalized REE patterns of the three types of calcites are characterized by LREE-rich shaped,in which the lumpy calcite shows(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〈1,the patch calcite has(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〉1,and the vein calcite displays(La)_N〉(Ce)_N〉(Pr)_N〉(Nd)_N with Eu/Eu~*〉1.The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield.Theδ^(13) C_(PDb) andδ^(18)O_(Smow) values of the three types of calcites vary from-3.5‰to-2.1‰and 16.7‰to 18.6‰,respectively,falling within a small field between primary mantle and marine carbonate in theδ^(13)C_(PDb) vsδ^(18)O_(Smow) diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages.The ore-forming fluids of the deposits resulted from crustal -mantle mixing processes,in which the mantle-derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts,and the crustal fluid was mainly provided by carbonate strata in the orefield.The ore-forming fluids in the deposits were homogenized before mineralization,and the ore-forming environment varied from relatively reducing to oxidizing.展开更多
The Tuolugou cobalt deposit is the first independent large-scale Co- and Au-bearing deposit discovered in northwestern China. It is located in the eastern Kunlun orogenic belt in Qinghai Province, and occurs conformab...The Tuolugou cobalt deposit is the first independent large-scale Co- and Au-bearing deposit discovered in northwestern China. It is located in the eastern Kunlun orogenic belt in Qinghai Province, and occurs conformably in low-grade metamorphic volcano-sedimentary rock series with well-developed Na-rich hydrothermal sedimentary rocks and typical hydrothermal sedimentary ore fabrics. Fluid inclusions and isotopic geochemistry studies suggest that cobalt mineralizing fluid is dominated by NaCI-H20 system, accompanied by NaCI-CO2-H20-N2 system responsible for gold mineralization. Massive, banded and disseminated pyrite ores have similar compositions of He and Ar isotopes from the mineralizing fluid, with 3He/4He range between 0.10 to 0.31Ra (averaging 0.21Ra), and 4~Ar/36Ar between 302 and 569 (averaging 373), which reflects that Co mineralizing fluids derived dominantly from meteoric water deeply circulating. ~34S values of pyrite approaches to zero (~34S ranging from -4.5%o to +1.5%o, centering around -1.8%o to -0.2%o), reflecting its deep source. Ore lead is characterized by distinctly high radiogenesis, with 2~6pb/2~4pb〉19.279, 2~7pb/2~4pb〉15.691 and 2~spb/2~4pb〉39.627, and its values show an increase trend from country rocks, regional Paleozoic volcanic rocks to ores. This may have suggested that high radiogentic ore Pb derived mainly from country rocks by leaching meteoric water-dominated hydrothermal fluid during its circulation at depth. Cobalt occurs mainly in sulfide phase (such as pyrite), but cobalt enrichment, and presence and increasing contents of Co-bearing minerals have a positive correlation with metamorphic degree. The Tuolugou deposit and other typical strata-bound Co-Cu-Au deposits have striking similarities in the geological features and metallogenic pattern of primary cobalt. All of them are syngenetic hydrothermal exhalative sedimentation in origin.展开更多
According to the age measurements of single zircon evaporation method, combined with the study of Nd isotopic geochemistry in Tongbai area, the protolith age of basic granulites is about 1 010 Ma; the protolith ag...According to the age measurements of single zircon evaporation method, combined with the study of Nd isotopic geochemistry in Tongbai area, the protolith age of basic granulites is about 1 010 Ma; the protolith age of intermediate acid granulites is probably more than 904 Ma, which is close to the age of the basic granulites. The basic granulites would be the nature occurrence of basic magma underplating beneath the base of lower crust in the North Qinling crustal vertical growth event at about 1 000 Ma. However, the intermediate acid granulites were the result of the mixing fusion between the lower crust material and the underplating basic magma, which shows a strong crust mantle interaction. The 470-480 Ma are the peak metamorphic ages of the basic and intermediate acid granulites, which related to the crust bi direction shortening and crust thickening due to the Erlangping back arc basin southward subduction and the paleo Qinling oceanic plate northward subduction.展开更多
South Qinling Tectonic Belt(SQTB)is located between the Shangzhou-Danfeng and Mianxian-Lueyang sutures.There are a lot of early Mesozoic granitoid plutons in its middle segment, comprising the Dongjiangkou-Zhashui g...South Qinling Tectonic Belt(SQTB)is located between the Shangzhou-Danfeng and Mianxian-Lueyang sutures.There are a lot of early Mesozoic granitoid plutons in its middle segment, comprising the Dongjiangkou-Zhashui granitoid plutons at the northeast,Huayang-Wulong-Laocheng granitoid plutons at the central part,Xiba granitoid pluton at the northwest and Guangtoushan-Liuba granitoid plutons at the southwest.These Indonisian granitoids contain a mass of various scale mafic enclaves,which show sometimes clear boundaries and sometimes transitional boundaries with their host granitoids.These granitoids also exhibit metaluminous to peraluminous series,commonly higher Mg# and a wide range of petrochemistry from low-K tholeiite series,through mid-K and high-K calc-alkaline series to shoshonite series and predominated samples are attributed to mid-K and high-K calc-alkaline series.Detailed analyses in Sr-Nd isotopic systematics and petrochemistry reveal that there may be regionally initial granitoid magma of the Indonisian granitoid plutons,comprising Dongjiangkou-Zhashui,Huayang-Wulong-Laocheng,Xiba,and Guangtoushan-Liuba granitoid plutons,which were produced by hybrids of magmas in various degrees,and the initial magmas were derived from both the mantle and the lower continental crust(LCC)sources in the SQTB.The initial granitoid magma further did the magma hybrid with the magmas from the LCC,crystallization fractionation,and assimilation with upper crustal materials during their emplacement to produce these granitoid plutons in the SQTB.These magmatism processes are most likely to occur under continent marginal arc and syn-collision to post-collision tectonic backgrounds.展开更多
In this paper we report geochemical and Nd-Sr isotopic data for a late Archean gneissic granitic pluton (Hengling pluton), an early Paleoproterozoic complex (Xipan complex) and a late Paleoproterozoic granitic plu...In this paper we report geochemical and Nd-Sr isotopic data for a late Archean gneissic granitic pluton (Hengling pluton), an early Paleoproterozoic complex (Xipan complex) and a late Paleoproterozoic granitic pluton (Yunzhongshan granites) from the Liiliang-Wutai terrain, North China, to trace the source of these late Archean-Paleoproterozoic granitoids and, particularly, to understand the nature and mechanism of continental growth at that time. The Hengling granitic gneisses (ca. 2.51 Ga) are characterized by high Na2O and LILEs, TTG-like REE patterns (highly depleted HREE and minor Eu anomalies) and moderately depleted Nd-Sr isotopic compositions (εNd(t) =1.2-2.7, ISr=0.7015-0.7019), and were considered as being products of arc magmatism that was developed upon the North China craton. The Xipan complex (ca. 2.2 Ga) contain gabbroic diorite and monzonite, mostly being Na2O-rich, highly fractionated REE patterns and isotopically enriched (εNd(t) =-1.5 to -4.1, Isr=0.7038-0.706). The gabbroic diorites probably originated from melting of an enriched mantle source, but significantly contaminated by lower crustal material, and the monzonites probably represent a product of a mixture between the gabbroic dioritic magma and granitic melts of crustal origin. The Yunzhongshan post-collisional granitoids (ca. 1.8 Ga) are characterized by high-K affinity and highly-enriched and homogeneous Nd isotopic compositions (εNd(t)=-4.9 to -5.7), although they split into two groups in terms of REE patterns: one group showing elevated HREE (and Sc, Y and Zr) with significant negative Eu anomalies and the other showing highly depleted HREE and, to a lesser extent, mid-REE with negligible Eu anomalies. These granites are genetically related to a process of extensional collapse of a thickened orogen. They formed through magma mixing between mantle-derived basaltic magmas and crust-derived granitic melts, followed by significant fractionation of ferromagnesian phases (like hornblende and Cpx) and feldspar and accessory zircons. Some Yunzhongshan granites show very old Nd model ages (2.9-3.0 Ga), suggesting the existence of continental crust older than 2.7 Ga, which is supported by our zircon Hf isotopic data for these granites.展开更多
The Langdu high-K calc-alkaline intrusions are located in the Zhongdian area, which is the southern part of the Yidun island arc. These intrusive rocks consist mainly of monzonite porphyry, granodiorite, and diorite p...The Langdu high-K calc-alkaline intrusions are located in the Zhongdian area, which is the southern part of the Yidun island arc. These intrusive rocks consist mainly of monzonite porphyry, granodiorite, and diorite porphyry. The K20 content of majority of these rocks is greater than 3%, and, in the K20-SiO2 diagram, all the samples fall into the high-K calc-alkaline to shoshonitic fields. They are enriched in light rare earth elements (LREEs) and depleted in heavy rare earth elements (HREEs; LaN/YbN = 14.3-21.2), and show slightly negative Eu anomalies (6Eu = 0.77-1.00). These rocks have high K, Rb, Sr, and Ba contents; moderate to high enrichment of compatible elements (Cr = 36.7-79.9 ppm, Co = 9.6-16.4 ppm, and MgO = 2.2%-3.4%); low Nb, Ta, and Ti contents, and characteristic of low high field strength elements(HFSEs) versus incompatible elements ratios (Nb/Th = 0.75, Nb/La = 0.34) and incompatible elements ratios (Nb/U = 3.0 and Ce/Pb = 5.1, Ba/Rb = 12.0). These rocks exhibit restricted Sr and Nd isotopic compositions, with (87Sr/S6Sr)i values ranging from 0.7044 to 0.7069 and ENd(t) values from -2.8 to -2.2. The Sr-Nd isotope systematic and specific trace element ratios suggest that Langdu high-K calc-alkaline intrusive rocks derived from a metasomatized mantle source. The unique geochemical feature of intrusive rocks can be modeled successfully using different members of a slightly enriched mantle, a slab-derived fluid, and terrigenous sediments. It can be inferred that the degree of partial melting and the presence of specific components are temporally related to the tectonic evolution of the Zhongdian island arc. Formation of these rocks can be explained by the various degrees of melting within an ascending region of the slightly enriched mantle, triggered by the subduction of the Garz^--Litang ocean, and an interaction between the slab-derived fluid and the terrigenous sediments.展开更多
Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enriches Sr,P,Mn a...Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enriches Sr,P,Mn and Ba, enriches Li,U,Th,Sc,Co,Cu,Pb,Zn,Cr,Rb,Y,Sb and light rare earth elements,slightly enriches V,Ga,Zr,Nb,Cd and middle rare earth elements,is short of Mo,In,Sn,Cs,Hf,Ta,W,Ti,Bi and heavy rare earth elements. The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and selective absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements.The REE (rare earth elements)partition pattern of foraminifera shell of the Okinawa Trough shows enrichment of middle rare earth elements with slightly negative Ce anomaly,which are different from those of foraminifera of the Pacific Ocean.The Sr,Nd isotopic ratios of the Okinawa Trough foraminifera are 0 709 769 and 0 512 162,respectively, which are different not only from those of oceanic water, but also from those of river water of China's Mainland, the former is slightly higher than those of oceanic water,but much lower than those of river water;the latter is slightly lower than those of oceanic water,but higher than those of river water,demonstrating that the Okinawa Trough sea water has been influenced by river water of China's Mainland.展开更多
The Goshgarchay Cu-Au deposit is located in the central part of the northwest flank of the Murovdagh region in the Lesser Caucasus.The Goshgarchay Cu-Au deposit is associated with Middle Jurassic volcanic and Late Jur...The Goshgarchay Cu-Au deposit is located in the central part of the northwest flank of the Murovdagh region in the Lesser Caucasus.The Goshgarchay Cu-Au deposit is associated with Middle Jurassic volcanic and Late Jurassic-Early Cretaceous high-K calc-alkaline intrusive rocks.The Cu-Au mineralization is commonly related to quartz-sericite-chlorite alteration dominantly composed of chalcopyrite,gold,sphalerite,pyrite,bornite,hematite,covellite,chalcocite,malachite,and azurite.The Goshgarchay copper-gold deposit,which is 600 m wide and approximately 1.2 km long,is seen as a faultcontrolled and vein-,stockwork-and disseminated type deposit.The Goshgarchay Cu-Au deposit predominantly comprises Cu(max.64500 ppm)and Au(max.11.3 ppm),while it comprises relatively less amounts Zn(max.437 ppm),Mo(max.47.5 ppm),Pb(max.134 ppm),and Ag(max.21 ppm).The homogenization temperatures and salinities of fluid inclusions in quartz for stage Ⅰ range from 380℃ to 327℃,and 6.9 wt% to 2.6 wt% NaCl eq.,respectively.Thand salinities in quartz for stage Ⅱ range from 304℃ to 253℃,and 7.6 wt% to 3.2 wt% NaCl eq.,respectively.The calculated δ^(34)S_(h2s)values(-1.5‰ to 5.5‰)of sulfides and especially the narrow range of δ^(34)S_(h2s) values of chalcopyrite and bornite(between -0.07‰ and +0.7‰)indicate that the source of the Goshgarchay Cu-Au mineralization is magmatic.Based on the mineralogical,geochemical,fluid inclusion,and sulfur isotopic data,the Goshgarchay Cu-Au deposit represents a late stage peripheral magmatic-hydrothermal mineralization probably underlain by a concealed porphyry deposit.展开更多
The Tianshan Orogen(TO)is one of the largest typical accretionary orogenic belts in the world.Of which,the late Paleozoic was a critical era to understand the tectonic and geodynamic transition from accretion to colli...The Tianshan Orogen(TO)is one of the largest typical accretionary orogenic belts in the world.Of which,the late Paleozoic was a critical era to understand the tectonic and geodynamic transition from accretion to collision.However,the late Paleozoic tectonic evolutionary history,especially for the time of the ocean-continent transition,is still debated although the origin and tectonic settings for the Paleozoic volcanic,felsic igneous magmatism in TO and reginal geology have been done in the last decades.In contrast,the researches on the mafic dykes in TO was not systematically carried out till now.Reginal-scale mafic dykes are commonly regarded as the products created in a extensional setting,and used to identify the major tectonic events such as rifting and continental break-up and further trace the mantle natures and geodynamic mechanism(Halls,1982;Bleeker and Ernst,2006;Li et al.,2008;Ernst et al.,2010;Srivastava,2011;Hou,2012;Peng,2015;Peng et al.,2019).There are widespread late Paleozoic mafic dykes beside the huge of intermediate-acid igneous rocks in the TO,being an idea object to reveal the extensional events,tectonic evolution and the mantle nature and geodynamic processes.We present the ICPMS in situ zircon U–Pb dating,Lu-Hf and whole-rock Sr-Nd isotopes as well as the geochemistry data for these mafic dykes to better constraint their petrogenesis and mantle nature.New zircon U-Pb dating for 12 samples from the representative basic dykes and basalts yield three distinct stages of^332 Ma,316–302 Ma and 288–282 Ma,respectively.In which,the first stage of mafic dykes is mainly occurred in both East Tianshan Orogen(ETO)and West Tianshan Orogen(WTO),and composed of dolerite with minor basalts.The second stage of mafic dyke also can be found in both ETO and WTO.However,in contrast to the first stage of mafic dykes,they have relatively variable rock types from the dolerite/or gabbros to gabbroic diorite.The third stage of mafic dykes are slightly intermediate in composition,and chiefly consist of andesitic-basaltic dolerite with some diorites.They are widely developed not only in both ETO and WTO,but also in the Beishan area to the east of the ETO,indicating a large-scale mafic magmatism in Tianshan and adjacent areas.展开更多
Objective The Ordovician Shaanxi salt basin is located in the junction of the North China Sea and the Qilian Sea.ln this basin the Majiagou Formation accumulated more than 1000m thick evaporite-carbonate sediments, a...Objective The Ordovician Shaanxi salt basin is located in the junction of the North China Sea and the Qilian Sea.ln this basin the Majiagou Formation accumulated more than 1000m thick evaporite-carbonate sediments, and this basin is divided into east and west saltern sags (ESS, WSS) according to the characteristics of geochemical analysis (Zhang Yongsheng et al., 2014). Isotope stratigraphy of evaporite sediments represents a fundamental tool in palaeoenvironmental and palaeoclimate reconstruction. This work first illustrates the stable isotope geochemistry of the Shaanxi evaporites, which represents the most significant example of detailed facies stratigraphy for the Majiagou Formation evaporite-carbonate (M5) in Ordos epicontinental sea (Liu Jingdong et al.,展开更多
基金funded by the National Natural Science Foundation of China (2019M653840XB)the National Natural Science Foundation of China (41972043 and 42062006)。
文摘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.
文摘The Indosinian post-collisional Wulong pluton intruded into the Mesoproterozoic Fuping Group, South Qinling, central China. In the southern part of the pluton, some mafic enclaves have sharp or gradational contact relationships with the host biotite granodiorite. Geochemistry, zircon LA-ICP MS (laser ablation inductively-coupled plasma mass spectrometry) U-Pb chronology and Sr- Nd-Pb isotope geochemistry of the pluton are reported in this paper. The biotite granodiorite shows close compositional similarities to high-silica adakite. Its chondrite-normalized REE patterns are characterized by strong HREE depletion (Yb = 0.33--0.96 10-6 and Y = 4.77-11.19 ×10^-6), enrichment of Ba (775-1386 x 10-6) and Sr (643-1115 × 10^-6) and high Sr/Y (57.83-159.99) and Y/Yb (10.99-14.32) ratios, as well as insignificant Eu anomalies (6Eu = 0.70-0.83), suggesting a feldspar-poor, garnet±amphibole-rich residual mineral assemblage. The mafic enclaves have higher MgO (4.15- 8.13%), Cr (14.79-371.31 × 10-6), Ni (20.00-224.24× 10^-6) and Nb/Ta (15.42-21.91) than the host granodiorite, implying that they are mantle-derived and might represent underplated mafic magma. Zircon LA-ICP MS dating of the granodiorite yields a ^206pb/^238U weighted mean age of 208±2 Ma (MSWD=0.50, 1σ), which is the age of emplacement of the host biotite granodiorite. This age indicates that the Wulong pluton formed during the late-orogenic or post-collisional stage (〈242±21 Ma) of the South Qinling belt. The host biotite granodiorite displays ^87Sr/^86Sr = 0.7059-0.7062, Isr = 0.7044-- 0.7050,^143Nd/^144Nd = 0.51236-0.51238, εNd(t)= -2.26 to -2.66 to ^206Pb/^204pb = 18.099-18.209, ^207pb/^204pb = 15.873-15.979 and ^208pb/^204pb = 38.973-39.430. Those ratios are similar to those of the Mesoproterozoic Yaolinghe Group in the South Qinling. Furthermore, its Nd isotopic model age (-1.02 Ga) is consistent with the age (-1.1 Ga) of the Yaolinghe Group. Based on the integrated geological and geochemical studies, coupled with previous studies, the authors suggest that the Wulong adakitic biotite granodiorite was probably generated by dehydration melting of the Yaolinghe Group-like thickened mafic crust, triggered by underplating of mafic magma at the boundary of the thickened mafic crust and hot lithospheric mantle, and that the Wulong adakitic biotite granodiorite may have resulted from thinning and delamination of the lower crust or breakoff of the subducting slab of the Mianlue ocean during the Indosinian post-collisional orogenic stage of the Qinling orogenic belt.
基金financially supported by the Tibetan special foundation of China Geological Survey (No.1212011221088 and No.1212011221087)Natural Science Foundation of China (No.41372208 and No.41472054)open foundation of State Key Laboratory of Ore Deposit Geochemistry,Chinese Academy of Sciences (No.201304)
文摘The Jiang Tso ophiolite, situated in the middle segment of the Bangong- Nujiang Suture Zone, is a part of the easternmost Qieli Lake ophiolite subzone and is close to the south of Pung Lake ophiolite. The rock association of Jiang Tso ophiolite is relatively complete and is mainly composed of metamorphic peridotite, gabbro and diabase. Comparing with N-MORB, the ophiolite is high in Mg and low in Ti, K, Na, P, and is depleted in Nb, Ta, Hf, Th and enriched in Rb, Sr and Ba. Geochemical characteristics of the Jiang Tso ophiolite indicate it is of a supra-subduction zone type formed in the spreading ridge of back arc basin. The SHRIMP U-Pb dating of zircons from the gabbro yielded a weighted average age of 188.1±4.1 Ma (MSWD=1.4), indicating the Jiang Tso ophiolite was formed in the late stage of early Jurassic. The Sr, Nd isotopic compositions show that the Tethyan mantle domain is the depleted mantle (DM), with enriched mantle domain II (EMII). They have the same Sr, Nd isotopic composition with the India Ocean MORB type.
基金This work was supported by the National Key Research and Development Program of China(2018YFC0604002)the Geological Survey program of China Geological Survey(DD20221643-6)the Fundamental Research Funds of Chinese Academy of Geological Sciences(JKY21021,JKY202122).
文摘The magma source,petrogenesis,tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area,East Junggar,have thus far not been well-constrained.A better understanding of these issues will help to reveal the magmatic processes and continental growth of Central Asia.The A-type granites in Zhaheba include the Ashutasi alkaline granites and the Yuyitasi syenogranites,which were emplaced at 321.5±4.8 Ma and 321.7±0.6 Ma,respectively.The major rock-forming minerals are orthoclase,perthite,arfvedsonite and quartz,which exhibit the following principal geochemical characteristics of A2-type granites.(1)Their REE distribution curves each exhibit a‘V’-shaped pattern and a marked depletion in Eu.They are rich in large-ion lithophile elements Rb,Th and U as well as high-field-strength elements Nb,Ta,Zr and Hf,but significantly depleted in Ba,Sr,P and Ti.(2)Their(^(87)Sr/^(86)Sr)i values(0.7021-0.7041),εNd(t)values(4.57-5.16)and REE distribution patterns are in basic agreement with those of the Kalamaili A-type granite belt in East Junggar.The T DM2 values of the alkaline granites and syenogranites range from 661 to 709 Ma.The A-type granites may be the products of upwelling asthenosphere-triggered partial melting of immature lower crust.The alkaline granites were late-stage products of crystallization and differentiation.Compared to the syenogranites,the alkaline granites are significantly lower in K_(2)O,Na_(2)O,Al_(2)O 3,FeO,MgO and CaO,but significantly higher in incompatible elements(e.g.,SiO_(2),Rb,and Sr).The magmatic crystallization temperatures of the syenogranites and alkaline granites are 874℃ and 819℃,respectively.As their age gradually decreases(peak ages:322 Ma and 307 Ma,respectively),there is a gradual decrease in the T_(DM2)of the A-type granites and a gradual increase in theεNd(t)value from the Ulungur belt to the Kalamaili belt in East Junggar.The study of A-type granites is therefore one of the keys to understanding the laws and mechanisms of crustal accretion during the Phanerozoic period,as well as also being of great significance for understanding the Paleozoic accretion.
基金The National Natural Science Foundation of China under contract No.42072181。
文摘Studies in the northern South China Sea(SCS)basement remain important for understanding the evolution of the Southeast Asian continental margin.Due to a thick cover of sediments and scarce borehole penetration,little is known about the age and tectonic affinity of this basement.In this study,an integrated study of zircon U-Pb geochronology,Hf isotopes,and whole-rock major and trace elements on seven basement granitoids from seven boreholes of Qiongdongnan Basin has been carried out.New zircon U-Pb results for these granitoids present middle-late Permian((270.0±1.2)Ma;(253±3.4)Ma),middle to late Triassic((246.2±3.4)Ma;(239.3±0.96)Ma;(237.9±0.99)Ma;(228.9±1.0)Ma)and Late Cretaceous ages((120.6±0.6)Ma).New data from this study,in combination with the previous dataset,indicates that granitoid ages in northern SCS basement vary from 270 Ma to 70.5 Ma,with three age groups of 270–196 Ma,162–142 Ma,and 137–71 Ma,respectively.Except for the late Paleozoic-Mesozoic rocks in the basement of the northern SCS,a few old zircon grains with the age of(2708.1±17)Ma to(2166.6±19)Ma provide clues to the existence of the pre-Proterozoic components.The geochemical signatures indicate that the middle Permian-early Cretaceous granitoids from the Qiongdongnan Basin are I-type granites formed in a volcanic arc environment,which were probably related to the subduction of the Paleo-Pacific Plate.
基金funded by research on the strategy of Improving the All-for-one Tourism Transportation Capacity of Changbai Mountain and the China Scholarship Council(Grant Nos.JL2021-03 and 202104190014)。
文摘We report the oxide,element geochemistry and Nd isotopic geochemical data of apatite in the middle Pleistocene medium-and fine-grained trachyte in the Tianchi volcanic area(TVA)of Changbai Mountain,discussing the relationship between apatite and the composition of the whole rock.The purpose is to use the apatite geochemical data to constrain the evolutionary process of trachytic magma and the petrogenesis of trachyte in the cone-forming period of the Tianchi volcano.Apatite(Ca_(5)(PO_(4))_(3)(OH,F,Cl))is a common accessory mineral that occurs widely in volcanic rocks in the TVA.The apatites in the trachyte are mainly subhedral-anhedral,having the characteristics of magmatic apatite.In terms of oxide and element geochemistry,they have homogeneous Al_(2)O_(3),SiO_(2),MgO,P_(2)O_(5),K_(2)O,CaO and heterogeneous TiO2,with high F content.They are generally enriched in Th,U and LREEs,depleted in Nb,Ta,Zr,Hf and HFSEs,showing negative Ba,Sr and Ti anomalies,similar to those of the whole-rock host trachytes.The ratios of high(La/Yb)_(N),low δEu(Eu/Eu*),Sr/Y value and ΣREE content in apatite,and the F,Sr,Y,Th/U,La/Sm,and Nd/Tb with ΣREE andδEu anomalies showed a linear correlation,all of those indicating that the host magma has the characteristic of high differentiation.The apatite grains generally having ^(147)Sm/^(144)Nd,^(143)Nd/^(144)Nd ratios and ε_(Nd)(t)values of 0.1072-0.1195,0.5123-0.5126 and -3.49 to -0.10,respectively,are similiar to those of the host rock.The Nd model ages TDM1 are 949-803 Ma in apatite.Combined with theεNd(t)value of the apatite core(-7.06 to-3.49),we conclude that the initial magma of the host trachyte was derived from the partial melting of Proterozoic crustal material and there was an assimilation of wall rocks during its evolution.
文摘The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of fluorite 2,and barite 2 with calcite and minor quartz and sulfides.The Merguechoum ore deposits have never been investigated.This study was the first contribution that studied the genesis of fluorite and barite.The ore occurs as dissemination within granite intrusion and also fills the NE-SWtrending meter-sized fractures and faults.The values of the total Rare Earth Elements and Yttrium(REY)and the ratios of LREY/HREY,Y/Ho,Tb/Ca,and Tb/La indicate that the Merguechoum fluorite precipitated from hydrothermal fluids,likely basinal brines,which interacted with the Hercynian granite.The REY data indicate that the ore-forming fluids of the early stage have intensely interacted with the Hercynian granite compared to those of the late ore stage.The gradual decrease in the europium(Eu/Eu^(*)),yttrium(Y/Y^(*)),and cerium(Ce/Ce^(*))anomalies and a low concentration ofΣREY observed in the second ore stage compared to the first ore stage suggest an increase in p H and fO_(2)and by inference a decrease in temperature during the evolution of the hydrothermal system.This evolution could be explained by fluid mixing between the ascending basinal hydrothermal fluids and the diluted sulfate-rich meteoric water barite separates from selected samples reveal that the dissolved sulfates(SO_(4)^(2-))were derived from Permian–Triassic sulfates and/or coeval poreseawater sulfates.The proposed fluid mixing triggered the precipitation of an early-stage F-Ba assemblage followed by the second-stage F-Ba mineralization.Geologic fieldwork,REY inventories,and isotope data point to the ore genesis during the Permian–Triassic extensional tectonic activity concerning the Pangea rifting.This extensional tectonic environment is likely the driving force that mobilized a large amount of the ore-forming basinal brines along the available faults and fractures to the loci of ore deposition.
基金jointly by National Basic Research Program of China(973 Program) (2007CB411402)the Knowledge innovation project of Chinese Academy of Sciences(KZCX2-YW-Q04-05, KZCX2-YW-111-03)the National Natural Science Foundation of China(No.40573036).
文摘The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb+Zn reserves of more than 5 million tons at Pb+Zn grade of higher than 25%and contains abundant associated metals,such as Ag,Ge,Cd,and Ga.The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield.Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types,namely lumpy,patch and vein calcites in accordance with their occurrence.There is not intercalated contact between calcite and ore minerals and among the three types of calcite,indicating that they are the same ore-forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element(REE) and C-O isotopic compositions of calcites in the Huize Pb-Zn deposits.From lumpy to patch to vein calcites,REE contents decrease as LREE/ HREE ratios increase.The chondrite-normalized REE patterns of the three types of calcites are characterized by LREE-rich shaped,in which the lumpy calcite shows(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〈1,the patch calcite has(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〉1,and the vein calcite displays(La)_N〉(Ce)_N〉(Pr)_N〉(Nd)_N with Eu/Eu~*〉1.The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield.Theδ^(13) C_(PDb) andδ^(18)O_(Smow) values of the three types of calcites vary from-3.5‰to-2.1‰and 16.7‰to 18.6‰,respectively,falling within a small field between primary mantle and marine carbonate in theδ^(13)C_(PDb) vsδ^(18)O_(Smow) diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages.The ore-forming fluids of the deposits resulted from crustal -mantle mixing processes,in which the mantle-derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts,and the crustal fluid was mainly provided by carbonate strata in the orefield.The ore-forming fluids in the deposits were homogenized before mineralization,and the ore-forming environment varied from relatively reducing to oxidizing.
基金supported by grant no K090 1 from the Scientific Research Fund of the China Central Non-Commercial Institutethe Program of Excellent Young Scientists from the Ministry of Land and Resources(200809)+1 种基金grant No40302019 from the National Natural Science Foundation of ChinaGeological Survey Program Grant 1212011085528 from the China Geological Survey
文摘The Tuolugou cobalt deposit is the first independent large-scale Co- and Au-bearing deposit discovered in northwestern China. It is located in the eastern Kunlun orogenic belt in Qinghai Province, and occurs conformably in low-grade metamorphic volcano-sedimentary rock series with well-developed Na-rich hydrothermal sedimentary rocks and typical hydrothermal sedimentary ore fabrics. Fluid inclusions and isotopic geochemistry studies suggest that cobalt mineralizing fluid is dominated by NaCI-H20 system, accompanied by NaCI-CO2-H20-N2 system responsible for gold mineralization. Massive, banded and disseminated pyrite ores have similar compositions of He and Ar isotopes from the mineralizing fluid, with 3He/4He range between 0.10 to 0.31Ra (averaging 0.21Ra), and 4~Ar/36Ar between 302 and 569 (averaging 373), which reflects that Co mineralizing fluids derived dominantly from meteoric water deeply circulating. ~34S values of pyrite approaches to zero (~34S ranging from -4.5%o to +1.5%o, centering around -1.8%o to -0.2%o), reflecting its deep source. Ore lead is characterized by distinctly high radiogenesis, with 2~6pb/2~4pb〉19.279, 2~7pb/2~4pb〉15.691 and 2~spb/2~4pb〉39.627, and its values show an increase trend from country rocks, regional Paleozoic volcanic rocks to ores. This may have suggested that high radiogentic ore Pb derived mainly from country rocks by leaching meteoric water-dominated hydrothermal fluid during its circulation at depth. Cobalt occurs mainly in sulfide phase (such as pyrite), but cobalt enrichment, and presence and increasing contents of Co-bearing minerals have a positive correlation with metamorphic degree. The Tuolugou deposit and other typical strata-bound Co-Cu-Au deposits have striking similarities in the geological features and metallogenic pattern of primary cobalt. All of them are syngenetic hydrothermal exhalative sedimentation in origin.
文摘According to the age measurements of single zircon evaporation method, combined with the study of Nd isotopic geochemistry in Tongbai area, the protolith age of basic granulites is about 1 010 Ma; the protolith age of intermediate acid granulites is probably more than 904 Ma, which is close to the age of the basic granulites. The basic granulites would be the nature occurrence of basic magma underplating beneath the base of lower crust in the North Qinling crustal vertical growth event at about 1 000 Ma. However, the intermediate acid granulites were the result of the mixing fusion between the lower crust material and the underplating basic magma, which shows a strong crust mantle interaction. The 470-480 Ma are the peak metamorphic ages of the basic and intermediate acid granulites, which related to the crust bi direction shortening and crust thickening due to the Erlangping back arc basin southward subduction and the paleo Qinling oceanic plate northward subduction.
基金provided by the National Scientific and Tecnological Support Program of China(Grant No:2006BAB01A11)
文摘South Qinling Tectonic Belt(SQTB)is located between the Shangzhou-Danfeng and Mianxian-Lueyang sutures.There are a lot of early Mesozoic granitoid plutons in its middle segment, comprising the Dongjiangkou-Zhashui granitoid plutons at the northeast,Huayang-Wulong-Laocheng granitoid plutons at the central part,Xiba granitoid pluton at the northwest and Guangtoushan-Liuba granitoid plutons at the southwest.These Indonisian granitoids contain a mass of various scale mafic enclaves,which show sometimes clear boundaries and sometimes transitional boundaries with their host granitoids.These granitoids also exhibit metaluminous to peraluminous series,commonly higher Mg# and a wide range of petrochemistry from low-K tholeiite series,through mid-K and high-K calc-alkaline series to shoshonite series and predominated samples are attributed to mid-K and high-K calc-alkaline series.Detailed analyses in Sr-Nd isotopic systematics and petrochemistry reveal that there may be regionally initial granitoid magma of the Indonisian granitoid plutons,comprising Dongjiangkou-Zhashui,Huayang-Wulong-Laocheng,Xiba,and Guangtoushan-Liuba granitoid plutons,which were produced by hybrids of magmas in various degrees,and the initial magmas were derived from both the mantle and the lower continental crust(LCC)sources in the SQTB.The initial granitoid magma further did the magma hybrid with the magmas from the LCC,crystallization fractionation,and assimilation with upper crustal materials during their emplacement to produce these granitoid plutons in the SQTB.These magmatism processes are most likely to occur under continent marginal arc and syn-collision to post-collision tectonic backgrounds.
基金This study is financially supported by the National Natural Science Foundation of China (No. 40420120135).
文摘In this paper we report geochemical and Nd-Sr isotopic data for a late Archean gneissic granitic pluton (Hengling pluton), an early Paleoproterozoic complex (Xipan complex) and a late Paleoproterozoic granitic pluton (Yunzhongshan granites) from the Liiliang-Wutai terrain, North China, to trace the source of these late Archean-Paleoproterozoic granitoids and, particularly, to understand the nature and mechanism of continental growth at that time. The Hengling granitic gneisses (ca. 2.51 Ga) are characterized by high Na2O and LILEs, TTG-like REE patterns (highly depleted HREE and minor Eu anomalies) and moderately depleted Nd-Sr isotopic compositions (εNd(t) =1.2-2.7, ISr=0.7015-0.7019), and were considered as being products of arc magmatism that was developed upon the North China craton. The Xipan complex (ca. 2.2 Ga) contain gabbroic diorite and monzonite, mostly being Na2O-rich, highly fractionated REE patterns and isotopically enriched (εNd(t) =-1.5 to -4.1, Isr=0.7038-0.706). The gabbroic diorites probably originated from melting of an enriched mantle source, but significantly contaminated by lower crustal material, and the monzonites probably represent a product of a mixture between the gabbroic dioritic magma and granitic melts of crustal origin. The Yunzhongshan post-collisional granitoids (ca. 1.8 Ga) are characterized by high-K affinity and highly-enriched and homogeneous Nd isotopic compositions (εNd(t)=-4.9 to -5.7), although they split into two groups in terms of REE patterns: one group showing elevated HREE (and Sc, Y and Zr) with significant negative Eu anomalies and the other showing highly depleted HREE and, to a lesser extent, mid-REE with negligible Eu anomalies. These granites are genetically related to a process of extensional collapse of a thickened orogen. They formed through magma mixing between mantle-derived basaltic magmas and crust-derived granitic melts, followed by significant fractionation of ferromagnesian phases (like hornblende and Cpx) and feldspar and accessory zircons. Some Yunzhongshan granites show very old Nd model ages (2.9-3.0 Ga), suggesting the existence of continental crust older than 2.7 Ga, which is supported by our zircon Hf isotopic data for these granites.
基金supported by the National Science Foundation of China (NSFC) project(41203039)the innovation team of ore-forming dynamics and prediction of concealed deposits, KMUST(2008)
文摘The Langdu high-K calc-alkaline intrusions are located in the Zhongdian area, which is the southern part of the Yidun island arc. These intrusive rocks consist mainly of monzonite porphyry, granodiorite, and diorite porphyry. The K20 content of majority of these rocks is greater than 3%, and, in the K20-SiO2 diagram, all the samples fall into the high-K calc-alkaline to shoshonitic fields. They are enriched in light rare earth elements (LREEs) and depleted in heavy rare earth elements (HREEs; LaN/YbN = 14.3-21.2), and show slightly negative Eu anomalies (6Eu = 0.77-1.00). These rocks have high K, Rb, Sr, and Ba contents; moderate to high enrichment of compatible elements (Cr = 36.7-79.9 ppm, Co = 9.6-16.4 ppm, and MgO = 2.2%-3.4%); low Nb, Ta, and Ti contents, and characteristic of low high field strength elements(HFSEs) versus incompatible elements ratios (Nb/Th = 0.75, Nb/La = 0.34) and incompatible elements ratios (Nb/U = 3.0 and Ce/Pb = 5.1, Ba/Rb = 12.0). These rocks exhibit restricted Sr and Nd isotopic compositions, with (87Sr/S6Sr)i values ranging from 0.7044 to 0.7069 and ENd(t) values from -2.8 to -2.2. The Sr-Nd isotope systematic and specific trace element ratios suggest that Langdu high-K calc-alkaline intrusive rocks derived from a metasomatized mantle source. The unique geochemical feature of intrusive rocks can be modeled successfully using different members of a slightly enriched mantle, a slab-derived fluid, and terrigenous sediments. It can be inferred that the degree of partial melting and the presence of specific components are temporally related to the tectonic evolution of the Zhongdian island arc. Formation of these rocks can be explained by the various degrees of melting within an ascending region of the slightly enriched mantle, triggered by the subduction of the Garz^--Litang ocean, and an interaction between the slab-derived fluid and the terrigenous sediments.
文摘Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments. The foraminifera shell from the Okinawa Trough strongly enriches Sr,P,Mn and Ba, enriches Li,U,Th,Sc,Co,Cu,Pb,Zn,Cr,Rb,Y,Sb and light rare earth elements,slightly enriches V,Ga,Zr,Nb,Cd and middle rare earth elements,is short of Mo,In,Sn,Cs,Hf,Ta,W,Ti,Bi and heavy rare earth elements. The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and selective absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements.The REE (rare earth elements)partition pattern of foraminifera shell of the Okinawa Trough shows enrichment of middle rare earth elements with slightly negative Ce anomaly,which are different from those of foraminifera of the Pacific Ocean.The Sr,Nd isotopic ratios of the Okinawa Trough foraminifera are 0 709 769 and 0 512 162,respectively, which are different not only from those of oceanic water, but also from those of river water of China's Mainland, the former is slightly higher than those of oceanic water,but much lower than those of river water;the latter is slightly lower than those of oceanic water,but higher than those of river water,demonstrating that the Okinawa Trough sea water has been influenced by river water of China's Mainland.
基金financially supported by the Scientific Research Project Coordination of Konya Technical University(Grant No.211007014)。
文摘The Goshgarchay Cu-Au deposit is located in the central part of the northwest flank of the Murovdagh region in the Lesser Caucasus.The Goshgarchay Cu-Au deposit is associated with Middle Jurassic volcanic and Late Jurassic-Early Cretaceous high-K calc-alkaline intrusive rocks.The Cu-Au mineralization is commonly related to quartz-sericite-chlorite alteration dominantly composed of chalcopyrite,gold,sphalerite,pyrite,bornite,hematite,covellite,chalcocite,malachite,and azurite.The Goshgarchay copper-gold deposit,which is 600 m wide and approximately 1.2 km long,is seen as a faultcontrolled and vein-,stockwork-and disseminated type deposit.The Goshgarchay Cu-Au deposit predominantly comprises Cu(max.64500 ppm)and Au(max.11.3 ppm),while it comprises relatively less amounts Zn(max.437 ppm),Mo(max.47.5 ppm),Pb(max.134 ppm),and Ag(max.21 ppm).The homogenization temperatures and salinities of fluid inclusions in quartz for stage Ⅰ range from 380℃ to 327℃,and 6.9 wt% to 2.6 wt% NaCl eq.,respectively.Thand salinities in quartz for stage Ⅱ range from 304℃ to 253℃,and 7.6 wt% to 3.2 wt% NaCl eq.,respectively.The calculated δ^(34)S_(h2s)values(-1.5‰ to 5.5‰)of sulfides and especially the narrow range of δ^(34)S_(h2s) values of chalcopyrite and bornite(between -0.07‰ and +0.7‰)indicate that the source of the Goshgarchay Cu-Au mineralization is magmatic.Based on the mineralogical,geochemical,fluid inclusion,and sulfur isotopic data,the Goshgarchay Cu-Au deposit represents a late stage peripheral magmatic-hydrothermal mineralization probably underlain by a concealed porphyry deposit.
基金co-funded by the Land and Resources Survey Project of China(Grant no.12120113042200)National Natural Science Foundation of China(41421002)the MOST Special Fund from State Key Laboratory of Continental Dynamics,Northwest University(201210133)
文摘The Tianshan Orogen(TO)is one of the largest typical accretionary orogenic belts in the world.Of which,the late Paleozoic was a critical era to understand the tectonic and geodynamic transition from accretion to collision.However,the late Paleozoic tectonic evolutionary history,especially for the time of the ocean-continent transition,is still debated although the origin and tectonic settings for the Paleozoic volcanic,felsic igneous magmatism in TO and reginal geology have been done in the last decades.In contrast,the researches on the mafic dykes in TO was not systematically carried out till now.Reginal-scale mafic dykes are commonly regarded as the products created in a extensional setting,and used to identify the major tectonic events such as rifting and continental break-up and further trace the mantle natures and geodynamic mechanism(Halls,1982;Bleeker and Ernst,2006;Li et al.,2008;Ernst et al.,2010;Srivastava,2011;Hou,2012;Peng,2015;Peng et al.,2019).There are widespread late Paleozoic mafic dykes beside the huge of intermediate-acid igneous rocks in the TO,being an idea object to reveal the extensional events,tectonic evolution and the mantle nature and geodynamic processes.We present the ICPMS in situ zircon U–Pb dating,Lu-Hf and whole-rock Sr-Nd isotopes as well as the geochemistry data for these mafic dykes to better constraint their petrogenesis and mantle nature.New zircon U-Pb dating for 12 samples from the representative basic dykes and basalts yield three distinct stages of^332 Ma,316–302 Ma and 288–282 Ma,respectively.In which,the first stage of mafic dykes is mainly occurred in both East Tianshan Orogen(ETO)and West Tianshan Orogen(WTO),and composed of dolerite with minor basalts.The second stage of mafic dyke also can be found in both ETO and WTO.However,in contrast to the first stage of mafic dykes,they have relatively variable rock types from the dolerite/or gabbros to gabbroic diorite.The third stage of mafic dykes are slightly intermediate in composition,and chiefly consist of andesitic-basaltic dolerite with some diorites.They are widely developed not only in both ETO and WTO,but also in the Beishan area to the east of the ETO,indicating a large-scale mafic magmatism in Tianshan and adjacent areas.
基金This work was funded by the National Key R&D Program of China(grant No.2017YFC0602806)Geological Survey Project of China Geological Survey(grant No.121201103000150011 and 121201103000168508)Open Project of State Key Laboratory of Resource and Prospecting(grant No.PRP/open-1308)
文摘Objective The Ordovician Shaanxi salt basin is located in the junction of the North China Sea and the Qilian Sea.ln this basin the Majiagou Formation accumulated more than 1000m thick evaporite-carbonate sediments, and this basin is divided into east and west saltern sags (ESS, WSS) according to the characteristics of geochemical analysis (Zhang Yongsheng et al., 2014). Isotope stratigraphy of evaporite sediments represents a fundamental tool in palaeoenvironmental and palaeoclimate reconstruction. This work first illustrates the stable isotope geochemistry of the Shaanxi evaporites, which represents the most significant example of detailed facies stratigraphy for the Majiagou Formation evaporite-carbonate (M5) in Ordos epicontinental sea (Liu Jingdong et al.,