Following the researches of helium isotopic compositions in mantle-derived xenoliths in eastern China, this study reported noble gas abundances and isotopic compositions of mantle-derived xenoliths from Kuandian of Li...Following the researches of helium isotopic compositions in mantle-derived xenoliths in eastern China, this study reported noble gas abundances and isotopic compositions of mantle-derived xenoliths from Kuandian of Liaoning Province, Huinan of Jilin Province and Hannuoba of Hebei Province. Compared with the middle ocean ridge basalt (MORB) and other continental areas, mantle-derived xenoliths in NE China are characterized by slightly low noble gas abundances, 3He/4He equivalent to or lower than that of MORB, 40Ar/36Ar lower than that of MORB, 38Ar/36Ar and Ne-Kr-Xe isotopic ratios equivalent to those of atmosphere. These results indicate the heterogeneity of subcontinental lithospheric mantle beneath northeastern China, that is, a MORB reservoir-like mantle beneath Kuandian and an enriched/metasomatized mantle beneath Huinan. Low 40Ar/ 36Ar ratios in the three studied areas may imply that a subducted atmospheric component has been preserved in the subcontinental lithospheric mantle.展开更多
This paper deals with the chemical and isotopic compositions of escaped gases from the Rehai geothermal area in Tengchong county of Yunnan Province. Results indicate that there is the mantle-derived magmatic intrusion...This paper deals with the chemical and isotopic compositions of escaped gases from the Rehai geothermal area in Tengchong county of Yunnan Province. Results indicate that there is the mantle-derived magmatic intrusion in shallow crust at this area. Modern mantle-derived mag-matic volatiles are being released currently in a steady stream by way of active faults. The escaped gases are mostly composed of CO2, together with subordinate amounts of H2S, N2, H2, CH4, SO2, CO and He. At the studied area, the north-south directed fault is the deepest, and it may be interlinked with the deep-seated thermal reservoir that would be directly recharged by the mantle-derived magmatic volatile. The He, C isotopic evidence reveals that the modern active magma beneath Rehai area may originate from the historical mantle-derived magma which caused the latest eruptive activity of volcanoes in that region.展开更多
This paper presents systematic studies on the C-O and Sr-Nd isotopic compositions for Cretaceous Badou carbonatites, Fangcheng basalts, and Jiaodong lamprophyres and Paleozoic Mengyin kimberlites in Shandong Province,...This paper presents systematic studies on the C-O and Sr-Nd isotopic compositions for Cretaceous Badou carbonatites, Fangcheng basalts, and Jiaodong lamprophyres and Paleozoic Mengyin kimberlites in Shandong Province, China. Paleozoic kimberlites have normal and uniform C-O isotopic compositions with δ13C and δ18O in the range of -4.8‰--7.6‰ and +9.9‰-+13.2‰, respectively. However, Cretaceous three different types of mantle-derived rocks have quite different C-O isotopic compositions, indicating that the mantle sources are probably partially contaminated with organic carbon-bearing crustal materials. These Cretaceous rocks show uniform and EMII-like Sr-Nd isotopic compositions and also indicate that the mantle sources were affected by recycled crustal materials. Comparative studies of C-O and Sr-Nd isotopes reveal that the lithospheric mantle beneath the eastern North China Craton had different isotope characteristics in the Paleozoic, the early Cretaceous, and the Tertiary time. This demonstrates that the lithospheric mantle beneath the region underwent at least twice reconstructions since the Paleozoic. Available data imply that the first reconstruction mainly happened during the Triassic-Jurassic time with gradual changes and the second in the Cretaceous with abrupt changes. Results also show that the early Cretaceous (especially at 120-130 Ma) was perhaps the key period leading to the dramatic change of the Mesozoic geodynamics on the eastern North China Craton.展开更多
Commercial accumulation of mantle-derived helium in the sedimentary shell is discussed. Generally speaking, a commercial helium pool is formed by accumulated 4He that comes from uranium and thorium via a-decay; theref...Commercial accumulation of mantle-derived helium in the sedimentary shell is discussed. Generally speaking, a commercial helium pool is formed by accumulated 4He that comes from uranium and thorium via a-decay; therefore, it has a very low He/4He value in the magnitude of 10 . The helium concentration in some gas wells of eastern China oil/gas provinces is about or over 0.05%-0.1%, consequently forming commercial helium wells (pools), such as the Wangjinta Gas Pool in Songliao Basin, Huangqiao Gas Pool in North Jiangsu Basin and some gas wells in Sanshui Basin. Studies have proved that when the 3He/4He value of a helium gas pool is about 3.7×10 -6 -7.2× 10-6, namely mantle-derived helium in its total helium concentration accounts for 33. 5%-65.4%, it is a crust-mantle dual-source or dominantly mantle-derived helium gas pool, which is a novel helium resource and its formation is mainly related to the distribution of megafractures.展开更多
Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of ...Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of a mantle component throughout the island, which has been highly diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium is high in the northern island （12%-16% of total He） and gradually decreases towards southern coast （1%-3% of total He）. Such a distribution pattern is most likely controlled by the Pleocene-Quaternary volcanic activities in the northern island and groundwater circulation along the deep major faults. The 4~Ar/36Ar and N2/Ar ratios suggest that N2 and Ar of the hot spring gases are mostly meteoric. Although 13C values of CO2 （-20%0 to -27%0） with low concentrations are consistent with the biogenic origin, the combination of SHe/4He and 51SCco2 suggests a two end-member mixing of mantle and crustal components with CO2/3He ratios of 2x 109 and 8 1011, respectively. However, the low CO2/3He ratios （1- 22106） can not be ascribed in terms of the simple mixing but has to be explained by the addition of radiogenic 4He and loss of CO2 by calcite precipitation in the hydrothermal system, which is most likely controlled by the degree of gas-water-rock interaction.展开更多
The 187Os/ 188Os ratios of spinel lherzolite xenoliths from Panshishan determined with N-TIMS are lower than that of the primitive mantle, which shows depleted mantle characteristics. Their positive correlation with A...The 187Os/ 188Os ratios of spinel lherzolite xenoliths from Panshishan determined with N-TIMS are lower than that of the primitive mantle, which shows depleted mantle characteristics. Their positive correlation with Al-2O-3/MgO suggests that the geochemical behavior of trace elements Re and Os is similar to that of Al-2O-3 and MgO respectively during the magmatic evolution and Re-Os isotopic system is largely immune to mantle metasomatism. A model age of 2 8-3 4 Ga obtained by 187Os/ 188Os-Al-2O-3/MgO correlation might represent the homogeneous age of the mantle lithosphere beneath the area.展开更多
On the basis of the chemical components and stable isotopic compositions of escaped gases from the Tianchi volcanic geothermal area, the material sources of these gases are discussed, presenting that they are mainly d...On the basis of the chemical components and stable isotopic compositions of escaped gases from the Tianchi volcanic geothermal area, the material sources of these gases are discussed, presenting that they are mainly derived from the residual mantle-derived magma in the crust; Changbai geothermal area may be directly interlinked with the eruption canal in history; there is a stable reservoir of the geothermal water and the deep-seated gases under the Changbai geothermal area, with water temperature of the reservoir being about (166±9)℃.展开更多
Fluids and noble gases of mantle-derived materials are important tracers forthe mantle information. Compositions of primary fluids and noble gases in mantle-derived mineralsfrom the Yishu area, Shandong Province, Chin...Fluids and noble gases of mantle-derived materials are important tracers forthe mantle information. Compositions of primary fluids and noble gases in mantle-derived mineralsfrom the Yishu area, Shandong Province, China, were tested by the methods of heat-bursting andheat-melting respectively. The fluids are mainly composed of CO_2, CO and H_2, which account forabout 90% of the total, and are similar to the mantle-derived rocks from other areas of easternChina; ratios of ~3He/~4He in almost all samples range from 0.82 Ra to 2.74 Ra, whereas^(40)Ar/^(36)Ar from 299.5 to 758.8. Both ranges are much lower than those of the typical oceanmantle-derived samples (such as MORB) and primarily reflect the influences of the atmosphericcomponents and the radiogenic isotopes. Ratios of C/~3He range from 27.6 x 10~9 to 1050 x 10~9,N_2/Ar from 927 to 56612, and N_2/~3He from 2.5 x 10~9 to 27 x 10~9, similar to those in westernUnited States and New Zealand which belong to the tectonic plate collision regions. The ratios fallin the intersect of mantle-crust-atmosphere in the comprehensive tracer-charts, reflecting theinfluences of the atmosphere and the crusts with organic components. Our results suggest that thecomposition of the primary fluids and the isotopic ratios of the noble gases may either reflect theevolution process of mantle-derived rocks connected with the rise and eruption of magma, or theinfluence of the ancient subduction-plate on the continental mantle of this region.展开更多
There are four deposit types related to a Permian mafic complex in northern Xinjiang, i.e., copper-nickel sulfide deposit, vanadic titanomagnetite deposit, magnetite （-cobalt） deposit and Cu-Ni- VTiFe composite depo...There are four deposit types related to a Permian mafic complex in northern Xinjiang, i.e., copper-nickel sulfide deposit, vanadic titanomagnetite deposit, magnetite （-cobalt） deposit and Cu-Ni- VTiFe composite deposit. The deposits are distributed spanning tectonic units with close and consecutive metallogenic ages. A transitional deposit type can occur among the end-member deposits. Trace elements of host rocks show that they can derive from similar source area. Hence, they constitute a particular metallogenic series related to a mafic-ultramafic complex that is also a symbol series of the post-collisional stage of the Central Asia Metallogenic Province （CAMP）. The metallogenic ages of the series are between 260 Ma and 300 Ma throughout the Permian. Unlike mineralization from a mantle plume, the metallogenic period of this series spans at least 40 Ma. Compared with related deposits of the Emeishan mantle plume, the North Xinjiang series has a similar ore-forming element assemblage but has preferably developed Cu-Ni sulfide deposits rather than vanadic titanomagnetite deposits. In concomitance with this series, North Xinjiang area has developed a set of syntectonic Au-Cu-Mo metallogenic series related to a felsic volcanic-intrusive complex, which might indicate that there is no direct relationship with mantle plume activity. From early to late, i.e., the sequence of copper-nickel sulfide to magnetite （-cobalt） to vanadic titanomagnetite deposit, the host rock series evolves from mafic-ultramafic and tholeiite series to mafic and alkalic series, the ~REE content tends to increase with increasing of REE fractionation, and some of the trace elements （particularly LIL） also show an increasing tendency. The above evolutionary regularity possibly reflects a course where the magma source deepens and thermal interface moves down, energy gradually exhausts, and neo-continental crust forming in the postcollision stage tends to stabilize.展开更多
Taking the Himalayan granitoids around Kunjirap in the western Qinghai-Tibetplateau as an example, the authors present in this paper the characteristics of the granitoids richin mantle-derived fluid components and dis...Taking the Himalayan granitoids around Kunjirap in the western Qinghai-Tibetplateau as an example, the authors present in this paper the characteristics of the granitoids richin mantle-derived fluid components and discuss their rock-forming mechanism. The research resultsindicate that the rock assemblage of the studied granitoids involves diopside syenite-diopsidegranite-biotite (monzonitic) granite, consisting mainly of K-feldspar, oligoclase, quartz,iron-phlogolite, diopside and edenite. The rocks are rich in mantle-derived fluid components ofvolatiles including F, alkali metal elements such as K, Na, Rb, Sr and Ha, and radiogenicheat-producing elements such as U and Th. They were generated by the influx of mantle-derived fluidsinto the lower crest to give rise to partial melting during the lithosphere thinning in theQinghai-Tibet plateau.展开更多
The Sanshandao Au deposit is located in the famous Sanshandao metallogenic belt,Jiaodong area.To date,accumulative Au resources of 1000 t have been identified from the belt.Sanshandao is a world-class gold deposit wit...The Sanshandao Au deposit is located in the famous Sanshandao metallogenic belt,Jiaodong area.To date,accumulative Au resources of 1000 t have been identified from the belt.Sanshandao is a world-class gold deposit with Au mineralization hosted in Early Cretaceous Guojialing-type granites.Thus,studies on the genesis and ore-forming element sources of the Sanshandao Au deposit are crucial.He and Ar isotopic analyses of fluid inclusions from pyrite(the carrier of Au)indicate that the fluid inclusions have 3 He/4 He=0.043–0.21 Ra with an average of 0.096 Ra and 40 Ar/36 Ar=488–664 with an average of 570.8.These values represent the initial He and Ar isotopic compositions of ore-forming fluids for trapped fluid inclusions.The comparison of H–O isotopic characteristics combined with deposit geology and wall rock alteration reveals that the ore-forming fluids of the Sanshandao Au deposit show mixed crust–mantle origin characteristics,and they mainly comprise crust-derived fluid mixed with minor mantle-derived fluid and meteoric water during the uprising process.The ore-forming elements were generally sourced from pre-Cambrian meta-basement rocks formed by Mesozoic reactivation and mixed with minor shallow crustal and mantle components.展开更多
Lode gold deposits are among the most economically important types of gold deposits in the world.Globally,they formed mainly in three time intervals,2.8 to 2.5 Ga,2.1 to 1.8 Ga,and 700 Ma to the present.Sources of ore...Lode gold deposits are among the most economically important types of gold deposits in the world.Globally,they formed mainly in three time intervals,2.8 to 2.5 Ga,2.1 to 1.8 Ga,and 700 Ma to the present.Sources of ore-forming fluids and other components are of critical importance in a better understanding of the genesis and the geodynamic controls of these deposits.Although ore-forming fluids were mostly derived from devolatization of sedimentary and/or volcanic sequences during greenschist to amphibolite facies metamorphism associated with orogenic deformation,magmatic hydrothermal fluids have been increasingly shown to be important in many gold deposits in various regions.In this review paper,we summarize the major features of lode gold deposits,possible sources of ore-forming fluids,and mechanisms of gold mineralization.While we acknowledge the critical role of metamorphically derived fluids in the genesis of such deposits worldwide,we emphasize that mantle-or basaltic magma-derived fluids may have been much more important than commonly thought.We use the Liaodong peninsula of the North China Craton as an example to demonstrate the significance of mantle-derived fluids.Integrating earlier studies and new data,we show that some of the late Mesozoic lode gold deposits in the North China Craton may have formed from magmatic hydrothermal fluids due to the extension and partial melting of the hydrated,metasomatized subcontinental lithosphere mantle,as best exemplified by the Wulong gold deposit.展开更多
We have analyzed the gold content of 65 samples of mantle-derived xenoliths and their host rocks from eastern China, which is found to be inhomogeneous, falling in the ranges of 1.0×109-8.2×109 (averaging 3....We have analyzed the gold content of 65 samples of mantle-derived xenoliths and their host rocks from eastern China, which is found to be inhomogeneous, falling in the ranges of 1.0×109-8.2×109 (averaging 3.8 ×10-9) and 0.2×10-9-5.3×10-9 (averaging 2.7×10-9) in the mantle-derived xenoliths and the host basalts respectively. Except the samples from Wanquan County of Hebei Province and Anding County of Hainan Province, the gold content is the highest on the margins of the North China platform and decreases spatially towards the north and south, and temporally the samples of the Tertiary have a higher gold content than those of the Quaternary. The gold content of the mantle-derived xenoliths and the host Paleozoic kimberlites is 3.8×10-9-180×109and 0.1×10-9-38.0×10-9 respectively, which are higher than that in the mantle-derived xenoliths in basalt and the host Cenozoic basalts. The mantle-derived xenoliths have a higher gold content than the host rocks, but their relativity is not very clear, suggesting that the genetic relationship between them is complex. Our data indicate that the average gold content of the lithospheric mantle in eastern China is approximately equal to or approaching 3.8×10-9, which is lower than the average abundance of the upper mantle (5.0×10-9), higher than the average abundance of the continental crust (3.0×10-9) and only slightly higher than the average abundance of the lower continental crust (3.4×10-9). Except the samples from Hainan Province, the mantle-derived xenoliths in basalts with a high gold content are distributed on the two margins of the North China platform, corresponding to the gold deposits-concentrated districts in northwest Hebei Province and Shandong Province, showing the control by the old continental lithospheric mantle and the lower continental crust on the margins of the North China platform. The gold content of the mantle-derived xenoliths from Hainan Province ranges from 7.1×10-9 to 15×10-9, suggesting that some blocks of the lithospheric mantle in展开更多
The values of the helium isotopes in the inclusions of the Ordovician reservoir rocks in the Kongxi buried hill belt in the Huanghua depression were first measured and the source of helium and its geological significa...The values of the helium isotopes in the inclusions of the Ordovician reservoir rocks in the Kongxi buried hill belt in the Huanghua depression were first measured and the source of helium and its geological significance were investigated in comparison with those of the helium isotopes in the conclusions in the Ordovician rocks in the Ordos basin and the Tarim basin. The input of the mantle-derived helium into the inclusions in the carbonate reservoir rocks was found from the Konggu 3 well, the Konggu 4 well, and the Konggu 7 well in the Kongxi buried hill belt. The 3He/4He and R/Ra in the conclusions in the Ordovician oil-bearing reservoir rocks in the Konggu 7 well average 2.54×10-6(3) (sample quantity, the same below) and 1.82(3), respectively. The percent of the mantle-derived helium in the inclusions of the reservoir rocks in the Konggu 7 well reaches up to an average of 23.0%(3). The age of the contribution of the mantle-derived helium to the inclusions in the Kongxi buried hill belt is in the Late Triassic or the Early Tertiary. The finding of the mantle-derived helium shows that the interaction of the deep crust with mantle and the activity of deep faults occurred, the terrestrial heat flow value was high, and mantle-derived inorganic gas pools might be formed in the Kongxi buried hill belt. The finding of the mantle-derived helium in the inclusions of oil-bearing reservoir rocks also provides a new way for researching the activity of mantle-derived matter and its associated geological problems.展开更多
Based on summarizing of the effect of mantle-derived fluid on the formation of ores, especially on gold ore, and with the latest investigations, such as the formation of ore from the action of shallow-deep fluid, the ...Based on summarizing of the effect of mantle-derived fluid on the formation of ores, especially on gold ore, and with the latest investigations, such as the formation of ore from the action of shallow-deep fluid, the transportation effect of the thermal energy by mantle-derived fluid, this paper mainly aims at the effect of mantle-derived fluid on the generation of hydrocarbons. With the proof from geochemistry and fluid inclusion, it was suggested that the mantle-derived fluid not only supplied source materials for hydrocarbons, but also supplied essential energy and matter necessary for the generation of hydrocarbons. The mantle-derived fluid had a good effect, but at the same time it had an adverse effect under specific conditions, on the formation of reservoirs. This paper also discusses the future direction and significance of studying mantle-derived fluid.展开更多
This paper deals with deformation textures and fabrics of mantle-derived xenoliths and dislocation microstructures of olivine in the upper mantle in the Penghu Islands, Taiwan. According to the calculation of the chem...This paper deals with deformation textures and fabrics of mantle-derived xenoliths and dislocation microstructures of olivine in the upper mantle in the Penghu Islands, Taiwan. According to the calculation of the chemical composition of xenolith minerals (pyroxene), the equilibrium temperatures and pressures were 986-1116@ and 1.50-2.60 GPa, respectively. Deformation events in the upper mantle may fall into three sequences' (1) uniform steady-state flow deformation with high temperatures and low stresses, (2) shear flow deformation with high temperatures and relatively high stresses on diapiric margins of the upper mantle, and (3) extraction deformation of {110} glide bands with low temperatures and high strain rates. Deformation events and thermal structure of the upper mantle in the study area show that eastern Fujian and the Penghu Islands are characterized by very similar rheological properties of the upper mantle. Volcanism of basalts in the Penghu Islands is related to hot spots of the upper mantle under neath the Taiwan Strait, and diapirism and upwelling of the upper mantle are the dominant factors responsible for rifting of the continental margins in eastern China.展开更多
基金This work was supported by the National Climbing Program (Grant No. 95-P-39).
文摘Following the researches of helium isotopic compositions in mantle-derived xenoliths in eastern China, this study reported noble gas abundances and isotopic compositions of mantle-derived xenoliths from Kuandian of Liaoning Province, Huinan of Jilin Province and Hannuoba of Hebei Province. Compared with the middle ocean ridge basalt (MORB) and other continental areas, mantle-derived xenoliths in NE China are characterized by slightly low noble gas abundances, 3He/4He equivalent to or lower than that of MORB, 40Ar/36Ar lower than that of MORB, 38Ar/36Ar and Ne-Kr-Xe isotopic ratios equivalent to those of atmosphere. These results indicate the heterogeneity of subcontinental lithospheric mantle beneath northeastern China, that is, a MORB reservoir-like mantle beneath Kuandian and an enriched/metasomatized mantle beneath Huinan. Low 40Ar/ 36Ar ratios in the three studied areas may imply that a subducted atmospheric component has been preserved in the subcontinental lithospheric mantle.
文摘This paper deals with the chemical and isotopic compositions of escaped gases from the Rehai geothermal area in Tengchong county of Yunnan Province. Results indicate that there is the mantle-derived magmatic intrusion in shallow crust at this area. Modern mantle-derived mag-matic volatiles are being released currently in a steady stream by way of active faults. The escaped gases are mostly composed of CO2, together with subordinate amounts of H2S, N2, H2, CH4, SO2, CO and He. At the studied area, the north-south directed fault is the deepest, and it may be interlinked with the deep-seated thermal reservoir that would be directly recharged by the mantle-derived magmatic volatile. The He, C isotopic evidence reveals that the modern active magma beneath Rehai area may originate from the historical mantle-derived magma which caused the latest eruptive activity of volcanoes in that region.
基金This work was financially funded by the Chinese Academy of Sciences (Grant. No. KZCX1-07) the Ministry of Science and Technology of China (Grant No. 1999043210)partly by the National Natural Science Foundation of China (Grant. No. 49873022).
文摘This paper presents systematic studies on the C-O and Sr-Nd isotopic compositions for Cretaceous Badou carbonatites, Fangcheng basalts, and Jiaodong lamprophyres and Paleozoic Mengyin kimberlites in Shandong Province, China. Paleozoic kimberlites have normal and uniform C-O isotopic compositions with δ13C and δ18O in the range of -4.8‰--7.6‰ and +9.9‰-+13.2‰, respectively. However, Cretaceous three different types of mantle-derived rocks have quite different C-O isotopic compositions, indicating that the mantle sources are probably partially contaminated with organic carbon-bearing crustal materials. These Cretaceous rocks show uniform and EMII-like Sr-Nd isotopic compositions and also indicate that the mantle sources were affected by recycled crustal materials. Comparative studies of C-O and Sr-Nd isotopes reveal that the lithospheric mantle beneath the eastern North China Craton had different isotope characteristics in the Paleozoic, the early Cretaceous, and the Tertiary time. This demonstrates that the lithospheric mantle beneath the region underwent at least twice reconstructions since the Paleozoic. Available data imply that the first reconstruction mainly happened during the Triassic-Jurassic time with gradual changes and the second in the Cretaceous with abrupt changes. Results also show that the early Cretaceous (especially at 120-130 Ma) was perhaps the key period leading to the dramatic change of the Mesozoic geodynamics on the eastern North China Craton.
文摘Commercial accumulation of mantle-derived helium in the sedimentary shell is discussed. Generally speaking, a commercial helium pool is formed by accumulated 4He that comes from uranium and thorium via a-decay; therefore, it has a very low He/4He value in the magnitude of 10 . The helium concentration in some gas wells of eastern China oil/gas provinces is about or over 0.05%-0.1%, consequently forming commercial helium wells (pools), such as the Wangjinta Gas Pool in Songliao Basin, Huangqiao Gas Pool in North Jiangsu Basin and some gas wells in Sanshui Basin. Studies have proved that when the 3He/4He value of a helium gas pool is about 3.7×10 -6 -7.2× 10-6, namely mantle-derived helium in its total helium concentration accounts for 33. 5%-65.4%, it is a crust-mantle dual-source or dominantly mantle-derived helium gas pool, which is a novel helium resource and its formation is mainly related to the distribution of megafractures.
基金supported by the China National Key Basic Research and Development Program"973" (No.2009CB219506)
文摘Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of a mantle component throughout the island, which has been highly diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium is high in the northern island （12%-16% of total He） and gradually decreases towards southern coast （1%-3% of total He）. Such a distribution pattern is most likely controlled by the Pleocene-Quaternary volcanic activities in the northern island and groundwater circulation along the deep major faults. The 4~Ar/36Ar and N2/Ar ratios suggest that N2 and Ar of the hot spring gases are mostly meteoric. Although 13C values of CO2 （-20%0 to -27%0） with low concentrations are consistent with the biogenic origin, the combination of SHe/4He and 51SCco2 suggests a two end-member mixing of mantle and crustal components with CO2/3He ratios of 2x 109 and 8 1011, respectively. However, the low CO2/3He ratios （1- 22106） can not be ascribed in terms of the simple mixing but has to be explained by the addition of radiogenic 4He and loss of CO2 by calcite precipitation in the hydrothermal system, which is most likely controlled by the degree of gas-water-rock interaction.
文摘The 187Os/ 188Os ratios of spinel lherzolite xenoliths from Panshishan determined with N-TIMS are lower than that of the primitive mantle, which shows depleted mantle characteristics. Their positive correlation with Al-2O-3/MgO suggests that the geochemical behavior of trace elements Re and Os is similar to that of Al-2O-3 and MgO respectively during the magmatic evolution and Re-Os isotopic system is largely immune to mantle metasomatism. A model age of 2 8-3 4 Ga obtained by 187Os/ 188Os-Al-2O-3/MgO correlation might represent the homogeneous age of the mantle lithosphere beneath the area.
基金Project supported by the National Natural Science Foundation of China
文摘On the basis of the chemical components and stable isotopic compositions of escaped gases from the Tianchi volcanic geothermal area, the material sources of these gases are discussed, presenting that they are mainly derived from the residual mantle-derived magma in the crust; Changbai geothermal area may be directly interlinked with the eruption canal in history; there is a stable reservoir of the geothermal water and the deep-seated gases under the Changbai geothermal area, with water temperature of the reservoir being about (166±9)℃.
基金supported by the National Natural Science Foundation of China(Grant No.49972081)the Natural Science Foundation of Gansu Province of China(Grant No.3ZS041-A25-010).
文摘Fluids and noble gases of mantle-derived materials are important tracers forthe mantle information. Compositions of primary fluids and noble gases in mantle-derived mineralsfrom the Yishu area, Shandong Province, China, were tested by the methods of heat-bursting andheat-melting respectively. The fluids are mainly composed of CO_2, CO and H_2, which account forabout 90% of the total, and are similar to the mantle-derived rocks from other areas of easternChina; ratios of ~3He/~4He in almost all samples range from 0.82 Ra to 2.74 Ra, whereas^(40)Ar/^(36)Ar from 299.5 to 758.8. Both ranges are much lower than those of the typical oceanmantle-derived samples (such as MORB) and primarily reflect the influences of the atmosphericcomponents and the radiogenic isotopes. Ratios of C/~3He range from 27.6 x 10~9 to 1050 x 10~9,N_2/Ar from 927 to 56612, and N_2/~3He from 2.5 x 10~9 to 27 x 10~9, similar to those in westernUnited States and New Zealand which belong to the tectonic plate collision regions. The ratios fallin the intersect of mantle-crust-atmosphere in the comprehensive tracer-charts, reflecting theinfluences of the atmosphere and the crusts with organic components. Our results suggest that thecomposition of the primary fluids and the isotopic ratios of the noble gases may either reflect theevolution process of mantle-derived rocks connected with the rise and eruption of magma, or theinfluence of the ancient subduction-plate on the continental mantle of this region.
文摘There are four deposit types related to a Permian mafic complex in northern Xinjiang, i.e., copper-nickel sulfide deposit, vanadic titanomagnetite deposit, magnetite （-cobalt） deposit and Cu-Ni- VTiFe composite deposit. The deposits are distributed spanning tectonic units with close and consecutive metallogenic ages. A transitional deposit type can occur among the end-member deposits. Trace elements of host rocks show that they can derive from similar source area. Hence, they constitute a particular metallogenic series related to a mafic-ultramafic complex that is also a symbol series of the post-collisional stage of the Central Asia Metallogenic Province （CAMP）. The metallogenic ages of the series are between 260 Ma and 300 Ma throughout the Permian. Unlike mineralization from a mantle plume, the metallogenic period of this series spans at least 40 Ma. Compared with related deposits of the Emeishan mantle plume, the North Xinjiang series has a similar ore-forming element assemblage but has preferably developed Cu-Ni sulfide deposits rather than vanadic titanomagnetite deposits. In concomitance with this series, North Xinjiang area has developed a set of syntectonic Au-Cu-Mo metallogenic series related to a felsic volcanic-intrusive complex, which might indicate that there is no direct relationship with mantle plume activity. From early to late, i.e., the sequence of copper-nickel sulfide to magnetite （-cobalt） to vanadic titanomagnetite deposit, the host rock series evolves from mafic-ultramafic and tholeiite series to mafic and alkalic series, the ~REE content tends to increase with increasing of REE fractionation, and some of the trace elements （particularly LIL） also show an increasing tendency. The above evolutionary regularity possibly reflects a course where the magma source deepens and thermal interface moves down, energy gradually exhausts, and neo-continental crust forming in the postcollision stage tends to stabilize.
基金the China Postdoctoral Science Foundation the Key Project (No.9502010)of the former Ministry of Geology and Mineral Resources+1 种基金 the National Key BasicResearch Project (No.G1999043211) the NationalScience Foundation of China Outstanding Youth Grant(No.49925306).
文摘Taking the Himalayan granitoids around Kunjirap in the western Qinghai-Tibetplateau as an example, the authors present in this paper the characteristics of the granitoids richin mantle-derived fluid components and discuss their rock-forming mechanism. The research resultsindicate that the rock assemblage of the studied granitoids involves diopside syenite-diopsidegranite-biotite (monzonitic) granite, consisting mainly of K-feldspar, oligoclase, quartz,iron-phlogolite, diopside and edenite. The rocks are rich in mantle-derived fluid components ofvolatiles including F, alkali metal elements such as K, Na, Rb, Sr and Ha, and radiogenicheat-producing elements such as U and Th. They were generated by the influx of mantle-derived fluidsinto the lower crest to give rise to partial melting during the lithosphere thinning in theQinghai-Tibet plateau.
基金funded by Demonstration of ThreeDimensional Prospecting Evaluation for Deep Mineral Resources (Grant No. 2017YFC0601506)
文摘The Sanshandao Au deposit is located in the famous Sanshandao metallogenic belt,Jiaodong area.To date,accumulative Au resources of 1000 t have been identified from the belt.Sanshandao is a world-class gold deposit with Au mineralization hosted in Early Cretaceous Guojialing-type granites.Thus,studies on the genesis and ore-forming element sources of the Sanshandao Au deposit are crucial.He and Ar isotopic analyses of fluid inclusions from pyrite(the carrier of Au)indicate that the fluid inclusions have 3 He/4 He=0.043–0.21 Ra with an average of 0.096 Ra and 40 Ar/36 Ar=488–664 with an average of 570.8.These values represent the initial He and Ar isotopic compositions of ore-forming fluids for trapped fluid inclusions.The comparison of H–O isotopic characteristics combined with deposit geology and wall rock alteration reveals that the ore-forming fluids of the Sanshandao Au deposit show mixed crust–mantle origin characteristics,and they mainly comprise crust-derived fluid mixed with minor mantle-derived fluid and meteoric water during the uprising process.The ore-forming elements were generally sourced from pre-Cambrian meta-basement rocks formed by Mesozoic reactivation and mixed with minor shallow crustal and mantle components.
基金supported by the National Key Research and Development Program(Grant Nos.2016YFC0600103 and 2016YFC0600109)the National Natural Science Foundation of China(Grant No.41702042)。
文摘Lode gold deposits are among the most economically important types of gold deposits in the world.Globally,they formed mainly in three time intervals,2.8 to 2.5 Ga,2.1 to 1.8 Ga,and 700 Ma to the present.Sources of ore-forming fluids and other components are of critical importance in a better understanding of the genesis and the geodynamic controls of these deposits.Although ore-forming fluids were mostly derived from devolatization of sedimentary and/or volcanic sequences during greenschist to amphibolite facies metamorphism associated with orogenic deformation,magmatic hydrothermal fluids have been increasingly shown to be important in many gold deposits in various regions.In this review paper,we summarize the major features of lode gold deposits,possible sources of ore-forming fluids,and mechanisms of gold mineralization.While we acknowledge the critical role of metamorphically derived fluids in the genesis of such deposits worldwide,we emphasize that mantle-or basaltic magma-derived fluids may have been much more important than commonly thought.We use the Liaodong peninsula of the North China Craton as an example to demonstrate the significance of mantle-derived fluids.Integrating earlier studies and new data,we show that some of the late Mesozoic lode gold deposits in the North China Craton may have formed from magmatic hydrothermal fluids due to the extension and partial melting of the hydrated,metasomatized subcontinental lithosphere mantle,as best exemplified by the Wulong gold deposit.
基金supported by the National Natural Science Foundation of China grant 49972034the National 973 Project of China grant G1999043211
文摘We have analyzed the gold content of 65 samples of mantle-derived xenoliths and their host rocks from eastern China, which is found to be inhomogeneous, falling in the ranges of 1.0×109-8.2×109 (averaging 3.8 ×10-9) and 0.2×10-9-5.3×10-9 (averaging 2.7×10-9) in the mantle-derived xenoliths and the host basalts respectively. Except the samples from Wanquan County of Hebei Province and Anding County of Hainan Province, the gold content is the highest on the margins of the North China platform and decreases spatially towards the north and south, and temporally the samples of the Tertiary have a higher gold content than those of the Quaternary. The gold content of the mantle-derived xenoliths and the host Paleozoic kimberlites is 3.8×10-9-180×109and 0.1×10-9-38.0×10-9 respectively, which are higher than that in the mantle-derived xenoliths in basalt and the host Cenozoic basalts. The mantle-derived xenoliths have a higher gold content than the host rocks, but their relativity is not very clear, suggesting that the genetic relationship between them is complex. Our data indicate that the average gold content of the lithospheric mantle in eastern China is approximately equal to or approaching 3.8×10-9, which is lower than the average abundance of the upper mantle (5.0×10-9), higher than the average abundance of the continental crust (3.0×10-9) and only slightly higher than the average abundance of the lower continental crust (3.4×10-9). Except the samples from Hainan Province, the mantle-derived xenoliths in basalts with a high gold content are distributed on the two margins of the North China platform, corresponding to the gold deposits-concentrated districts in northwest Hebei Province and Shandong Province, showing the control by the old continental lithospheric mantle and the lower continental crust on the margins of the North China platform. The gold content of the mantle-derived xenoliths from Hainan Province ranges from 7.1×10-9 to 15×10-9, suggesting that some blocks of the lithospheric mantle in
基金the National Natural Science Foundation of China (Grant Nos. 40172053 , 49972051) the Important Direction Project of Knowledge Innovation in Resource and Environment Fields of the Chinese Academy of Sciences (Grant No. KZCX3-SW-128) the 2002 Foundation of State Key Laboratory of Gas Geochemistry.
文摘The values of the helium isotopes in the inclusions of the Ordovician reservoir rocks in the Kongxi buried hill belt in the Huanghua depression were first measured and the source of helium and its geological significance were investigated in comparison with those of the helium isotopes in the conclusions in the Ordovician rocks in the Ordos basin and the Tarim basin. The input of the mantle-derived helium into the inclusions in the carbonate reservoir rocks was found from the Konggu 3 well, the Konggu 4 well, and the Konggu 7 well in the Kongxi buried hill belt. The 3He/4He and R/Ra in the conclusions in the Ordovician oil-bearing reservoir rocks in the Konggu 7 well average 2.54×10-6(3) (sample quantity, the same below) and 1.82(3), respectively. The percent of the mantle-derived helium in the inclusions of the reservoir rocks in the Konggu 7 well reaches up to an average of 23.0%(3). The age of the contribution of the mantle-derived helium to the inclusions in the Kongxi buried hill belt is in the Late Triassic or the Early Tertiary. The finding of the mantle-derived helium shows that the interaction of the deep crust with mantle and the activity of deep faults occurred, the terrestrial heat flow value was high, and mantle-derived inorganic gas pools might be formed in the Kongxi buried hill belt. The finding of the mantle-derived helium in the inclusions of oil-bearing reservoir rocks also provides a new way for researching the activity of mantle-derived matter and its associated geological problems.
文摘Based on summarizing of the effect of mantle-derived fluid on the formation of ores, especially on gold ore, and with the latest investigations, such as the formation of ore from the action of shallow-deep fluid, the transportation effect of the thermal energy by mantle-derived fluid, this paper mainly aims at the effect of mantle-derived fluid on the generation of hydrocarbons. With the proof from geochemistry and fluid inclusion, it was suggested that the mantle-derived fluid not only supplied source materials for hydrocarbons, but also supplied essential energy and matter necessary for the generation of hydrocarbons. The mantle-derived fluid had a good effect, but at the same time it had an adverse effect under specific conditions, on the formation of reservoirs. This paper also discusses the future direction and significance of studying mantle-derived fluid.
基金This study was supported mainly by China National Natural Science Foundation Grant No.4880126partly by U.S. National Science Foundation Grant INT-8612713
文摘This paper deals with deformation textures and fabrics of mantle-derived xenoliths and dislocation microstructures of olivine in the upper mantle in the Penghu Islands, Taiwan. According to the calculation of the chemical composition of xenolith minerals (pyroxene), the equilibrium temperatures and pressures were 986-1116@ and 1.50-2.60 GPa, respectively. Deformation events in the upper mantle may fall into three sequences' (1) uniform steady-state flow deformation with high temperatures and low stresses, (2) shear flow deformation with high temperatures and relatively high stresses on diapiric margins of the upper mantle, and (3) extraction deformation of {110} glide bands with low temperatures and high strain rates. Deformation events and thermal structure of the upper mantle in the study area show that eastern Fujian and the Penghu Islands are characterized by very similar rheological properties of the upper mantle. Volcanism of basalts in the Penghu Islands is related to hot spots of the upper mantle under neath the Taiwan Strait, and diapirism and upwelling of the upper mantle are the dominant factors responsible for rifting of the continental margins in eastern China.
