2021 Vol. 54 No. 2
Abstract：
This paper presents an analysis of LA-ICP-MS zircon U-Pb dating, major elements and trace elements of Tianba diabase in Sanchazi area of Mianlue tectonic belt,south Qinling. It discusses the tectonic evolution of the Mianlue tectonic belt in Neoproterozoic.The LA-ICP-MS zircon U-Pb dating is (805.9±2.6) Ma(MSWD=0.033,n=9), indicative of a middle Neoproterozoic formation age.The geochemical data show that the Tianba diabase belongs to the calc-alkaline series.The REE pattern shows enrichment of LREE; The REE patterns show rightward incline.Eu negative anomaly is not obvious(the average δEu is 0.91).The trace elements pattern shows enrichment in LILEs(Rb, Ba, Sr,etc), and LREEs, and depletion of HFSEs (Nb, Ta),relatively depletion of P and Ti.Comprehensive study indicates that Tianba diabase has the geochemical characteristics of continental marginal magmatic rocks,which was formed by partial melting of the subduction fluid metasomatised enriched lithospheric mantle in an extensional setting. Mianlue tectonic zone and its adjacent areas was from regional convergent environment to postcollision-cracking environment in the middle Neoproterozoic (about 800 Ma).
This paper presents an analysis of LA-ICP-MS zircon U-Pb dating, major elements and trace elements of Tianba diabase in Sanchazi area of Mianlue tectonic belt,south Qinling. It discusses the tectonic evolution of the Mianlue tectonic belt in Neoproterozoic.The LA-ICP-MS zircon U-Pb dating is (805.9±2.6) Ma(MSWD=0.033,n=9), indicative of a middle Neoproterozoic formation age.The geochemical data show that the Tianba diabase belongs to the calc-alkaline series.The REE pattern shows enrichment of LREE; The REE patterns show rightward incline.Eu negative anomaly is not obvious(the average δEu is 0.91).The trace elements pattern shows enrichment in LILEs(Rb, Ba, Sr,etc), and LREEs, and depletion of HFSEs (Nb, Ta),relatively depletion of P and Ti.Comprehensive study indicates that Tianba diabase has the geochemical characteristics of continental marginal magmatic rocks,which was formed by partial melting of the subduction fluid metasomatised enriched lithospheric mantle in an extensional setting. Mianlue tectonic zone and its adjacent areas was from regional convergent environment to postcollision-cracking environment in the middle Neoproterozoic (about 800 Ma).
Abstract：
Hualong rock group is the basement rock of Nanshan tectonic belt in Qinghai province.Its formation age remains controversial.This paperstudied the gneissic granodiorite, which intruded into Hualong rock group, through petrology, chronology and petrogeochemistry.The research shows that the rock has high SiO2 and Al2O3, and low K,P,Ti.The content of SiO2 is 69.48%, of K2O, 2.35%, of K2O/Na2O, 0.59,of (Na2O+K2O), 6.27%, of MgO, 1.32%, of Al2O3, 13.68%, belonging to mid-K calc-alkaline and prealuminous series.The content of rare earth elements is lower,∑REE being 253.77×10-6.The rock is enriched in LREE and depeleted in HREE.The REE patterns show rightward incline and moderate negative Eu anomaly.Compared with the adjacent elements,the trace elements show enrichment of LILE(Th,U,Ba),evident depletion of K,P,Ti, and relative depletion of Rb,Sr.Zr and Hf were positive anomaly.The rock has the characteristics of A-typegranite with the forming age of(701±63) Ma.Combined with the geochemical characteristics and regional magmatic activity events, it is held that the gneissic granodiorite was generated in an extensional environment, being the magmatic activity of the Rodinia supercontinent cracking event in Qilian block.
Hualong rock group is the basement rock of Nanshan tectonic belt in Qinghai province.Its formation age remains controversial.This paperstudied the gneissic granodiorite, which intruded into Hualong rock group, through petrology, chronology and petrogeochemistry.The research shows that the rock has high SiO2 and Al2O3, and low K,P,Ti.The content of SiO2 is 69.48%, of K2O, 2.35%, of K2O/Na2O, 0.59,of (Na2O+K2O), 6.27%, of MgO, 1.32%, of Al2O3, 13.68%, belonging to mid-K calc-alkaline and prealuminous series.The content of rare earth elements is lower,∑REE being 253.77×10-6.The rock is enriched in LREE and depeleted in HREE.The REE patterns show rightward incline and moderate negative Eu anomaly.Compared with the adjacent elements,the trace elements show enrichment of LILE(Th,U,Ba),evident depletion of K,P,Ti, and relative depletion of Rb,Sr.Zr and Hf were positive anomaly.The rock has the characteristics of A-typegranite with the forming age of(701±63) Ma.Combined with the geochemical characteristics and regional magmatic activity events, it is held that the gneissic granodiorite was generated in an extensional environment, being the magmatic activity of the Rodinia supercontinent cracking event in Qilian block.
Abstract：
Huangyakou lead-zinc deposit is located outside Baiyin orefield,being the main prospecting mining areas. Its metallogenic characteristics have long been considered to be similar to that of Xiaotieshan lead-zinc deposit. Through the LA-ICP-MS zircon U-Pb isotope dating of the meta-acid volcanic rocks in Huangyakou lead-zinc deposit,the age of meta-rhyolite is(507.6±1.8) Ma (MSWD=0.23, Points=23), belonging to the Middle Cambrian.This is also the formation age of Huangyakou lead-zinc deposit.On the basis of previous research,it is held that Baiyin copper polymetallic ore is formed in (467.1±2.2)-(465.0±3.7) Ma which belongs to the Middle Ordovician.There for,Huangyakou lead-zinc deposit was formed earlier than Baiyin copper polymetallic ore.It is proposed that Baiyin copper polymetallic orefield and its periphery are multi-stage metallogenic, which has some implications in the prospecting of the Baiyin orefield.
Huangyakou lead-zinc deposit is located outside Baiyin orefield,being the main prospecting mining areas. Its metallogenic characteristics have long been considered to be similar to that of Xiaotieshan lead-zinc deposit. Through the LA-ICP-MS zircon U-Pb isotope dating of the meta-acid volcanic rocks in Huangyakou lead-zinc deposit,the age of meta-rhyolite is(507.6±1.8) Ma (MSWD=0.23, Points=23), belonging to the Middle Cambrian.This is also the formation age of Huangyakou lead-zinc deposit.On the basis of previous research,it is held that Baiyin copper polymetallic ore is formed in (467.1±2.2)-(465.0±3.7) Ma which belongs to the Middle Ordovician.There for,Huangyakou lead-zinc deposit was formed earlier than Baiyin copper polymetallic ore.It is proposed that Baiyin copper polymetallic orefield and its periphery are multi-stage metallogenic, which has some implications in the prospecting of the Baiyin orefield.
Abstract：
Lawumedium skarn type Zn-Cu polymetallic deposit is located in the eastern section of the Middle Gangdise Pb-Zn polymetallic metallogenic belt.The deposit is dominated by Cu-Pb-Zn mineralization, accompanied by W-Sn mineralization,obviously different from the Pb-Zn-Ag deposits developed in the same region.The Zn-Cu polymetallic ore bodies are mainly produced in the skarn of the contact zone between the monzogranite and carboniferous system, and occur in the hornfels sandy slate.To find out the source of ore-forming materials, the authors carried out the in-situ S isotope analysis by LA-MC-ICP-MS.The results are as follows:in Lawu deposit, the δ34Sv-CDT values in pyrite is-2.57‰~-1.17‰, averaging-1.65‰; theδ34Sv-CDT values in chalcopyrite is+1.32‰~+2.74‰, averaging+1.73‰; theδ34Sv-CDT values in galena is+0.84‰~+1.53‰,with an average value of+1.09‰. The in-situ S isotope distribution is relatively concentrated, the δ34Sv-CDT is-2.57‰~+2.74‰,averaging +0.09‰. Comprehensive analysis shows that the composition of isotopic sulfide in Lawu Zn-Cu polymetallic ore deposit is similar to that of the lead-zinc polymetallic deposit extensively developed in this area,relating to S-type granite caused by the orogenic collision of Indiacontinent and Eurasia.Ore-forming material was a typical skarn type deposit,rather than the sedimentary exhalative deposit previous studies suggested.
Lawumedium skarn type Zn-Cu polymetallic deposit is located in the eastern section of the Middle Gangdise Pb-Zn polymetallic metallogenic belt.The deposit is dominated by Cu-Pb-Zn mineralization, accompanied by W-Sn mineralization,obviously different from the Pb-Zn-Ag deposits developed in the same region.The Zn-Cu polymetallic ore bodies are mainly produced in the skarn of the contact zone between the monzogranite and carboniferous system, and occur in the hornfels sandy slate.To find out the source of ore-forming materials, the authors carried out the in-situ S isotope analysis by LA-MC-ICP-MS.The results are as follows:in Lawu deposit, the δ34Sv-CDT values in pyrite is-2.57‰~-1.17‰, averaging-1.65‰; theδ34Sv-CDT values in chalcopyrite is+1.32‰~+2.74‰, averaging+1.73‰; theδ34Sv-CDT values in galena is+0.84‰~+1.53‰,with an average value of+1.09‰. The in-situ S isotope distribution is relatively concentrated, the δ34Sv-CDT is-2.57‰~+2.74‰,averaging +0.09‰. Comprehensive analysis shows that the composition of isotopic sulfide in Lawu Zn-Cu polymetallic ore deposit is similar to that of the lead-zinc polymetallic deposit extensively developed in this area,relating to S-type granite caused by the orogenic collision of Indiacontinent and Eurasia.Ore-forming material was a typical skarn type deposit,rather than the sedimentary exhalative deposit previous studies suggested.
Abstract：
Research on the Early Paleozoic geological bodies exposed in Nuratau, Uzbekistan, is key to reconstruct the tectonic setting and evolution process of the Turkestan Ocean in the western south Tianshan.This paper analyzed the source of sedimentary material and the tectonic attributeby source tracing of the Ordovician-Silurian clastic rocksin southern Nuratau.The results show that this suite of clastic rocks is mainly comprised of fine-grained greywacke which formed inoffshore beach setting of passive continental margin. The lithology is of acidic magmatic rocks and old sedimentary rocks.The peak age of the detrital zircons in fine-grained sandstone is nearly 800Ma,which corresponds to Rodinia supercontinent cracking event;the secondary peak ages are 530Ma and 440Ma, suggesting a large terrane assembly event in the Early Paleozoic. The authors have reached the conclusion that in Early Paleozoic the Turkestan Ocean spread in the east-west direction with the active continental margin to the north and the passive continental margin to the south.Sedimentary materials of the passive continental margin were from the Rodinia supercontinent cracking event and the Early Paleozoic tectonic event.
Research on the Early Paleozoic geological bodies exposed in Nuratau, Uzbekistan, is key to reconstruct the tectonic setting and evolution process of the Turkestan Ocean in the western south Tianshan.This paper analyzed the source of sedimentary material and the tectonic attributeby source tracing of the Ordovician-Silurian clastic rocksin southern Nuratau.The results show that this suite of clastic rocks is mainly comprised of fine-grained greywacke which formed inoffshore beach setting of passive continental margin. The lithology is of acidic magmatic rocks and old sedimentary rocks.The peak age of the detrital zircons in fine-grained sandstone is nearly 800Ma,which corresponds to Rodinia supercontinent cracking event;the secondary peak ages are 530Ma and 440Ma, suggesting a large terrane assembly event in the Early Paleozoic. The authors have reached the conclusion that in Early Paleozoic the Turkestan Ocean spread in the east-west direction with the active continental margin to the north and the passive continental margin to the south.Sedimentary materials of the passive continental margin were from the Rodinia supercontinent cracking event and the Early Paleozoic tectonic event.
Abstract：
In recent years, shale oil incontinental basins of China has become a hotspot in oil and gas exploration and development.This paper studied the lithofacies characteristics and sedimentary evolution model of the 7th member of Dameigou formation of Middle JurassicinYuqia area, north Qaidam Basin by means of observation of core and thin section, organic geochemistry and X-ray diffraction experiments.It provided theoretical basis for the development and distribution of high-quality source rocks.The results show that there are six types of lithofacies, which can be divided into three sedimentary stagesin the vertical direction.Stage A is the delta front and shallow lake sedimentary environment under warm and humid climate,which develops massive poor-organicclay and siliceous mudstone facies.Strong terrestrial input leads to the oxygen-rich water bodywith an average TOC of 0.79%.Therefore, shale oil and gas potential is poor at this stag.Stage B is a semi-deep to deep lake sedimentary environment under tectonic subsidence, which develops the massive rich organic clay mudstone facies.The deep-lakereducing environment provides good condition for the preservation of organic matter.A higher potential of oil and gas appears with an average TOC of 4.16%.Stage C is a semi-deep to deep lake sedimentary environment jointly controlled by arid climate and tectonic subsidence, which develops the laminar calcareous organic-rich matter,calcareous clay-rich and clayey mudstone facies.Good preservation conditions of organic matter by lake salinity stratification and high productivity of adaptive alga make stage C the highest shale oil and gas potential with an average TOC of 5.03%.
In recent years, shale oil incontinental basins of China has become a hotspot in oil and gas exploration and development.This paper studied the lithofacies characteristics and sedimentary evolution model of the 7th member of Dameigou formation of Middle JurassicinYuqia area, north Qaidam Basin by means of observation of core and thin section, organic geochemistry and X-ray diffraction experiments.It provided theoretical basis for the development and distribution of high-quality source rocks.The results show that there are six types of lithofacies, which can be divided into three sedimentary stagesin the vertical direction.Stage A is the delta front and shallow lake sedimentary environment under warm and humid climate,which develops massive poor-organicclay and siliceous mudstone facies.Strong terrestrial input leads to the oxygen-rich water bodywith an average TOC of 0.79%.Therefore, shale oil and gas potential is poor at this stag.Stage B is a semi-deep to deep lake sedimentary environment under tectonic subsidence, which develops the massive rich organic clay mudstone facies.The deep-lakereducing environment provides good condition for the preservation of organic matter.A higher potential of oil and gas appears with an average TOC of 4.16%.Stage C is a semi-deep to deep lake sedimentary environment jointly controlled by arid climate and tectonic subsidence, which develops the laminar calcareous organic-rich matter,calcareous clay-rich and clayey mudstone facies.Good preservation conditions of organic matter by lake salinity stratification and high productivity of adaptive alga make stage C the highest shale oil and gas potential with an average TOC of 5.03%.
Abstract：
On the basis of field observations of the Pliocene conglomerates of Hanjiagou in the northern margin of west Qinling, this paper carried out the research on the sedimentary characteristics and provenance.The results show that Hanjiagou conglomerate is mainly composed offine gravel.The components are mainly sandstone and limestone, others aregranite and quartzite.The poor roundness of gravels is the result of the combined action of lithology, hydrodynamic conditions and transportation distance.The proluvial conglomerates and alluvial conglomerates occured alternately.The grain size presents a reverse cycle, which reveals the progradational development of the fan. The flat surface indicates a south-to-north direction of paleocurrent.The provenance is 30-50km away in the south and southwest of the mountain areas. The sandstone gravels mainly come from Dacaotan group of Devonian System, east of Minxian county.Limestone gravels are mainly from the Permian Daguanshan formation.Granitegranodiorite gravels may come from Jiaochangba-Luchuba granodiorite monzogranite in south Zhangxian.The conglomerates is the product of the continuous northeastern extension of Pliocene Tibetan Plateau, transported by rivers from south to north in dry climate and deposited in the middle of the root of alluvial fan.
On the basis of field observations of the Pliocene conglomerates of Hanjiagou in the northern margin of west Qinling, this paper carried out the research on the sedimentary characteristics and provenance.The results show that Hanjiagou conglomerate is mainly composed offine gravel.The components are mainly sandstone and limestone, others aregranite and quartzite.The poor roundness of gravels is the result of the combined action of lithology, hydrodynamic conditions and transportation distance.The proluvial conglomerates and alluvial conglomerates occured alternately.The grain size presents a reverse cycle, which reveals the progradational development of the fan. The flat surface indicates a south-to-north direction of paleocurrent.The provenance is 30-50km away in the south and southwest of the mountain areas. The sandstone gravels mainly come from Dacaotan group of Devonian System, east of Minxian county.Limestone gravels are mainly from the Permian Daguanshan formation.Granitegranodiorite gravels may come from Jiaochangba-Luchuba granodiorite monzogranite in south Zhangxian.The conglomerates is the product of the continuous northeastern extension of Pliocene Tibetan Plateau, transported by rivers from south to north in dry climate and deposited in the middle of the root of alluvial fan.
Abstract：
The Triassic Jiucaiyuanzi Formation is one of the main hydrocarbon-bearing strata in Fudong slope area of Junggar basin.The lack of research on the types and characteristics of the diagenesis affected the recognition and development of the reservoirs.By using such testing technology as slice observation, SEM,property analysis, X-Ray and electron probe,the diagenesis characteristics and its effect on reservoir property were clarified.Results show that reservoir types of Jiucaiyuanzi formation are mainly middle pore and low permeability reservoirs,with some types being middle pore and middle-high permeability reservoirs. The reservoirs have strong micro anisotropy caused by diagenesis.It is concluded that the diagenesis of compaction,cementation and dissolution was developed in Jiucaiyuanzi formation.The diagenesis stage is in stage A.The moderatein tensity of the compaction is the key factors to poor property; the intensity of cementation is moderate-strong and the intensity of dissolution is weak-moderate, sometimes strong. Calcite, clay minerals and siliceous cementation further decreases the property of reservoirs, while zeolite cementation and its dissolution improves the property.
The Triassic Jiucaiyuanzi Formation is one of the main hydrocarbon-bearing strata in Fudong slope area of Junggar basin.The lack of research on the types and characteristics of the diagenesis affected the recognition and development of the reservoirs.By using such testing technology as slice observation, SEM,property analysis, X-Ray and electron probe,the diagenesis characteristics and its effect on reservoir property were clarified.Results show that reservoir types of Jiucaiyuanzi formation are mainly middle pore and low permeability reservoirs,with some types being middle pore and middle-high permeability reservoirs. The reservoirs have strong micro anisotropy caused by diagenesis.It is concluded that the diagenesis of compaction,cementation and dissolution was developed in Jiucaiyuanzi formation.The diagenesis stage is in stage A.The moderatein tensity of the compaction is the key factors to poor property; the intensity of cementation is moderate-strong and the intensity of dissolution is weak-moderate, sometimes strong. Calcite, clay minerals and siliceous cementation further decreases the property of reservoirs, while zeolite cementation and its dissolution improves the property.
Abstract：
Heilangou gold field is located in the northern part of Qixia-Penglai gold metallogenic belt of Jiaodong,Shandong province.There are many quartz vein type of gold deposits as Heilangou, Hexi, Hougezhuang and Chugezhuang,etc.The gold mineralization mainly occurs in quartz veins containing pyrite and polymetallic sulfide. Pyrite is the main gold bearing mineral,therefore the prospecting based on the typomorphic characteristics of pyrite thermoelectricity is of practical significance.The thermoelectric properties of 46 pyriteswere measured by a new in-situ mineral thermoelectric instrument. The results show that the P-type ratios of pyrite are mostly above 90%,being in the elevation range of -170~-616m, indicating that the ore bodies exposed are at the top of the deposit.The thermoelectric coefficient is especiallyconcentrated in the range of 200~350 μV·℃-1.The average value of the vertical extension index (30.4%) calculated by the thermoelectric coefficient indicates that the current exploration position is in the upper part of the deposit.It is held thatthere is still much metallogenic potential deep in Heilangou gold field.
Heilangou gold field is located in the northern part of Qixia-Penglai gold metallogenic belt of Jiaodong,Shandong province.There are many quartz vein type of gold deposits as Heilangou, Hexi, Hougezhuang and Chugezhuang,etc.The gold mineralization mainly occurs in quartz veins containing pyrite and polymetallic sulfide. Pyrite is the main gold bearing mineral,therefore the prospecting based on the typomorphic characteristics of pyrite thermoelectricity is of practical significance.The thermoelectric properties of 46 pyriteswere measured by a new in-situ mineral thermoelectric instrument. The results show that the P-type ratios of pyrite are mostly above 90%,being in the elevation range of -170~-616m, indicating that the ore bodies exposed are at the top of the deposit.The thermoelectric coefficient is especiallyconcentrated in the range of 200~350 μV·℃-1.The average value of the vertical extension index (30.4%) calculated by the thermoelectric coefficient indicates that the current exploration position is in the upper part of the deposit.It is held thatthere is still much metallogenic potential deep in Heilangou gold field.
Abstract：
Lithologic interpretation and alteration information extracting based on ASTER spectral analysis have been widely used in ore exploration.The authors carried out the study in Nianzha gold deposit of Yarlung Zangbo suture zone.Minerals components such as Fe3+, Fe2+, Al-OH, Mg-OH, silicate and carbonate were analyzed based on ASTER spectrum. This paper used "band radio method + false color synthesis" for lithologic classification and geological mapping and quantitatively delineated the range of mineralization-relatedalteration zone and two prospecting target areas with the "geologic-remote sensing profiles + best density seperation method". The results show that lithological mapping and alteration information extracting based on aster spectral are suitable for prospecting prediction in high altitude areas of Tibet, which can accurately indicate the key prospecting indicators of lithology and alteration.It proves to be an important means of rapid and effective ore exploration in Tibet, and provides reference for other deposits of the same type in the belt.
Lithologic interpretation and alteration information extracting based on ASTER spectral analysis have been widely used in ore exploration.The authors carried out the study in Nianzha gold deposit of Yarlung Zangbo suture zone.Minerals components such as Fe3+, Fe2+, Al-OH, Mg-OH, silicate and carbonate were analyzed based on ASTER spectrum. This paper used "band radio method + false color synthesis" for lithologic classification and geological mapping and quantitatively delineated the range of mineralization-relatedalteration zone and two prospecting target areas with the "geologic-remote sensing profiles + best density seperation method". The results show that lithological mapping and alteration information extracting based on aster spectral are suitable for prospecting prediction in high altitude areas of Tibet, which can accurately indicate the key prospecting indicators of lithology and alteration.It proves to be an important means of rapid and effective ore exploration in Tibet, and provides reference for other deposits of the same type in the belt.
Abstract：
Yangxie gold deposit is a medium-sized one located in the eastern section of the Yangxie-Fengbeihe Au-W metallogenic belt, East Qinling.The gold orebodies are mainly composed of gold-bearing quartz veins controlled by NE-NNE and NW-NNW trending faults and hosted in the Neoproterozoic Yangxie gneiss suite in Shangdan fault.Metal minerals in the ore are medium-low temperature mineral associations, and mainly consist of pyrite, native gold, chalcopyrite, tetrahedrite, sphalerite and galena.The process of the hydrothermal ore-forming can be divided into four metallogenic stages:thepotassium feldspar-quartz stage, the quartz-coarse grained pyrite-native gold stage, the quartz-fine grained pyrite-native gold-polymetallic sulfide stage and the carbonate stage.The proximal wall-rock alterations are characterized by potassic alteration, silification and pyritization, while the distal alterations are dominated by chloritization and carbonation. The Yangxie gold deposit is mainly controlled by the faults, the wall-rock and the Indosinian granite;its metallogenic age is no earlier than the Late Triassic.
Yangxie gold deposit is a medium-sized one located in the eastern section of the Yangxie-Fengbeihe Au-W metallogenic belt, East Qinling.The gold orebodies are mainly composed of gold-bearing quartz veins controlled by NE-NNE and NW-NNW trending faults and hosted in the Neoproterozoic Yangxie gneiss suite in Shangdan fault.Metal minerals in the ore are medium-low temperature mineral associations, and mainly consist of pyrite, native gold, chalcopyrite, tetrahedrite, sphalerite and galena.The process of the hydrothermal ore-forming can be divided into four metallogenic stages:thepotassium feldspar-quartz stage, the quartz-coarse grained pyrite-native gold stage, the quartz-fine grained pyrite-native gold-polymetallic sulfide stage and the carbonate stage.The proximal wall-rock alterations are characterized by potassic alteration, silification and pyritization, while the distal alterations are dominated by chloritization and carbonation. The Yangxie gold deposit is mainly controlled by the faults, the wall-rock and the Indosinian granite;its metallogenic age is no earlier than the Late Triassic.
Abstract：
This papers ystematically studied the distribution characteristics and ore-forming stages of gold orebody in Xiaoqinling area of Shaanxi Province through microthermometry and Laser Raman spectroscopy.The physicochemical characteristics and ore-forming model of Xiaoqinling gold deposit were analyzed.Based on the previous analysis,the authors hold that the compound antiform of Dayueping-Jinluoban is the main ore-controlling structural framework.The distribution of orebody is controlled by the secondary embrittlement ductile faults derived from the compound antiform.The main ore-bearing structure is along the east-west fault zoneparallel to the fold hinge.The ore-forming process is divided into four main stages.It is in the mineralization stage (phase Ⅲ) that formed gold-bearing polymetallic sulfide deposits.The ore-forming fluidis of low salinity and rich in CO2, with the metallogenic condition being medium temperature and medium pressure.The decrease of pressure by the expansion of mineralization space and the mixing of meteoric precipitation caused gold deposit precipitation.
This papers ystematically studied the distribution characteristics and ore-forming stages of gold orebody in Xiaoqinling area of Shaanxi Province through microthermometry and Laser Raman spectroscopy.The physicochemical characteristics and ore-forming model of Xiaoqinling gold deposit were analyzed.Based on the previous analysis,the authors hold that the compound antiform of Dayueping-Jinluoban is the main ore-controlling structural framework.The distribution of orebody is controlled by the secondary embrittlement ductile faults derived from the compound antiform.The main ore-bearing structure is along the east-west fault zoneparallel to the fold hinge.The ore-forming process is divided into four main stages.It is in the mineralization stage (phase Ⅲ) that formed gold-bearing polymetallic sulfide deposits.The ore-forming fluidis of low salinity and rich in CO2, with the metallogenic condition being medium temperature and medium pressure.The decrease of pressure by the expansion of mineralization space and the mixing of meteoric precipitation caused gold deposit precipitation.
Abstract：
Hongshiquan deposit in Chinais the most typical uranium deposit of pegmatite type.In recent years,Hongshiquan deposit is found to have multi-stage uranium mineralization. Different ore,uranium minerals and alteration characteristics formed in different mineralization periods.Studies of different uranium mineralization show that in the late Zhongtiao period,granitic magma evolved into the light flesh red pegmatite granite ore rich in uraninite, with the ore concentrated in the core of the pegmatite granite, basically without alteration.In the Hercynian ore bearing hydrothermal solution, sodium metasomatic mineralization occurred along the contact fracture zone between the pegmatite granite and biotiteplagioschist,forming purple red pegmatite granite ore and asphalt uranium mineral.The ore develops albitization,hematite mineralization, carbonation, chloritization and other alteration.Therefore, the core of pegmatite granite and the contact fracture zone between pegmatite granite and schist are the important prospecting areas.
Hongshiquan deposit in Chinais the most typical uranium deposit of pegmatite type.In recent years,Hongshiquan deposit is found to have multi-stage uranium mineralization. Different ore,uranium minerals and alteration characteristics formed in different mineralization periods.Studies of different uranium mineralization show that in the late Zhongtiao period,granitic magma evolved into the light flesh red pegmatite granite ore rich in uraninite, with the ore concentrated in the core of the pegmatite granite, basically without alteration.In the Hercynian ore bearing hydrothermal solution, sodium metasomatic mineralization occurred along the contact fracture zone between the pegmatite granite and biotiteplagioschist,forming purple red pegmatite granite ore and asphalt uranium mineral.The ore develops albitization,hematite mineralization, carbonation, chloritization and other alteration.Therefore, the core of pegmatite granite and the contact fracture zone between pegmatite granite and schist are the important prospecting areas.
Abstract：
large-scale stable host sandbodies were discovered in the central Bei'er depression of Hailar Basin。The sandstone belonged to the longitudinal braided fluvial facies of the upper Yimin Formation in Low Cretaceous.It was at 200~500 m deep, and the whole thickness ranged from 50 m to 150m with a single being 5m. The lithology was composed mainly of glutenite and mediumcoarse sands followed of fine sandstone.The sandstone shows loose structure,excellent permeability, high debris content and low maturity of composition and structure.The ZTR index of 25%~52% and the unstable heavy minerals indicated that the sandstone deposit was adjacent to the provenance area.The clay minerals were characterized by abund antmont morillonite and little kaolinite.Rare content of carbon chips and pyrite indicated the alkaline groundwater condition.The average values of uranium, organic carbon, total sulfur and △Eh in primary sandstone were 4.91×10-6, 0.08%, 0.03% and 16.25m vres pectively,suggesting that the reduction capacity of the internal uranium was low.Uranium mineralization mainly occurred in the gray sand bodies in both sides of the interlayer oxidation zone, with an average uranium content of 0.03~0.38kg/m2and the characteristics of low thickness,low grade and small scale.Through comprehensive analysis it is held that the host sandbody has a favorable metallogenic potential in interlayer oxidation uranium deposit.
large-scale stable host sandbodies were discovered in the central Bei'er depression of Hailar Basin。The sandstone belonged to the longitudinal braided fluvial facies of the upper Yimin Formation in Low Cretaceous.It was at 200~500 m deep, and the whole thickness ranged from 50 m to 150m with a single being 5m. The lithology was composed mainly of glutenite and mediumcoarse sands followed of fine sandstone.The sandstone shows loose structure,excellent permeability, high debris content and low maturity of composition and structure.The ZTR index of 25%~52% and the unstable heavy minerals indicated that the sandstone deposit was adjacent to the provenance area.The clay minerals were characterized by abund antmont morillonite and little kaolinite.Rare content of carbon chips and pyrite indicated the alkaline groundwater condition.The average values of uranium, organic carbon, total sulfur and △Eh in primary sandstone were 4.91×10-6, 0.08%, 0.03% and 16.25m vres pectively,suggesting that the reduction capacity of the internal uranium was low.Uranium mineralization mainly occurred in the gray sand bodies in both sides of the interlayer oxidation zone, with an average uranium content of 0.03~0.38kg/m2and the characteristics of low thickness,low grade and small scale.Through comprehensive analysis it is held that the host sandbody has a favorable metallogenic potential in interlayer oxidation uranium deposit.
Abstract：
In the Changjing section of Yingdong Oilfield, Qaidam Basin,the heterogeneity in interlayers and the uncertain production capacity caused many problems under the circumstances of low price.The authors use seepage coefficient, storage coefficient and oil saturation as the fisher discriminant function to quantitatively evaluatethe reservoir productivity.The conformity rate of the theoretical model is above 80%,compared to the actual production data and the theoretical functions, meeting the need of reservoir development.The research providesa basis for the comprehensive use of monolayer sand body, the deployment of the production capacity and the prediction and utilization of the reservoir.
In the Changjing section of Yingdong Oilfield, Qaidam Basin,the heterogeneity in interlayers and the uncertain production capacity caused many problems under the circumstances of low price.The authors use seepage coefficient, storage coefficient and oil saturation as the fisher discriminant function to quantitatively evaluatethe reservoir productivity.The conformity rate of the theoretical model is above 80%,compared to the actual production data and the theoretical functions, meeting the need of reservoir development.The research providesa basis for the comprehensive use of monolayer sand body, the deployment of the production capacity and the prediction and utilization of the reservoir.
Abstract：
Based on the seismic data, logging, core analysis and testing, this paper discusses the reservoir forming characteristics,the main controlling factors and favorable exploration direction of the tight oil in carbonate conglomerate.The results show that the conglomerate in the lower 3rd member of Shulu saghas mixed terrigenous and endogenous characteristics.Marl source rocks,interbedded with conglomerate,with large thickness, wide distribution and high organic matter abundance, provide a material basis for the formation of tight conglomerate oil reservoirs.The faults have some effects on the formation of tight conglomerate oil reservoirs.In conclusion, high-quality source rocks,degree of the reservoir developmentand favorable reverse fault traps are the main controlling factors for tight conglomerate oil accumulation.The accumulation mode is "source-reservoir symbiosis".It is suggested that the future exploration should be near the marlite hydrocarbon-generating center and far from the fault development zone,being in the gravel body of slump fan origin near the slope break zone.
Based on the seismic data, logging, core analysis and testing, this paper discusses the reservoir forming characteristics,the main controlling factors and favorable exploration direction of the tight oil in carbonate conglomerate.The results show that the conglomerate in the lower 3rd member of Shulu saghas mixed terrigenous and endogenous characteristics.Marl source rocks,interbedded with conglomerate,with large thickness, wide distribution and high organic matter abundance, provide a material basis for the formation of tight conglomerate oil reservoirs.The faults have some effects on the formation of tight conglomerate oil reservoirs.In conclusion, high-quality source rocks,degree of the reservoir developmentand favorable reverse fault traps are the main controlling factors for tight conglomerate oil accumulation.The accumulation mode is "source-reservoir symbiosis".It is suggested that the future exploration should be near the marlite hydrocarbon-generating center and far from the fault development zone,being in the gravel body of slump fan origin near the slope break zone.
Abstract：
The automatic data acquisition system identifies, collects and processes production data automatically in different formats, structures and categories, which helps improvethe data acquisition efficiency of coalbed methane production.The system search table title and analyze table structure of Word file and Excel file, and use table recognition or keyword recognition to identify single cell, continuous multiple cells, key value pairs and data table.Results from coalbed methane wells of south Shizhuang block show that the system can extract and collect production data accurately and efficiently,providing an effective technical approach for the coalbed methane fields.
The automatic data acquisition system identifies, collects and processes production data automatically in different formats, structures and categories, which helps improvethe data acquisition efficiency of coalbed methane production.The system search table title and analyze table structure of Word file and Excel file, and use table recognition or keyword recognition to identify single cell, continuous multiple cells, key value pairs and data table.Results from coalbed methane wells of south Shizhuang block show that the system can extract and collect production data accurately and efficiently,providing an effective technical approach for the coalbed methane fields.
Abstract：
Based on the"pre-survey of Juhugeng coal mine in Tianjun County, Qinghai Province" and the simulation research on the distribution characteristics and hydrocarbon-generating process of the source rocks, it is considered that there are three kinds of source rocks:coal, dark mudstone and oil shale.The coal seams are mainly distributed in the upper section of Muli formation; dark mudstone is in the upper section of Muli formation and Jiangcang formation;oil shale is mainly distributed in the upper section of Jiangcang formation. Two hydrocarbon-generating processes of the source rocks are late Jurassic-early Cretaceous andearly Paleogene with the former being the mainhydrocarbon-generating stage.
Based on the"pre-survey of Juhugeng coal mine in Tianjun County, Qinghai Province" and the simulation research on the distribution characteristics and hydrocarbon-generating process of the source rocks, it is considered that there are three kinds of source rocks:coal, dark mudstone and oil shale.The coal seams are mainly distributed in the upper section of Muli formation; dark mudstone is in the upper section of Muli formation and Jiangcang formation;oil shale is mainly distributed in the upper section of Jiangcang formation. Two hydrocarbon-generating processes of the source rocks are late Jurassic-early Cretaceous andearly Paleogene with the former being the mainhydrocarbon-generating stage.
Abstract：
Chang 3 member is the main oil producing layerin Yanchang formation of Xunyi Block.On the basis of the previous research,this paper analyzes the development characteristics of the surplus pressure and the relationship between surplus pressure and hydrocarbon accumulationusing the principles of reservoir forming dynamics and pressure seal box, combined with the core test and the analysis data.The results show that:vertically, the pressure structure decides the development horizon of the reservoir, i.e. Chang 7 reservoir accumulates oil and gas in the pressure storage tank under a sudden pressure structure; Chang 3 and Chang 6 reservoir accumulates in the upper gradual change zone under a gradual changing pressure structure.Horizontally,the surplus pressure controls the plane distribution of oil and gas reservoirs.Both Chang 6 and Chang 7 reservoirs are located in the area with high residual pressure and sufficient charging power, which is conducive to hydrocarbon accumulation. The research is of guiding significance for the future exploration and deployment of tight oil in Yanchang formation of Xunyi block.
Chang 3 member is the main oil producing layerin Yanchang formation of Xunyi Block.On the basis of the previous research,this paper analyzes the development characteristics of the surplus pressure and the relationship between surplus pressure and hydrocarbon accumulationusing the principles of reservoir forming dynamics and pressure seal box, combined with the core test and the analysis data.The results show that:vertically, the pressure structure decides the development horizon of the reservoir, i.e. Chang 7 reservoir accumulates oil and gas in the pressure storage tank under a sudden pressure structure; Chang 3 and Chang 6 reservoir accumulates in the upper gradual change zone under a gradual changing pressure structure.Horizontally,the surplus pressure controls the plane distribution of oil and gas reservoirs.Both Chang 6 and Chang 7 reservoirs are located in the area with high residual pressure and sufficient charging power, which is conducive to hydrocarbon accumulation. The research is of guiding significance for the future exploration and deployment of tight oil in Yanchang formation of Xunyi block.
Abstract：
On the basis of field investigation, this paper used 13C isotope analysis and differential thermal analysis to determine the metallogenic conditions and genetic types of Wulan crystalline graphite ore in the northern margin of Craton in North China.The average content of graphene 13C is-27.17 ‰,slightly higher than that of the organic matter 13C (-26‰).The maximum exothermal peak of graphite is 726-1 030℃,mainly between 900-1 030℃, showing that the metamorphism of the graphite ore was amphibolite facies and granulite facies.The carbon was from homologous biological organic matter.The characteristic of the deposit and that of mineral combinations deduced that the mineral-bearing structure of graphite ore was a set of typical high-temperature metamorphic aluminium-rich sedimentary rocks. The organic deposits were decomposed and recrystallized by regional metamorphism,forming graphite source beds.The heat source provided by the Hualixi intrusive body increased the flake of the graphite, thus graphite ore enriched and formed at later stage because of ductile shear.
On the basis of field investigation, this paper used 13C isotope analysis and differential thermal analysis to determine the metallogenic conditions and genetic types of Wulan crystalline graphite ore in the northern margin of Craton in North China.The average content of graphene 13C is-27.17 ‰,slightly higher than that of the organic matter 13C (-26‰).The maximum exothermal peak of graphite is 726-1 030℃,mainly between 900-1 030℃, showing that the metamorphism of the graphite ore was amphibolite facies and granulite facies.The carbon was from homologous biological organic matter.The characteristic of the deposit and that of mineral combinations deduced that the mineral-bearing structure of graphite ore was a set of typical high-temperature metamorphic aluminium-rich sedimentary rocks. The organic deposits were decomposed and recrystallized by regional metamorphism,forming graphite source beds.The heat source provided by the Hualixi intrusive body increased the flake of the graphite, thus graphite ore enriched and formed at later stage because of ductile shear.
2021, 54(2): 239-247.
DOI: 10.19751/j.cnki.61-1149/p.2021.02.021
Abstract：
Groundwater quality evaluation is the premise of the protecting and rationally exploiting of groundwater resources.In order to accurately reflect the groundwater quality in Delingha basin,12 general chemical indexes and 4 toxicological indexes were selected using a combination evaluation method of worst index judgment method and improved Nemerow index method, which was based on 66 groups of Quaternary groundwater quality test data in Delingha basin, Qinghai Province.The results show that:①the overall quality of Quaternary groundwater in Delingha basin is good.Samples from grade I-Ⅲ groundwater accounts for 74.24% of the total,and grade IV accounts for 10.61%,grade V for 15.15%. ②The quality of confined (artesian) water in Delingha basin is better than that of phreatic water, and the groundwater quality in the alluvial lacustrine plain areas is better than that in other areas. ③Among the 16 indexes evaluated, 5 indexes,which are sulfate, total hardness, natrium, TDS and chloride, exceed the standard level and the rate of excess is greater than 10%.The major transnormal items are the general chemical indexes in the groundwater,while the 3-nitrogen and toxicological indexes are less exceeding.④The quality of groundwater in this area is more controlled by the original geological and natural environment and less affected by human activities.The specific landform, geological structure and sedimentary environment controlled the formation of aquifer and the cyclic evolution of groundwater,thereby controlling the overall quality of groundwater, while the arid and rainless climate affects the quality of shallow groundwater.
Groundwater quality evaluation is the premise of the protecting and rationally exploiting of groundwater resources.In order to accurately reflect the groundwater quality in Delingha basin,12 general chemical indexes and 4 toxicological indexes were selected using a combination evaluation method of worst index judgment method and improved Nemerow index method, which was based on 66 groups of Quaternary groundwater quality test data in Delingha basin, Qinghai Province.The results show that:①the overall quality of Quaternary groundwater in Delingha basin is good.Samples from grade I-Ⅲ groundwater accounts for 74.24% of the total,and grade IV accounts for 10.61%,grade V for 15.15%. ②The quality of confined (artesian) water in Delingha basin is better than that of phreatic water, and the groundwater quality in the alluvial lacustrine plain areas is better than that in other areas. ③Among the 16 indexes evaluated, 5 indexes,which are sulfate, total hardness, natrium, TDS and chloride, exceed the standard level and the rate of excess is greater than 10%.The major transnormal items are the general chemical indexes in the groundwater,while the 3-nitrogen and toxicological indexes are less exceeding.④The quality of groundwater in this area is more controlled by the original geological and natural environment and less affected by human activities.The specific landform, geological structure and sedimentary environment controlled the formation of aquifer and the cyclic evolution of groundwater,thereby controlling the overall quality of groundwater, while the arid and rainless climate affects the quality of shallow groundwater.
2021, 54(2): 248-258.
DOI: 10.19751/j.cnki.61-1149/p.2021.02.022
Abstract：
In order to reduce the uncertainty of the environmental assessment,this paper constructeda fuzzy groundwater evaluation model on the basis of the trapezoidal fuzzy theory and the monitoring data from 2017 to 2019. Through field investigation the authors revised the exposure parameters for the research of Yimuquan groundwater.The results show that the total health risk of the water source is between 2.959×10-5~1.504×10-4a-1,not exceeding the generally accepted Ⅲ risk level with the credibility of over 55%.However,in the upstream monitoring point,the risk has exceeded the Ⅲ level that should be given more concern.The primary risk substance is Cr because of the richness of Crin the original environment and the long-term exploitation of groundwater.In terms of different receptors,females have a higher risk than males,and adults higher than children.Compared with the traditional model,trapezoidal fuzzy evaluation model can better describe the risk of critical state and is more applicable than the triangular fuzzy model.Trapezoidal fuzzy model and appropriate exposure parametersare important to reduce the uncertainty,though the uncertainty of the model needs further study.
In order to reduce the uncertainty of the environmental assessment,this paper constructeda fuzzy groundwater evaluation model on the basis of the trapezoidal fuzzy theory and the monitoring data from 2017 to 2019. Through field investigation the authors revised the exposure parameters for the research of Yimuquan groundwater.The results show that the total health risk of the water source is between 2.959×10-5~1.504×10-4a-1,not exceeding the generally accepted Ⅲ risk level with the credibility of over 55%.However,in the upstream monitoring point,the risk has exceeded the Ⅲ level that should be given more concern.The primary risk substance is Cr because of the richness of Crin the original environment and the long-term exploitation of groundwater.In terms of different receptors,females have a higher risk than males,and adults higher than children.Compared with the traditional model,trapezoidal fuzzy evaluation model can better describe the risk of critical state and is more applicable than the triangular fuzzy model.Trapezoidal fuzzy model and appropriate exposure parametersare important to reduce the uncertainty,though the uncertainty of the model needs further study.
2021, 54(2): 259-272.
DOI: 10.19751/j.cnki.61-1149/p.2021.02.023
Abstract：
This paper carried out the studies in Bailong river basin,where landslide incidences frequently occurred, to explore the applicability and the rationality of the landslide susceptibility evaluation model.Six indicators of slope, top ographic relief, distance from fault, stratum lithology, watershed gully density and vegetation normalization index were selected assusceptibility evaluation indication. The authors took 2 093 landslide disaster points in the study area as sample data and determined the factor classification status by using the information value, deterministic coefficient value and the mutation law of evidence weight value curve, combined with the frequency ratio curve of the landslide area and the graded area as the criticality of the grading division value. Based on the state grade of each index and correlation analysis, three combination models with logistic regression, of information value method, deterministic coefficient method and evidence weight method were used to evaluate the susceptibility of regional landslide hazard.The three combination models were compared and discussed from the aspects of the results, the applicability and the accuracy.Results show that in the evaluation of regional landslide susceptibility, all the three models are ideal. The prediction accuracy of the combination model of information value method with logistic regressionis better than the other two combination models, with a prediction accuracy of94.6%. The results provide reference for geological disaster prevention and land use in this area.
This paper carried out the studies in Bailong river basin,where landslide incidences frequently occurred, to explore the applicability and the rationality of the landslide susceptibility evaluation model.Six indicators of slope, top ographic relief, distance from fault, stratum lithology, watershed gully density and vegetation normalization index were selected assusceptibility evaluation indication. The authors took 2 093 landslide disaster points in the study area as sample data and determined the factor classification status by using the information value, deterministic coefficient value and the mutation law of evidence weight value curve, combined with the frequency ratio curve of the landslide area and the graded area as the criticality of the grading division value. Based on the state grade of each index and correlation analysis, three combination models with logistic regression, of information value method, deterministic coefficient method and evidence weight method were used to evaluate the susceptibility of regional landslide hazard.The three combination models were compared and discussed from the aspects of the results, the applicability and the accuracy.Results show that in the evaluation of regional landslide susceptibility, all the three models are ideal. The prediction accuracy of the combination model of information value method with logistic regressionis better than the other two combination models, with a prediction accuracy of94.6%. The results provide reference for geological disaster prevention and land use in this area.
Abstract：
In order to study the correlation between different crops and heavy metal elements in the soil and the safety of the soil environment in Guanzhong soilselenium-enrichedareas,the authors selected some different crops i.e.wheat, rapeseed, cabbage, etcand root soils from the selenium-enriched areas of Guanzhong Sanyuan-Yanliang and Huxian for analysis.Through analyzing heavy metal element content in crops and the soil safety,it is concluded that different species of crops have different enrichment characteristics for different heavy metals.Rape shows strong enrichment for heavy metals, while tomatoes and peppers show no enrichment characteristics.The non-polluting soil in Guanzhong selenium-rich areas meets the requirements of the pollution-free agricultural bases.The resultsprovides geochemical references for the development of Guanzhongselenium-enriched soil resources.
In order to study the correlation between different crops and heavy metal elements in the soil and the safety of the soil environment in Guanzhong soilselenium-enrichedareas,the authors selected some different crops i.e.wheat, rapeseed, cabbage, etcand root soils from the selenium-enriched areas of Guanzhong Sanyuan-Yanliang and Huxian for analysis.Through analyzing heavy metal element content in crops and the soil safety,it is concluded that different species of crops have different enrichment characteristics for different heavy metals.Rape shows strong enrichment for heavy metals, while tomatoes and peppers show no enrichment characteristics.The non-polluting soil in Guanzhong selenium-rich areas meets the requirements of the pollution-free agricultural bases.The resultsprovides geochemical references for the development of Guanzhongselenium-enriched soil resources.
Abstract：
Natural disasters as geological disasters, floods,and earthquakes etc frequently occurred worldwide nowadays. The aggravation of the clustered disasters makes it an increasing concern how to reduce the risk of these disasters.This paper carried out a comprehensive assessment on the risk of multi-hazard natural disastersin Xianyang city of Shaanxi province.The results show that the risk zone presents obvious spatial differences.Overall, the risk is much higher along the WeiheValley and the northwestern mid-low hilly areas, spreading mainly in the southeast of Qindu District,the northwestof Wugong county,the urban area of Qianxian county,the eastern urban area of Sanyuan county,the urban area of Chunhua county, Binxian city and Xunyi county.In other regions,the risk of natural disasters is comparatively low.The results provide some references and guidance for the emergency managing and land space planning of Xianyang city.
Natural disasters as geological disasters, floods,and earthquakes etc frequently occurred worldwide nowadays. The aggravation of the clustered disasters makes it an increasing concern how to reduce the risk of these disasters.This paper carried out a comprehensive assessment on the risk of multi-hazard natural disastersin Xianyang city of Shaanxi province.The results show that the risk zone presents obvious spatial differences.Overall, the risk is much higher along the WeiheValley and the northwestern mid-low hilly areas, spreading mainly in the southeast of Qindu District,the northwestof Wugong county,the urban area of Qianxian county,the eastern urban area of Sanyuan county,the urban area of Chunhua county, Binxian city and Xunyi county.In other regions,the risk of natural disasters is comparatively low.The results provide some references and guidance for the emergency managing and land space planning of Xianyang city.
