2009 Vol. 42 No. 2
2009, 42(2): 1-37.
Abstract：
The volcanic orcks form Xixiang Group(nicluding Sunjaihe Formation,Dashigou Formation,and Baimianxia Formation)situated in the middle part of South Qinlnig Mountains were formed during the mid-Neoproteorzoic(730-827Ma)and in an intracontniental rift setting.They are most likely related to the proposed mantle plume that led to the rifting-breakup of the Rodinia supercontinent.
The volcanic orcks form Xixiang Group(nicluding Sunjaihe Formation,Dashigou Formation,and Baimianxia Formation)situated in the middle part of South Qinlnig Mountains were formed during the mid-Neoproteorzoic(730-827Ma)and in an intracontniental rift setting.They are most likely related to the proposed mantle plume that led to the rifting-breakup of the Rodinia supercontinent.
2009, 42(2): 38-47.
Abstract：
Based on the data of geology, geochemistry, geophysics, and deep tectonic evolution, we discuss the double-basement-crystalline-basement (Ar3Pt1),folded-and-metamorphic basement (Pt2-3),cover (NhZ),upper and lower glacigenic rocks, and boundary of blocks in "Western China Block".The "Western China Block" compose of Tarin,Qaidam,China Tianshan, and Dunhuang massif, the middle-north QilianM ountains, A lashan massif.
Based on the data of geology, geochemistry, geophysics, and deep tectonic evolution, we discuss the double-basement-crystalline-basement (Ar3Pt1),folded-and-metamorphic basement (Pt2-3),cover (NhZ),upper and lower glacigenic rocks, and boundary of blocks in "Western China Block".The "Western China Block" compose of Tarin,Qaidam,China Tianshan, and Dunhuang massif, the middle-north QilianM ountains, A lashan massif.
2009, 42(2): 48-54.
Abstract：
Taking Beishan region as the main studying area,the major regulations and characteristics of Mesozoic structural-magmatic activities and mineralization are discussed. It is supposed that the studying area,where mineralization occurred in tensively and widely,had been strongly influenced by geotectonic activities of offshore west Pacific Ocean in the period of Indosinian-Yanshanian which is an important mineralization period. Finally,some thoughts and suggestions for studying prospecting copper and polymetallic depositin this area have been put forward.
Taking Beishan region as the main studying area,the major regulations and characteristics of Mesozoic structural-magmatic activities and mineralization are discussed. It is supposed that the studying area,where mineralization occurred in tensively and widely,had been strongly influenced by geotectonic activities of offshore west Pacific Ocean in the period of Indosinian-Yanshanian which is an important mineralization period. Finally,some thoughts and suggestions for studying prospecting copper and polymetallic depositin this area have been put forward.
Abstract：
The flaggy cherts and argillite in the ophiolitic mélange of Bayingou have a SiO2 content of 55.37%-91.19%,a high Al2O3 content between 3.07%-17.66%,and a TiO2 content of 0.12%-0.8%,having a good positive correlation between Al2O3 and TiO2,suggesting that they have a relatively high percentage of terrigenous muddy sediments Moreover,they have typical NASC-normalized flat REE patterns without any visible Cenegative anomaly;and the Eu has an obvious right-hand dipping pattern.
The flaggy cherts and argillite in the ophiolitic mélange of Bayingou have a SiO2 content of 55.37%-91.19%,a high Al2O3 content between 3.07%-17.66%,and a TiO2 content of 0.12%-0.8%,having a good positive correlation between Al2O3 and TiO2,suggesting that they have a relatively high percentage of terrigenous muddy sediments Moreover,they have typical NASC-normalized flat REE patterns without any visible Cenegative anomaly;and the Eu has an obvious right-hand dipping pattern.
Abstract：
Qingshan gold deposit islocated in Zhen'an Basin of South Qinling.The ore bodies are located above the disconformity between Jiuliping Group and Jiehejie Group,and occuras veins,cystic pattern, lenticular form,and stratified form in the carbonaceous slate and carbonate.The structures of this region inherit the chess board structures formed in Devonian during the early-middle Yanshanian intra-continent oro geny,which control both the location of deposits and the distribution of ore bodies.The ores are divided into primary gold bearing pyrite-siderite type and gossan type.The main metallic mineral in the ore are siderite,pyrite,and limonite.The element association is Au-Ag-As-Sb-Ba,which is consistent to other deposits in the region.The metallogenic temperature ranges from 160℃ to 220℃ and the ore-forming fluid is under ground thermal brine.Therefore,it is the thermal brine that circularly extracts the mineral from the source bed to form this hot spring gold deposit.
Qingshan gold deposit islocated in Zhen'an Basin of South Qinling.The ore bodies are located above the disconformity between Jiuliping Group and Jiehejie Group,and occuras veins,cystic pattern, lenticular form,and stratified form in the carbonaceous slate and carbonate.The structures of this region inherit the chess board structures formed in Devonian during the early-middle Yanshanian intra-continent oro geny,which control both the location of deposits and the distribution of ore bodies.The ores are divided into primary gold bearing pyrite-siderite type and gossan type.The main metallic mineral in the ore are siderite,pyrite,and limonite.The element association is Au-Ag-As-Sb-Ba,which is consistent to other deposits in the region.The metallogenic temperature ranges from 160℃ to 220℃ and the ore-forming fluid is under ground thermal brine.Therefore,it is the thermal brine that circularly extracts the mineral from the source bed to form this hot spring gold deposit.
Abstract：
Several bauxite deposits have been discovered in north area of Wushi,Xinjiang,recently. These bauxite deposits are situated in the edge of passive continent margin of Carboniferous system in south Tianshan where the Ayili River is the bauxite-enriched center,with the o re body stead ily ex tend ing in N E and SWd irections in this region. On the basis of Ayili River ore deposits,we expound the ore-forming geological conditions,bauxite-bearing stratum,and deposit character in this area. The commercial bauxite deposits a reformed in three eroded surfaces of middle carboniferous limestone,dominated by bedded and lenticular ore bodies,whose pattern and size are controlled by the eroded surfaces and ancient landform.
Several bauxite deposits have been discovered in north area of Wushi,Xinjiang,recently. These bauxite deposits are situated in the edge of passive continent margin of Carboniferous system in south Tianshan where the Ayili River is the bauxite-enriched center,with the o re body stead ily ex tend ing in N E and SWd irections in this region. On the basis of Ayili River ore deposits,we expound the ore-forming geological conditions,bauxite-bearing stratum,and deposit character in this area. The commercial bauxite deposits a reformed in three eroded surfaces of middle carboniferous limestone,dominated by bedded and lenticular ore bodies,whose pattern and size are controlled by the eroded surfaces and ancient landform.
2009, 42(2): 83-88.
Abstract：
In this paper,we analyze the data of drilling cores and cast thin sections,study the petrologic characteristics,characteristics of pore and permeability,and the porosity types,and discuss the effect of such factors on oil-bearing layers of Chang-2,Chang-3,Chang-4+5,and Chang-6 in ZHidan area. The resultindicates that the Yanchang reservoir is characterized by low mineral maturity and highst ructure maturity,of which Chang-2,Chang-3,and Chang-4+5 are better than Chang-6 in mineral maturity. The physical property shows that Chang-2 is characterized by middle-sized pores and low permeability while Chang-3,Chang-4+5,and Chang-6 are very low in permeability. Reservoirs are divided in to four types by several parameters,withChang-2 oil-bearing layer containing reservoir type and Chang-6 oil-bearing layers mostly containing reservoir type-Ⅲ.
In this paper,we analyze the data of drilling cores and cast thin sections,study the petrologic characteristics,characteristics of pore and permeability,and the porosity types,and discuss the effect of such factors on oil-bearing layers of Chang-2,Chang-3,Chang-4+5,and Chang-6 in ZHidan area. The resultindicates that the Yanchang reservoir is characterized by low mineral maturity and highst ructure maturity,of which Chang-2,Chang-3,and Chang-4+5 are better than Chang-6 in mineral maturity. The physical property shows that Chang-2 is characterized by middle-sized pores and low permeability while Chang-3,Chang-4+5,and Chang-6 are very low in permeability. Reservoirs are divided in to four types by several parameters,withChang-2 oil-bearing layer containing reservoir type and Chang-6 oil-bearing layers mostly containing reservoir type-Ⅲ.
Abstract：
The analyzing of sediment index is the key technology to research the distribution of sand as to explore the oil-rich area,which is fairly meaningful to the oil exploration.This research area locates in the Wuqi county in the Ordos basin.To start with the analyzing of the well survey materials,according to the observation and description of the core,and with studying of the reginal geological materials,we give a definition and demarcation of the sedimentindex in this area.We define thatitis manly river sedimentin Jurassic,towards the Yan-9,it gradually turned into river and lake delta sediment.We also distinguished the sub-facies and micro-facies.
The analyzing of sediment index is the key technology to research the distribution of sand as to explore the oil-rich area,which is fairly meaningful to the oil exploration.This research area locates in the Wuqi county in the Ordos basin.To start with the analyzing of the well survey materials,according to the observation and description of the core,and with studying of the reginal geological materials,we give a definition and demarcation of the sedimentindex in this area.We define thatitis manly river sedimentin Jurassic,towards the Yan-9,it gradually turned into river and lake delta sediment.We also distinguished the sub-facies and micro-facies.
2009, 42(2): 95-99.
Abstract：
Carbonate rock of Lucaogou Formation in Middle Permian is a major reservoir rock in Santanhu Basin and dolost one accounts for more than 50% in composition of the carbonate rock.There are two types of dolo stone,one is the bedded dolostone and the other is the patch dolomite.In the bedded dolostone,the mineral dolomite has a good idiomorphism;on the contrary,in the patch dolostone,the idiomorphism of dolomite is not good.The patch dolostone is composed of ankerite with crassitude crystal replacing calcite.
Carbonate rock of Lucaogou Formation in Middle Permian is a major reservoir rock in Santanhu Basin and dolost one accounts for more than 50% in composition of the carbonate rock.There are two types of dolo stone,one is the bedded dolostone and the other is the patch dolomite.In the bedded dolostone,the mineral dolomite has a good idiomorphism;on the contrary,in the patch dolostone,the idiomorphism of dolomite is not good.The patch dolostone is composed of ankerite with crassitude crystal replacing calcite.
2009, 42(2): 100-107.
Abstract：
Laumontite cement is widely distributed in the sandstone of Yanchang Formation of Upper Triassic of Ordos basin.Secondary pores dissolved from the laumontite aremajor storage space for oil-gas. By thin-section observation, fluid inclusion analysis, SFNI and energy spectrum analysis, X-diffraction and electron microprobe analysis for clay mineral, we hold that the laumontite of the Yanchang formation is distributed in the delta whose sediments come from the ancient hill in the north-easternOrdos basin.The formation of laumontite is related to sediments formed by volcanic activities and volcanic tuff rock from Yinshan Fold belt. Laumontite shows a pore-filling pattern or being replaced feldspar, whose formation has a multi-stage feature.
Laumontite cement is widely distributed in the sandstone of Yanchang Formation of Upper Triassic of Ordos basin.Secondary pores dissolved from the laumontite aremajor storage space for oil-gas. By thin-section observation, fluid inclusion analysis, SFNI and energy spectrum analysis, X-diffraction and electron microprobe analysis for clay mineral, we hold that the laumontite of the Yanchang formation is distributed in the delta whose sediments come from the ancient hill in the north-easternOrdos basin.The formation of laumontite is related to sediments formed by volcanic activities and volcanic tuff rock from Yinshan Fold belt. Laumontite shows a pore-filling pattern or being replaced feldspar, whose formation has a multi-stage feature.
Abstract：
In our study,we analyzed the drilling and well log data,found seven sequence boundaries,and divided six third-order sequences of the Neopaleozoic sedimentation by using the technology of sedimentology,paleontology,and stratigraphy.On the basis of this,we studied the reason and characteristics of change in eustatic sea level,indicating that the third-order sea level is affected mainly by glacier melt while the fourth-order sea level is formed mainly by the change of the third-order seal evel or the lowering down of phreatic level.
In our study,we analyzed the drilling and well log data,found seven sequence boundaries,and divided six third-order sequences of the Neopaleozoic sedimentation by using the technology of sedimentology,paleontology,and stratigraphy.On the basis of this,we studied the reason and characteristics of change in eustatic sea level,indicating that the third-order sea level is affected mainly by glacier melt while the fourth-order sea level is formed mainly by the change of the third-order seal evel or the lowering down of phreatic level.
2009, 42(2): 116-125.
Abstract：
In order to evaluate the groundwater quality and pollution in Dali county,we carried out the field survey and analysis of the water chemistry from 2006 to 2007.Based on the indexes for third-grade water of the N national groundwater quality standard of China,we selected 12 hydro-chemical components which exceed the standard to assess the groundwater environment quality using the fuzzy-grey evaluation model. The result shows that the majority of water fall the Ⅴ type.Further study indicates that the factors affecting water quality are,from great to small,oxide of iron,chloride,total hardness,fluo ride,total dissolved solid,which are the source of bitter salt water.The high contents of oide of iron,total har dness,total dissolved solid,sulfate,halid are deter mined by geological condition and climate of Dali county,while that of COD,nitrate,nitrite,manganese,and chrome pollutant are mainly caused by human behaviors.
In order to evaluate the groundwater quality and pollution in Dali county,we carried out the field survey and analysis of the water chemistry from 2006 to 2007.Based on the indexes for third-grade water of the N national groundwater quality standard of China,we selected 12 hydro-chemical components which exceed the standard to assess the groundwater environment quality using the fuzzy-grey evaluation model. The result shows that the majority of water fall the Ⅴ type.Further study indicates that the factors affecting water quality are,from great to small,oxide of iron,chloride,total hardness,fluo ride,total dissolved solid,which are the source of bitter salt water.The high contents of oide of iron,total har dness,total dissolved solid,sulfate,halid are deter mined by geological condition and climate of Dali county,while that of COD,nitrate,nitrite,manganese,and chrome pollutant are mainly caused by human behaviors.
