2013 Vol. 38, No. 1
Display Method:
2013, 38(1): 1-9.
doi: 10.3799/dqkx.2013.001
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Abstract:
The first Chinese gas hydrate drilling program was carried out on the Shenhu area in 2007 and obtained gas hydrate samples. In order to understand the strata, age of the zone of gas hydrate occurrence and features of sedimentation rates, Late Miocene to Pleistocene calcareous nanofossil biostratigraphy in 4 holes (SH1B, SH2B, SH5C and SH7B) from the Shenhu gas hydrate drilling area of the northern South China Sea have been studied. A total of 17 Late Miocene to Pleistocene nanofossil events are recognized. The oldest sediments recovered are in an age of late Miocene, younger than 7.362 Ma, and the age assigned for gas hydrate occurrence zone is late Miocene in Hole SH2B and late Miocene to early Pliocene in Hole SH7B. Sedimentation rates varied with holes and times, increasing from Pliocene, and reaching the highest values in Holocene, for example, 1.88-3.27 cm/ka during Pliocene and 20-34.16 cm/ka in Holocene, respectively. Sedimentation rates of 1.88 cm/ka to 4.18 cm/ka were estimated for sediment sequences in gas hydrate occurrence zone. The results suggest that the relationship between sedimentation rates and occurrence of gas hydrates should be more complicated than our earlier knowledge.
The first Chinese gas hydrate drilling program was carried out on the Shenhu area in 2007 and obtained gas hydrate samples. In order to understand the strata, age of the zone of gas hydrate occurrence and features of sedimentation rates, Late Miocene to Pleistocene calcareous nanofossil biostratigraphy in 4 holes (SH1B, SH2B, SH5C and SH7B) from the Shenhu gas hydrate drilling area of the northern South China Sea have been studied. A total of 17 Late Miocene to Pleistocene nanofossil events are recognized. The oldest sediments recovered are in an age of late Miocene, younger than 7.362 Ma, and the age assigned for gas hydrate occurrence zone is late Miocene in Hole SH2B and late Miocene to early Pliocene in Hole SH7B. Sedimentation rates varied with holes and times, increasing from Pliocene, and reaching the highest values in Holocene, for example, 1.88-3.27 cm/ka during Pliocene and 20-34.16 cm/ka in Holocene, respectively. Sedimentation rates of 1.88 cm/ka to 4.18 cm/ka were estimated for sediment sequences in gas hydrate occurrence zone. The results suggest that the relationship between sedimentation rates and occurrence of gas hydrates should be more complicated than our earlier knowledge.
2013, 38(1): 10-24.
doi: 10.3799/dqkx.2013.002
Abstract:
The primary compositions of the anticline core at Shangyupo are Beiyu meta-granitoid, meta-rhyolite and meta-mafic rocks. The age and petrogenesis of the biotite schist have been under debate for a very long time. The petrology features and geochemistry of Shangyupo amphibole/scapolite biotite schist are cricoid gradually distributed from the anticlinal core to its edge. The K, Ca, Na, Rr, Sr and Ba have been changed systematically by the high salinity fluid from the ductile shear belts, and Ta and LREE are also shown to have been dramatically changed in this event. LA-MC-ICPMS zircon U-Pb dating for the Shangyupo meta-rhyolite and the meta-ryholite of Jiangxian group yield the weighted mean 207Pb/206Pb age of 2 160.5±7.8 Ma and 2 161.3±1.5 Ma respectively. The Shangyupo meta-ryhorite and biotite schist may have been formed during the Jiangxian volcano event between 2.20~2.15 Ga, based on the chronology and comparison to related rocks. The HFSE pairs show that the biotite schist is a subalkaline mafic rocks instead of the alkaline mafic rocks as previously suggested. The Jiangxian event may represent a tensional event related to the subduction, based on the comprehensive geological information of Zhongtiaoshan area.
The primary compositions of the anticline core at Shangyupo are Beiyu meta-granitoid, meta-rhyolite and meta-mafic rocks. The age and petrogenesis of the biotite schist have been under debate for a very long time. The petrology features and geochemistry of Shangyupo amphibole/scapolite biotite schist are cricoid gradually distributed from the anticlinal core to its edge. The K, Ca, Na, Rr, Sr and Ba have been changed systematically by the high salinity fluid from the ductile shear belts, and Ta and LREE are also shown to have been dramatically changed in this event. LA-MC-ICPMS zircon U-Pb dating for the Shangyupo meta-rhyolite and the meta-ryholite of Jiangxian group yield the weighted mean 207Pb/206Pb age of 2 160.5±7.8 Ma and 2 161.3±1.5 Ma respectively. The Shangyupo meta-ryhorite and biotite schist may have been formed during the Jiangxian volcano event between 2.20~2.15 Ga, based on the chronology and comparison to related rocks. The HFSE pairs show that the biotite schist is a subalkaline mafic rocks instead of the alkaline mafic rocks as previously suggested. The Jiangxian event may represent a tensional event related to the subduction, based on the comprehensive geological information of Zhongtiaoshan area.
2013, 38(1): 25-32.
doi: 10.3799/dqkx.2013.003
Abstract:
The organic carbon flux to deep ocean, dominated by the bloom of giant "shade flora" diatoms via "fall dump" in stratified ocean, could rival or even exceed that of "spring bloom" diatoms. The giant "shade flora" diatoms played a significant role in the global climate transition and ocean carbon reservoir change in the Quaternary, which could be exploited by the paleoproductivity, one of most important factors in the ocean carbon cycle systems. We tried to estimate the paleoproductivity of laminated Ethmodiscus rex diatom mats (LDM) from tropical West Pacific during the Last Glacial Maximum (LGM), based on the data of opal, total organic carbon and biogenic barium from Core WPD-03 located in the eastern Philippine Sea. Primary productivity, organic carbon rain rates, burial productivity during the LDM deposition were estimated to average 248.42 g·m-2·a-1, 61.93 g·m-2·a-1 and 5.27 g·m-2·a-1, respectively, of which the primary productivity is comparable to those of some modern continent-margin upwelling zones, correcting low primary productivity with a largely stratified ocean and supporting substantial contribution of giant "shade flora" diatoms to the production and export of organic carbon in the world ocean. However, the unreasonable estimations for the export productivity by the empirical formulas in base of photic zone suggest that a caution must be taken to assess the "deep" productivity represented by giant "shade flora" diatoms, which should be distinguishable from classic "surface" productivity characterized by common diatoms. The high levels of productivity of LDM were consistent with the blooming conditions of dust silicon inputs and reducing depositional environments.
The organic carbon flux to deep ocean, dominated by the bloom of giant "shade flora" diatoms via "fall dump" in stratified ocean, could rival or even exceed that of "spring bloom" diatoms. The giant "shade flora" diatoms played a significant role in the global climate transition and ocean carbon reservoir change in the Quaternary, which could be exploited by the paleoproductivity, one of most important factors in the ocean carbon cycle systems. We tried to estimate the paleoproductivity of laminated Ethmodiscus rex diatom mats (LDM) from tropical West Pacific during the Last Glacial Maximum (LGM), based on the data of opal, total organic carbon and biogenic barium from Core WPD-03 located in the eastern Philippine Sea. Primary productivity, organic carbon rain rates, burial productivity during the LDM deposition were estimated to average 248.42 g·m-2·a-1, 61.93 g·m-2·a-1 and 5.27 g·m-2·a-1, respectively, of which the primary productivity is comparable to those of some modern continent-margin upwelling zones, correcting low primary productivity with a largely stratified ocean and supporting substantial contribution of giant "shade flora" diatoms to the production and export of organic carbon in the world ocean. However, the unreasonable estimations for the export productivity by the empirical formulas in base of photic zone suggest that a caution must be taken to assess the "deep" productivity represented by giant "shade flora" diatoms, which should be distinguishable from classic "surface" productivity characterized by common diatoms. The high levels of productivity of LDM were consistent with the blooming conditions of dust silicon inputs and reducing depositional environments.
2013, 38(1): 33-42.
doi: 10.3799/dqkx.2013.004
Abstract:
A three-dimensional (3D) Ocean Bottom Seismometer (OBS) seismic exploration is implemented for the first time in the central sub-basin of South China Sea (SCS). The velocity distribution in 3D high spatial variability is significant to understand the history of expansion and evolution of SCS. However, high-precision 3D data processing determines the resolution and accuracy for the further seismic structure, where OBS position is one of the key parameters in seismic structural study. We use the travel time data of direct water waves to simulate the process of OBS landing on seafloor employing the least squares method and Monte Carlo method. Finally the corrections of OBS positions have been achieved for a total of 39 OBSs in the central sub-basin of SCS experiment. Meanwhile the accuracy of Monte Carlo method for relocation has been discussed. A few clear and reliable P-wave seismic phases, such as Pg, PmP and Pn, were discovered in the OBS seismic record sections, which come from deep crust or upper mantle beneath the Zhenbei-Huangyan volcanic chains. These abundant seismic phases provide a strong data foundation to the further modeling of 3D tomography for the central sub-basin of SCS.
A three-dimensional (3D) Ocean Bottom Seismometer (OBS) seismic exploration is implemented for the first time in the central sub-basin of South China Sea (SCS). The velocity distribution in 3D high spatial variability is significant to understand the history of expansion and evolution of SCS. However, high-precision 3D data processing determines the resolution and accuracy for the further seismic structure, where OBS position is one of the key parameters in seismic structural study. We use the travel time data of direct water waves to simulate the process of OBS landing on seafloor employing the least squares method and Monte Carlo method. Finally the corrections of OBS positions have been achieved for a total of 39 OBSs in the central sub-basin of SCS experiment. Meanwhile the accuracy of Monte Carlo method for relocation has been discussed. A few clear and reliable P-wave seismic phases, such as Pg, PmP and Pn, were discovered in the OBS seismic record sections, which come from deep crust or upper mantle beneath the Zhenbei-Huangyan volcanic chains. These abundant seismic phases provide a strong data foundation to the further modeling of 3D tomography for the central sub-basin of SCS.
2013, 38(1): 43-56.
doi: 10.3799/dqkx.2013.005
Abstract:
Two contrasting models have been proposed to explain the large-scale gold mineralization in the Xiaoqinling gold district, which is the second largest gold producer in China. The first model advocates that gold deposits in the Xiaoqinling district formed in the Triassic in relation to continental collision of the Qinling Orogen, whereas the second indicates that gold mineralization occurred in the Early Cretaceous and was genetically related to lithospheric thinning of the North China Craton. In this paper, we present high precision monazite U-Th-Pb ages of the Qinnan gold deposit in the north metallogenic belt of the Xiaoqinling district, by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Petrographic observations show the monazite occurs as euhedral grains and invariably intergrown with quartz and pyrite, suggesting that monazites are of hydrothermal origin and precipitate with gold-bearing minerals coevally. In the 206Pb/238U-207Pb/235U and 206Pb/238U-208Pb/232Th diagrams, all of the 13 analyses are concordant or nearly concordant, with weighted mean 206Pb/238U and 208Pb/232Th ages of 120.9±0.9 Ma (MSWD=1.0) and 122.6±1.9 Ma (MSWD=2.6), respectively. These ages are reproducible with existing geochronological data for major gold deposits in the Xiaoqinling district, demonstrating that the U-Th-Pb isotopes of the monazite have remained closed since its precipitation, and thus the U-Th-Pb ages can be reliably interpreted as the mineralizing age of the Qinnan gold deposit. A synthesis of available age constraints suggests that gold mineralization throughout the Xiaoqinling district occurred with a relatively short time interval in the Early Cretaceous and was likely related to the lithospheric thinning of the North China Craton at that time.
Two contrasting models have been proposed to explain the large-scale gold mineralization in the Xiaoqinling gold district, which is the second largest gold producer in China. The first model advocates that gold deposits in the Xiaoqinling district formed in the Triassic in relation to continental collision of the Qinling Orogen, whereas the second indicates that gold mineralization occurred in the Early Cretaceous and was genetically related to lithospheric thinning of the North China Craton. In this paper, we present high precision monazite U-Th-Pb ages of the Qinnan gold deposit in the north metallogenic belt of the Xiaoqinling district, by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Petrographic observations show the monazite occurs as euhedral grains and invariably intergrown with quartz and pyrite, suggesting that monazites are of hydrothermal origin and precipitate with gold-bearing minerals coevally. In the 206Pb/238U-207Pb/235U and 206Pb/238U-208Pb/232Th diagrams, all of the 13 analyses are concordant or nearly concordant, with weighted mean 206Pb/238U and 208Pb/232Th ages of 120.9±0.9 Ma (MSWD=1.0) and 122.6±1.9 Ma (MSWD=2.6), respectively. These ages are reproducible with existing geochronological data for major gold deposits in the Xiaoqinling district, demonstrating that the U-Th-Pb isotopes of the monazite have remained closed since its precipitation, and thus the U-Th-Pb ages can be reliably interpreted as the mineralizing age of the Qinnan gold deposit. A synthesis of available age constraints suggests that gold mineralization throughout the Xiaoqinling district occurred with a relatively short time interval in the Early Cretaceous and was likely related to the lithospheric thinning of the North China Craton at that time.
2013, 38(1): 57-67.
doi: 10.3799/dqkx.2013.006
Abstract:
The SHRIMP zircon U-Pb dating of granodiorite-porphyry, the main rock type of Anjishan rock mass yields the age of 106.9±0.9 Ma, as the formation age of the Anjishan rock mass, which shows that the Anjishan rock mass formed in the late Early Cretaceous. Anjishan rock mass is younger than the high-K calc-alkaline intermediate-acidic intrusive rocks in Tongling and other districts and it illustrates that the intermediate-acidic intrusive rocks in Ningzhen District belongs to another diagenetic event in the middle to lower Yangtze metallogenic belt's Mesozoic large magmatism. The Ningzhen District's Cu-polymetallic mineralization is closely related with the 107 Ma calc-alkaline intermediate-acidic magmatism in time, space and origin. The petrogenesis- mineralization has been a continuous process in this district. The geodynamics background of the Ningzhen District's calc-alkaline intermediate-acidic magmatism corresponds to the Mesozoic lithospheric delamination thinning event in Eastern China. It demonstrates that the middle to lower Yangtze lithosphere delamination began at about130 Ma, and lasted to 107 Ma or later.
The SHRIMP zircon U-Pb dating of granodiorite-porphyry, the main rock type of Anjishan rock mass yields the age of 106.9±0.9 Ma, as the formation age of the Anjishan rock mass, which shows that the Anjishan rock mass formed in the late Early Cretaceous. Anjishan rock mass is younger than the high-K calc-alkaline intermediate-acidic intrusive rocks in Tongling and other districts and it illustrates that the intermediate-acidic intrusive rocks in Ningzhen District belongs to another diagenetic event in the middle to lower Yangtze metallogenic belt's Mesozoic large magmatism. The Ningzhen District's Cu-polymetallic mineralization is closely related with the 107 Ma calc-alkaline intermediate-acidic magmatism in time, space and origin. The petrogenesis- mineralization has been a continuous process in this district. The geodynamics background of the Ningzhen District's calc-alkaline intermediate-acidic magmatism corresponds to the Mesozoic lithospheric delamination thinning event in Eastern China. It demonstrates that the middle to lower Yangtze lithosphere delamination began at about130 Ma, and lasted to 107 Ma or later.
2013, 38(1): 68-86.
doi: 10.3799/dqkx.2013.007
Abstract:
Zhoukoudian intrusion contains intermediate-acidic rocks with three magmatic pulses. LA-ICPMS zircon U-Pb ages of quartz diorite and diorite-porphyry are 131.6±2.1 Ma and 128.1±1.4 Ma, respectively. All kinds of rocks are metaluminous and show high-K calc-alkaline affinity with high Mg#. Their LREE, Ba, K, and Sr contents are high and HREE, Ta, Nb, P, and Ti are low with no Eu anomaly, high (La/Yb)N and Sr/Y ratios. Zoned plagioclase with large mantle is common in granodiorite (second pulse) and mafic microgranular enclaves. Two such zoned plagioclase crystals are studied: One from granodiorite with high An compositions in cores and reverse-, normal-zoning outwardly in well-developed mantles; the other from mafic microgranular enclave with low An compositions in cores and beginning with dusty zoning and then showing normal-zoning in mantles, together with shape, size, quantity, reverse vein, statistics of mineral contents, mineral compositions, geochemistry, zoned structure, dyke-like swarms of mafic microgranular enclaves, a genesis of magma mingling between basic and acid magma is suggested. Magma mingling attained local equilibrium around enclaves and happened during whole solidified process of granodiorite due to multiple pulses of basic magma. The rocks from Zhoukoudian intrusion are adakitic and are partially melted within thickened lower crust. (Er/Lu)N and Nb/Ta ratios increase from quartz diorite-granodiorite to intermediate-acidic dykes, which indicates that residual minerals in source region changed from amphibole+garnet to garnet+rutile and the source became deeper.
Zhoukoudian intrusion contains intermediate-acidic rocks with three magmatic pulses. LA-ICPMS zircon U-Pb ages of quartz diorite and diorite-porphyry are 131.6±2.1 Ma and 128.1±1.4 Ma, respectively. All kinds of rocks are metaluminous and show high-K calc-alkaline affinity with high Mg#. Their LREE, Ba, K, and Sr contents are high and HREE, Ta, Nb, P, and Ti are low with no Eu anomaly, high (La/Yb)N and Sr/Y ratios. Zoned plagioclase with large mantle is common in granodiorite (second pulse) and mafic microgranular enclaves. Two such zoned plagioclase crystals are studied: One from granodiorite with high An compositions in cores and reverse-, normal-zoning outwardly in well-developed mantles; the other from mafic microgranular enclave with low An compositions in cores and beginning with dusty zoning and then showing normal-zoning in mantles, together with shape, size, quantity, reverse vein, statistics of mineral contents, mineral compositions, geochemistry, zoned structure, dyke-like swarms of mafic microgranular enclaves, a genesis of magma mingling between basic and acid magma is suggested. Magma mingling attained local equilibrium around enclaves and happened during whole solidified process of granodiorite due to multiple pulses of basic magma. The rocks from Zhoukoudian intrusion are adakitic and are partially melted within thickened lower crust. (Er/Lu)N and Nb/Ta ratios increase from quartz diorite-granodiorite to intermediate-acidic dykes, which indicates that residual minerals in source region changed from amphibole+garnet to garnet+rutile and the source became deeper.
2013, 38(1): 87-93.
doi: 10.3799/dqkx.2013.008
Abstract:
Coalbed methane (CBM) accumulation models include continuous gas accumulation and staged gas accumulation. However, the study on geochemistry characteristics and evaluation index of staged accumulation CBM is inadequate. This study has obtained the carbon and hydrogen isotopic compositions and their evolution laws of methane and ethane generated at different evolution stages by thermal simulation of samples prepared using a forest marsh peat at different temperatures. The data show that the carbon and hydrogen isotopic compositions tend to increase heavy isotope with increasing evolution level of the starting sample. At the same time, it is found that the maturity level of the starting sample influences the carbon isotopic compositions of methane and ethane, while maturity of gases affects their hydrogen isotopic compositions. The relationship between Ro values and the carbon and hydrogen isotopic compositions of gases generated by coal-forming organic matter at different evolution stages as well as the carbon or hydrogen isotopic relationship between methane and ethane are established. These results provide scientific evidence for studying the genesis of CBM generated at different maturity intervals and understanding the geochemistry characteristics of staged accumulation CBM, and they were applied to study on CBM from the southern Qinshui basin, and it is found that it accumulated after Middle Jurassic and is characterized by staged gas accumulation, which indicates that the results of thermal simulation experiments are very important for judging the genesis of natural CBM.
Coalbed methane (CBM) accumulation models include continuous gas accumulation and staged gas accumulation. However, the study on geochemistry characteristics and evaluation index of staged accumulation CBM is inadequate. This study has obtained the carbon and hydrogen isotopic compositions and their evolution laws of methane and ethane generated at different evolution stages by thermal simulation of samples prepared using a forest marsh peat at different temperatures. The data show that the carbon and hydrogen isotopic compositions tend to increase heavy isotope with increasing evolution level of the starting sample. At the same time, it is found that the maturity level of the starting sample influences the carbon isotopic compositions of methane and ethane, while maturity of gases affects their hydrogen isotopic compositions. The relationship between Ro values and the carbon and hydrogen isotopic compositions of gases generated by coal-forming organic matter at different evolution stages as well as the carbon or hydrogen isotopic relationship between methane and ethane are established. These results provide scientific evidence for studying the genesis of CBM generated at different maturity intervals and understanding the geochemistry characteristics of staged accumulation CBM, and they were applied to study on CBM from the southern Qinshui basin, and it is found that it accumulated after Middle Jurassic and is characterized by staged gas accumulation, which indicates that the results of thermal simulation experiments are very important for judging the genesis of natural CBM.
2013, 38(1): 94-104.
doi: 10.3799/dqkx.2013.009
Abstract:
The Carboniferous oil in the Tazhong-4 Oilfield situated in the tectonic high of the Tazhong uplift, is quite different from the surrounding oil. High resolution mass spectrum and GC-MS is utilized to reveal the genetic mechanism of the oil. It is observed that the Tazhong-4 oil are abundant in both n-alkanes (suggesting no or little biodegradation) and biodegraded tricyclic terpanes as well as 25-norhopanes (indicating strong biodegradation) based on GC-MS analysis, which suggests multiple phases of petroleum charging in the area. No abnormal sulfur compounds are detected from the Tazhong-4 oils by FT-ICR MS, namely little sulfur compounds with low values of double-bond equivalent (DBE) detected, and no abnormality is observed for the gases associated with the Tazhong oil from views of both the composition as well as distribution and the stable carbon isotope, which suggests no or little TSR alteration of the Tazhong-4 Carboniferous oil. It is also found that the composition and relative distribution of the sulfur compounds in the Tazhong-4 oilfield is similar to that of the majority of the Lower Ordovician oil, suggesting a genetic affinity between them. It has been testified by experiments that oil-mixing of deep oil such as the Low Ordovician oil with the shallow oil could result in a kind of high dibenzothiophen (DBT) oil like the Tazhong-4 oil. After a comprehensive geochemical and geological investigation, we believe that it was deep oil-mixing that caused the unusually high DBT oil in the Tazhong-4 oilfield rather than TSR.
The Carboniferous oil in the Tazhong-4 Oilfield situated in the tectonic high of the Tazhong uplift, is quite different from the surrounding oil. High resolution mass spectrum and GC-MS is utilized to reveal the genetic mechanism of the oil. It is observed that the Tazhong-4 oil are abundant in both n-alkanes (suggesting no or little biodegradation) and biodegraded tricyclic terpanes as well as 25-norhopanes (indicating strong biodegradation) based on GC-MS analysis, which suggests multiple phases of petroleum charging in the area. No abnormal sulfur compounds are detected from the Tazhong-4 oils by FT-ICR MS, namely little sulfur compounds with low values of double-bond equivalent (DBE) detected, and no abnormality is observed for the gases associated with the Tazhong oil from views of both the composition as well as distribution and the stable carbon isotope, which suggests no or little TSR alteration of the Tazhong-4 Carboniferous oil. It is also found that the composition and relative distribution of the sulfur compounds in the Tazhong-4 oilfield is similar to that of the majority of the Lower Ordovician oil, suggesting a genetic affinity between them. It has been testified by experiments that oil-mixing of deep oil such as the Low Ordovician oil with the shallow oil could result in a kind of high dibenzothiophen (DBT) oil like the Tazhong-4 oil. After a comprehensive geochemical and geological investigation, we believe that it was deep oil-mixing that caused the unusually high DBT oil in the Tazhong-4 oilfield rather than TSR.
2013, 38(1): 105-111.
doi: 10.3799/dqkx.2013.010
Abstract:
Evolution history of abnormal formation pressure is vital to further understanding of the dynamic processes of hydrocarbon generation, migration and accumulation. In order to reveal the evolution features of the abnormal formation pressure in Linnan Sag, thermodynamic modeling in accordance with concepts of fluid inclusion assemblage was employed to reconstruct the palaeopressures of the third member, Shahejie Formation. The evolution of formation pressure coefficients with time suggest that there had already developed overpressures at about 30 Ma in the middle and the lower sections of the third member of Shahejie Formation, and the whole evolution since 30 Ma shows a cyclic feature of pressure decreasing, increasing and decreasing. Underpressure was the result of overpressure evolution to the later period of that time. There was no overpressure developed in the upper section of the third member of Shahejie Formation during that time, but there was an obvious pressure decreasing trend during the later period of the whole evolution. Considering the hydrocarbon generation and charge histories, and the fault activities, integrated analysis indicate that overpressure was mainly caused and controlled by hydrocarbon generating and charging in the earlier time, while underpressure was mainly caused and controlled by multiple times and long-term activities of the faults, especially in the later time.
Evolution history of abnormal formation pressure is vital to further understanding of the dynamic processes of hydrocarbon generation, migration and accumulation. In order to reveal the evolution features of the abnormal formation pressure in Linnan Sag, thermodynamic modeling in accordance with concepts of fluid inclusion assemblage was employed to reconstruct the palaeopressures of the third member, Shahejie Formation. The evolution of formation pressure coefficients with time suggest that there had already developed overpressures at about 30 Ma in the middle and the lower sections of the third member of Shahejie Formation, and the whole evolution since 30 Ma shows a cyclic feature of pressure decreasing, increasing and decreasing. Underpressure was the result of overpressure evolution to the later period of that time. There was no overpressure developed in the upper section of the third member of Shahejie Formation during that time, but there was an obvious pressure decreasing trend during the later period of the whole evolution. Considering the hydrocarbon generation and charge histories, and the fault activities, integrated analysis indicate that overpressure was mainly caused and controlled by hydrocarbon generating and charging in the earlier time, while underpressure was mainly caused and controlled by multiple times and long-term activities of the faults, especially in the later time.
2013, 38(1): 112-120.
doi: 10.3799/dqkx.2013.010
Abstract:
Huizhou depression is one of the major petroleum contribution areas in Pearl River Mouth basin, and it is significant to the research of abundant hydrocarbon depression with the further confirmation of source rock characteristics and petroleum resources. Comprehensive analysis of the abundance, type, maturity of organic matter, effective thickness, organic carbon recovery factor and production rate, shows that Paleogene Wenchang formation and Enping formation are good source rocks. The quantitative prediction technology of source rock TOC seismic data makes up for the lack of less core and measured sample discontinuous distribution. TOC seismic data predict quantitatively TOC contents and variations in the different depths and different time planes, which has laid a good foundation for the more accurate assessment of source rocks and petroleum resources. Based on the quantitative prediction technology of source rock TOC seismic data and the basic stratigraphy unit of third-order sequence, that, petroleum resources quantities of Paleogene source rocks through the genetic method in Huizhou Depression, are 1.698 times last one. The Paleogene transfer zones which are close to source rocks have the advantage of near-source for hydrocarbons with great exploration potential.
Huizhou depression is one of the major petroleum contribution areas in Pearl River Mouth basin, and it is significant to the research of abundant hydrocarbon depression with the further confirmation of source rock characteristics and petroleum resources. Comprehensive analysis of the abundance, type, maturity of organic matter, effective thickness, organic carbon recovery factor and production rate, shows that Paleogene Wenchang formation and Enping formation are good source rocks. The quantitative prediction technology of source rock TOC seismic data makes up for the lack of less core and measured sample discontinuous distribution. TOC seismic data predict quantitatively TOC contents and variations in the different depths and different time planes, which has laid a good foundation for the more accurate assessment of source rocks and petroleum resources. Based on the quantitative prediction technology of source rock TOC seismic data and the basic stratigraphy unit of third-order sequence, that, petroleum resources quantities of Paleogene source rocks through the genetic method in Huizhou Depression, are 1.698 times last one. The Paleogene transfer zones which are close to source rocks have the advantage of near-source for hydrocarbons with great exploration potential.
2013, 38(1): 121-129.
doi: 10.3799/dqkx.2013.012
Abstract:
Due to insufficient well data, the diversity of sediment transport pathway and their controlling deposits was analyzed using the recent 3D seismic data in the western slope of Bozhong sag. The results show that there are three types of sediment transport pathway in Dongying formation of the western slope of Bozhong sag, including sediment transport pathway of Paleo-channel, faulted trough and structural transfer zones. The deposits of study area were controlled mainly by faulted trough sediment transport pathway derived from Shaleitian uplift, with the belted distribution in NEE direction. The deposits controlled by paleo-channel sediment transport pathway occurred in the local area of southern Shijiutuo uplift. The deposits controlled by structural transfer zones sediment transport pathway are focused on the local area of southeast Shaleitian uplift. Three types of sediment transport pathway display the overall sediment transport methods from the source area to the deposits area in the continental lacustrine basins, and formed three types corresponding coupling patterns of the source area- transport pathway-deposit area. Structural transfer zones sediment transport pathway is considered one special style of faulted trough sediment transport pathway. The presence of faulted trough sediment transport pathway derived from the Shaleitian uplift changes the past understanding that it is the fan delta with proximal and rapid deposit in the eastern Shaleitian uplift, and provides an effective model for seeking potential reservoir.
Due to insufficient well data, the diversity of sediment transport pathway and their controlling deposits was analyzed using the recent 3D seismic data in the western slope of Bozhong sag. The results show that there are three types of sediment transport pathway in Dongying formation of the western slope of Bozhong sag, including sediment transport pathway of Paleo-channel, faulted trough and structural transfer zones. The deposits of study area were controlled mainly by faulted trough sediment transport pathway derived from Shaleitian uplift, with the belted distribution in NEE direction. The deposits controlled by paleo-channel sediment transport pathway occurred in the local area of southern Shijiutuo uplift. The deposits controlled by structural transfer zones sediment transport pathway are focused on the local area of southeast Shaleitian uplift. Three types of sediment transport pathway display the overall sediment transport methods from the source area to the deposits area in the continental lacustrine basins, and formed three types corresponding coupling patterns of the source area- transport pathway-deposit area. Structural transfer zones sediment transport pathway is considered one special style of faulted trough sediment transport pathway. The presence of faulted trough sediment transport pathway derived from the Shaleitian uplift changes the past understanding that it is the fan delta with proximal and rapid deposit in the eastern Shaleitian uplift, and provides an effective model for seeking potential reservoir.
2013, 38(1): 130-142.
doi: 10.3799/dqkx.2013.013
Abstract:
Determination of the effects of diagenesis on Dainan sandstone reservoir in Zhenwu-Caozhuang region can facilitate the prediction of the beneficial oil reservoir. Based on core observation, the diagenetic characteristics of Dainan reservoir has been studied in detail by using case thin section, SEM, mercury penetration, X-ray and buried-thermal history modeling. Dainan sandstone has experienced such processes as the compaction, cementation, dissolution and metasomatism. Authigenetic cement includes clay mineral, ferrum carbonate, quartz, feldspar and anhydrite. Feldspar and fragment have mainly suffered dissolution. Dainan Formation is in the period A of mesodiagenesis. Dainan reservoir quality is mainly controlled by compaction, kaolinite cementation, ferrum carbonate cementation, overgrowth quartz and dissolution. Sandstone reservoirs in which dissolution or kaolinite infill diagenentic lithofacies develop commonly have higher porosity and permeability, while reservoirs developing compact-filling or carbonate cementation diagenentic lithofacies usually have poor physical property.
Determination of the effects of diagenesis on Dainan sandstone reservoir in Zhenwu-Caozhuang region can facilitate the prediction of the beneficial oil reservoir. Based on core observation, the diagenetic characteristics of Dainan reservoir has been studied in detail by using case thin section, SEM, mercury penetration, X-ray and buried-thermal history modeling. Dainan sandstone has experienced such processes as the compaction, cementation, dissolution and metasomatism. Authigenetic cement includes clay mineral, ferrum carbonate, quartz, feldspar and anhydrite. Feldspar and fragment have mainly suffered dissolution. Dainan Formation is in the period A of mesodiagenesis. Dainan reservoir quality is mainly controlled by compaction, kaolinite cementation, ferrum carbonate cementation, overgrowth quartz and dissolution. Sandstone reservoirs in which dissolution or kaolinite infill diagenentic lithofacies develop commonly have higher porosity and permeability, while reservoirs developing compact-filling or carbonate cementation diagenentic lithofacies usually have poor physical property.
2013, 38(1): 143-155.
doi: 10.3799/dqkx.2013.014
Abstract:
The accuracy of trapping pressure reconstruction using petroleum inclusion thermodynamic modeling is largely controlled by the accuracy of composition model and the prediction of saturation pressure and gas-liquid phase mole volume of petroleum fluid besides the measured parameters including homogenization temperature of petroleum inclusion (Th, oil), homogenization temperature of aqueous fluid inclusion (Th, aqu) and the degree of bubble filling (Fv). On condition that improving the α-β composition model, the saturation pressure predicition of α-β petroleum fluid has been improved and verified by adjusting the composition and matching the saturation pressure. The Isochore and the degree of bubble filling (Fv) of petroleum inclusion at room temperature have been improved by matching the 391 relative volume data of the constant composition expansion experiment of 22 reservoir fluids using the Peng-Robinson equation of state (EoS) under match of saturation pressure. Finally, the accuracies of trapping pressure reconstruction using the proposed method, PIT software and Vtflinc software have been evaluated by two constraining conditions for composition modeling, one is methane mole content of true petroleum fluid and the other is methane mole content from the equivalent petroleum fluid. The results show that the improved petroleum inclusions thermodynamic modeling method can effectively increase the accuracy of trapping pressure reconstruction by comparing the PIT software and Vtflinc software. Taking into consideration of the difficulty in obtaining the methane mole content of petroleum inclusion, the best recommended method to reconstruct the trapping pressure is using the composition of equivalent petroleum fluid contain the petroleum inclusions thermodynamic modeling using this method.
The accuracy of trapping pressure reconstruction using petroleum inclusion thermodynamic modeling is largely controlled by the accuracy of composition model and the prediction of saturation pressure and gas-liquid phase mole volume of petroleum fluid besides the measured parameters including homogenization temperature of petroleum inclusion (Th, oil), homogenization temperature of aqueous fluid inclusion (Th, aqu) and the degree of bubble filling (Fv). On condition that improving the α-β composition model, the saturation pressure predicition of α-β petroleum fluid has been improved and verified by adjusting the composition and matching the saturation pressure. The Isochore and the degree of bubble filling (Fv) of petroleum inclusion at room temperature have been improved by matching the 391 relative volume data of the constant composition expansion experiment of 22 reservoir fluids using the Peng-Robinson equation of state (EoS) under match of saturation pressure. Finally, the accuracies of trapping pressure reconstruction using the proposed method, PIT software and Vtflinc software have been evaluated by two constraining conditions for composition modeling, one is methane mole content of true petroleum fluid and the other is methane mole content from the equivalent petroleum fluid. The results show that the improved petroleum inclusions thermodynamic modeling method can effectively increase the accuracy of trapping pressure reconstruction by comparing the PIT software and Vtflinc software. Taking into consideration of the difficulty in obtaining the methane mole content of petroleum inclusion, the best recommended method to reconstruct the trapping pressure is using the composition of equivalent petroleum fluid contain the petroleum inclusions thermodynamic modeling using this method.
2013, 38(1): 156-164.
doi: 10.3799/dqkx.2013.015
Abstract:
To further understand the genetic types of the tight sandstone gas reservoirs in Kuqa depression, the core from tight sandstone gas reservoirs is sampled to carry out the analysis on hydrocarbon charge history and porosity evolution. The hydrocarbon charge history is investigated by analyzing the fluid inclusion petrography, and microther mometry and the porosity evolution is restored by using the model of deposition-structure -diagenesis. Combining with gas-water relationship and distribution of tight sandstone gas reservoirs. There are two charge events in the YN2 Jurassic tight sandstone reservoir, with the one of oil charge during 23-12 Ma, and the other gas charge during 5-0 Ma. The reservoir porosity dropped to less than 12% and became tight during the period of 12-8 Ma. Two charge events have been recorded in the DN2 Paleogene tight sandstone reservoir; the former is oil charge during 23-12 Ma, and the latter is the gas charge during 5-0 Ma. The reservoir porosity dropped to less than 12% during the period of 2-0 Ma and became tight later. Two genetic types of tight sandstone gas reservoirs have been confirmed. The YN2 Jurassic tight sandstone reservoir is of the genetic type of "tight deep basin gas reservoir" with the accumulation process of gas charge after the reservoir tightened and the DN2 Paleogene tight sandstone reservoir is defined as "tight conventional gas reservoir" with the accumulation process of gas charge before the reservoir tightened. This study is of significance for further exploration and exploitation of tight sandstone gas in Kuqa depression.
To further understand the genetic types of the tight sandstone gas reservoirs in Kuqa depression, the core from tight sandstone gas reservoirs is sampled to carry out the analysis on hydrocarbon charge history and porosity evolution. The hydrocarbon charge history is investigated by analyzing the fluid inclusion petrography, and microther mometry and the porosity evolution is restored by using the model of deposition-structure -diagenesis. Combining with gas-water relationship and distribution of tight sandstone gas reservoirs. There are two charge events in the YN2 Jurassic tight sandstone reservoir, with the one of oil charge during 23-12 Ma, and the other gas charge during 5-0 Ma. The reservoir porosity dropped to less than 12% and became tight during the period of 12-8 Ma. Two charge events have been recorded in the DN2 Paleogene tight sandstone reservoir; the former is oil charge during 23-12 Ma, and the latter is the gas charge during 5-0 Ma. The reservoir porosity dropped to less than 12% during the period of 2-0 Ma and became tight later. Two genetic types of tight sandstone gas reservoirs have been confirmed. The YN2 Jurassic tight sandstone reservoir is of the genetic type of "tight deep basin gas reservoir" with the accumulation process of gas charge after the reservoir tightened and the DN2 Paleogene tight sandstone reservoir is defined as "tight conventional gas reservoir" with the accumulation process of gas charge before the reservoir tightened. This study is of significance for further exploration and exploitation of tight sandstone gas in Kuqa depression.
2013, 38(1): 165-172.
doi: 10.3799/dqkx.2013.016
Abstract:
The formation and distribution of hydrocarbon accumulation are controlled by the fluid potential in oil-bearing basin. The distribution characteristics of discovered hydrocarbon accumulation in the Jiyang superdepression show that hydrocarbon could only be accumulated in the reservoir rock where the potential varies from 2 to 100 times of the potential of the surrounding rock. A certain critical value of porosity is necessary for hydrocarbon accumulation in depth. The research also suggests that the porosity decreases and the critical formation condition of hydrocarbon accumulation changes with the burial depth. The trap in the deep burial depth should meet the condition of relatively lower potential compared with the trap in the shallow burial depth. The dynamic analysis and physical experiments also show that the premise condition of hydrocarbon accumulation in the surface of the earth is pore radii in the reservoir rock is double of that in the surrounding rock. The premise condition of hydrocarbon accumulation in the underground reservoir rock is the capillary pressure disparity higher than the sum of capillary pressure and the stratigraphic pressure in the reservoir., which suggests that the lower potential in the trap would cause the higher oil saturation and resources in the reservoir. The characteristics and dynamic analysis suggest that hydrocarbon can be accumulated in the deeper reservoir with low porosity and permeability only if the physical property of reservoir is better than that of the surrounding mudstone, which could extend the hydrocarbon exploration domain and depth. The characteristics also suggest that sand with relative low porosity and permeability can be cap rocks for sand with relatively high porosity and permeability, which could broaden the favorable exploration area in the shallow strata.
The formation and distribution of hydrocarbon accumulation are controlled by the fluid potential in oil-bearing basin. The distribution characteristics of discovered hydrocarbon accumulation in the Jiyang superdepression show that hydrocarbon could only be accumulated in the reservoir rock where the potential varies from 2 to 100 times of the potential of the surrounding rock. A certain critical value of porosity is necessary for hydrocarbon accumulation in depth. The research also suggests that the porosity decreases and the critical formation condition of hydrocarbon accumulation changes with the burial depth. The trap in the deep burial depth should meet the condition of relatively lower potential compared with the trap in the shallow burial depth. The dynamic analysis and physical experiments also show that the premise condition of hydrocarbon accumulation in the surface of the earth is pore radii in the reservoir rock is double of that in the surrounding rock. The premise condition of hydrocarbon accumulation in the underground reservoir rock is the capillary pressure disparity higher than the sum of capillary pressure and the stratigraphic pressure in the reservoir., which suggests that the lower potential in the trap would cause the higher oil saturation and resources in the reservoir. The characteristics and dynamic analysis suggest that hydrocarbon can be accumulated in the deeper reservoir with low porosity and permeability only if the physical property of reservoir is better than that of the surrounding mudstone, which could extend the hydrocarbon exploration domain and depth. The characteristics also suggest that sand with relative low porosity and permeability can be cap rocks for sand with relatively high porosity and permeability, which could broaden the favorable exploration area in the shallow strata.
2013, 38(1): 173-180.
doi: 10.3799/dqkx.2013.017
Abstract:
The pathways of hydrocarbon migration in main hydrocarbon accumulation periods of Nanpu Depression in Bohai Bay Basin were reconstructed by the technology of streamline simulation. Based on the data of nitrogen compounds and maturity in crude oil, the traced pathways of hydrocarbon migration in the typical enrichment areas are studied. Streamline simulation results show that to reservoir inside and under source rock in south sags, there was a smaller scale hydrocarbon migration in late Dongying Formation (24.6 Ma ago), and a mass hydrocarbon migration in middle Minghuazhen Formation (9 Ma ago). To reservoir upper source rock in south sags and reservoir inside source rock in north sag, there was a small amount of hydrocarbon migration in middle Minghuazhen Formation, mass hydrocarbon migration in late Minghuazhen Formation (2 Ma ago). At present, hydrocarbon distribution in south sags does not match the simulation results, which indicates greater potential for exploration. The geochemical index of crude oil show that in the enrichment area of reservoir upper source rock, hydrocarbon migration was along faults strike, to the tectonic high position and sandstone on both sides of fault plane when the source fault stretched into the Sag center. For source faults parallel to the Sag center, hydrocarbon migration was along the faults tendency to the tectonic high position. In the enrichment area of reservoir inside source rock, hydrocarbon migration was along sandstone to the tectonic high position.
The pathways of hydrocarbon migration in main hydrocarbon accumulation periods of Nanpu Depression in Bohai Bay Basin were reconstructed by the technology of streamline simulation. Based on the data of nitrogen compounds and maturity in crude oil, the traced pathways of hydrocarbon migration in the typical enrichment areas are studied. Streamline simulation results show that to reservoir inside and under source rock in south sags, there was a smaller scale hydrocarbon migration in late Dongying Formation (24.6 Ma ago), and a mass hydrocarbon migration in middle Minghuazhen Formation (9 Ma ago). To reservoir upper source rock in south sags and reservoir inside source rock in north sag, there was a small amount of hydrocarbon migration in middle Minghuazhen Formation, mass hydrocarbon migration in late Minghuazhen Formation (2 Ma ago). At present, hydrocarbon distribution in south sags does not match the simulation results, which indicates greater potential for exploration. The geochemical index of crude oil show that in the enrichment area of reservoir upper source rock, hydrocarbon migration was along faults strike, to the tectonic high position and sandstone on both sides of fault plane when the source fault stretched into the Sag center. For source faults parallel to the Sag center, hydrocarbon migration was along the faults tendency to the tectonic high position. In the enrichment area of reservoir inside source rock, hydrocarbon migration was along sandstone to the tectonic high position.
2013, 38(1): 181-187.
doi: 10.3799/dqkx.2013.018
Abstract:
The rare earth element (REE) compositions of the "Wushan Loess" are studied in order to encipher information on the genesis of the "Wushan Loess". The REE patterns, concentrations and indices are used for the discussion. The results show that REE compositions of the "Wushan Loess" are quite different from those of the modern river sediments and similar to those of the Loess Plateau and the "Xiashu Loess" in the middle and lower Yangtze reaches. REE distribution patterns are similar to those of the typical eolian deposits. The index (PI) calculated by source discriminant function is similar to those of the eolian deposits, indicating the eolian origin. The average REE content (216.39×10-6) is significantly higher to the average rate of the earth crust (178.0×10-6), two samples from the Loess Plateau (178.22×10-6), and fairly close to the average rate of the samples from the Xiashu loess in the middle and lower Yangtze reaches (207.7×10-6). The light rare earth element (LREE) are relatively enriched, while the heavy rear earth element (HREE) are slightly missing. The ratios of LREE and HREE is 8.62. The element Eu negative anomaly is obvious; while the element Ce anomaly is not obvious. It indicates that "Wushan" loess has suffered more intense weathering than the Loess Plateau. The "Wushan Loess" formed under the same weathering conditions as the "Xiashu Loess".
The rare earth element (REE) compositions of the "Wushan Loess" are studied in order to encipher information on the genesis of the "Wushan Loess". The REE patterns, concentrations and indices are used for the discussion. The results show that REE compositions of the "Wushan Loess" are quite different from those of the modern river sediments and similar to those of the Loess Plateau and the "Xiashu Loess" in the middle and lower Yangtze reaches. REE distribution patterns are similar to those of the typical eolian deposits. The index (PI) calculated by source discriminant function is similar to those of the eolian deposits, indicating the eolian origin. The average REE content (216.39×10-6) is significantly higher to the average rate of the earth crust (178.0×10-6), two samples from the Loess Plateau (178.22×10-6), and fairly close to the average rate of the samples from the Xiashu loess in the middle and lower Yangtze reaches (207.7×10-6). The light rare earth element (LREE) are relatively enriched, while the heavy rear earth element (HREE) are slightly missing. The ratios of LREE and HREE is 8.62. The element Eu negative anomaly is obvious; while the element Ce anomaly is not obvious. It indicates that "Wushan" loess has suffered more intense weathering than the Loess Plateau. The "Wushan Loess" formed under the same weathering conditions as the "Xiashu Loess".
2013, 38(1): 188-194.
doi: 10.3799/dqkx.2013.019
Abstract:
The dips of slices' force were determined by numerical simulation method by taking Monkey Stone landslide the study subject in this paper. The differences between the dips calculated by numerical simulation and those determined by the semi-precise slice method including the transfer coefficient method, Rohre law, the U.S. Army Corps of Engineers, simplified method and practical recursive method were analyzed. The effect of assumption of the slices' force dips based on semi-accurate slice method on the accuracy of landslide stability coefficient was discussed, and the results calculated by accurate slice method were compared with those calculated by numerical simulation. The study proves the accuracy and applicability of those current major semi-precision slice methods.
The dips of slices' force were determined by numerical simulation method by taking Monkey Stone landslide the study subject in this paper. The differences between the dips calculated by numerical simulation and those determined by the semi-precise slice method including the transfer coefficient method, Rohre law, the U.S. Army Corps of Engineers, simplified method and practical recursive method were analyzed. The effect of assumption of the slices' force dips based on semi-accurate slice method on the accuracy of landslide stability coefficient was discussed, and the results calculated by accurate slice method were compared with those calculated by numerical simulation. The study proves the accuracy and applicability of those current major semi-precision slice methods.
2013, 38(1): 195-200.
doi: 10.3799/dqkx.2013.020
Abstract:
An energy-balanced unequal clustering algorithm is proposed to solve the "hotspot" problem caused by long ribbon topology of mine roadway, in which the cluster heads close to the sink which has heavy burden leading to failure. A new threshold formula is constructed to elect the candidate cluster heads. Candidate cluster heads determine the cluster heads by certain campaign radius. After a reasonable partition, the clusters closer to the sink node have fewer nodes than those farther away from the sink node to balance the energy consumption; the hybrid communication mode within the cluster is adopted for the load balancing; for the data-forwarding between the cluster heads, the lowest energy consumption mechanism is proposed to select the next hop. Simulation results show that this protocol can balance energy consumption effectively to extend the network life cycle.
An energy-balanced unequal clustering algorithm is proposed to solve the "hotspot" problem caused by long ribbon topology of mine roadway, in which the cluster heads close to the sink which has heavy burden leading to failure. A new threshold formula is constructed to elect the candidate cluster heads. Candidate cluster heads determine the cluster heads by certain campaign radius. After a reasonable partition, the clusters closer to the sink node have fewer nodes than those farther away from the sink node to balance the energy consumption; the hybrid communication mode within the cluster is adopted for the load balancing; for the data-forwarding between the cluster heads, the lowest energy consumption mechanism is proposed to select the next hop. Simulation results show that this protocol can balance energy consumption effectively to extend the network life cycle.
2013, 38(1): 201-210.
doi: 10.3799/dqkx.2013.021
Abstract:
In order to investigate the spatial distribution and its environmental significance of nitrate (NO3-) and ammonium (NH4+) in snowpack of glaciers in the Chinese Tianshan Mountains, the snow samples were collected at the accumulation zone on five typical glaciers from west to east: Glacier No. 72 at Qingbingtan of Tomur Peak (QG72), Glacier No. 51 at Haxilegen of Kuytun River (HG51), Urumqi Glacier No. 1 (UG1), Glacier No. 4 at Sigong River of Bogda Peak (SG4), and Miaoergou Flat-topped Glacier (MG) during 2004-2009. It is found that the concentration order of NO3- in snowpack is HG51 < UG1 < MG < QG72 < SG4, and the concentration order of NH4+ is QG72 < HG51 < MG < UG1 < SG4. The NOAA HYSPLIT air trajectory model and local environmental data demonstrate that the spatial distribution of nitrogen-containing ions is influenced by the long-distance pollution and atmospheric dust, the local anthropogenic output including industry and agriculture, as well as the sampling conditions.
In order to investigate the spatial distribution and its environmental significance of nitrate (NO3-) and ammonium (NH4+) in snowpack of glaciers in the Chinese Tianshan Mountains, the snow samples were collected at the accumulation zone on five typical glaciers from west to east: Glacier No. 72 at Qingbingtan of Tomur Peak (QG72), Glacier No. 51 at Haxilegen of Kuytun River (HG51), Urumqi Glacier No. 1 (UG1), Glacier No. 4 at Sigong River of Bogda Peak (SG4), and Miaoergou Flat-topped Glacier (MG) during 2004-2009. It is found that the concentration order of NO3- in snowpack is HG51 < UG1 < MG < QG72 < SG4, and the concentration order of NH4+ is QG72 < HG51 < MG < UG1 < SG4. The NOAA HYSPLIT air trajectory model and local environmental data demonstrate that the spatial distribution of nitrogen-containing ions is influenced by the long-distance pollution and atmospheric dust, the local anthropogenic output including industry and agriculture, as well as the sampling conditions.
