The Cenozoic evolution history of Guizhou Province, which is located on the southeastern flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widesprea...The Cenozoic evolution history of Guizhou Province, which is located on the southeastern flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widespread on the Yunnan-Guizhou Plateau may bear critical information about their evolution history. This work firstly determined the ages of four red weathering crusts in eastern, central and northern Guizhou. The material used in fission track dating is well-crystallized quartz occurring in many in-situ weathering crusts of carbonate rocks. The results showed that the fission track ages of quartz vary over a wide range from 1 to 25 Ma in the four profiles, significantly younger than the ages of the Triassic and Cambrian parent rocks. In combination with the evolution history of the regional geology during the period from 25 to 1 Ma, the ages of quartz can exclude the possibility that the origin of quartz has nothing to do with primary clastic minerals in parent rocks, authigenesis during diagenesis and hydrothermal precipitation or roplacement by volcanic activities. It is deduced that the well-crystallized quartz was precipitated from Si-rich weathering fluids during the weathering process of carbonate rocks. The recorded ages of quartz from the four profiles are consistent with the episodes of the planation surfaces on the Qinghai-Tibet Plateau, the forming stages of red soil in the tropics of South China, the tectonically stable periods in Guizhou, and the ages of weathering in other parts of the world during the Cenozoic era. That is to say, the ages of authigenic quartz dated by the fission track method are well feasible and credible.展开更多
Owing to the low contents of their acid-insoluble components, carbonate rocks tend to decrease sharply in volume in association with the formation of weathering crust. The formation of a 1 m-thick weathering crust wou...Owing to the low contents of their acid-insoluble components, carbonate rocks tend to decrease sharply in volume in association with the formation of weathering crust. The formation of a 1 m-thick weathering crust would usually consume more than ten meters to several tens of meters of thickness of parent rocks. The knowledge of how to identify the homogeneity of parent rocks is essential to understand the formation mechanism of weathering crust in karst regions, especially that of thick-layered red weathering crust. In this work the grain-size analyses have demonstrated that the three profiles studied are the residual weathering crust of carbonate rocks and further showed that there objectively exists the heterogeneity of parent rocks in the three studied weathering crusts. The heterogeneity of parent rocks can also be reflected m geochemical parameters of major elements, just as the characteristics of frequency plot of grain-size distribution. Conservative trace element ratios Zr/Hf and Nb/Ta are proven to be unsuitable for tracing the heterogeneity of parent rocks of weathering crust, but its geochemical mechanism is unclear. The authors strongly suggest in this paper that the identification of the homogeneity of parent rocks of weathering crust in karst regions is of prime necessity.展开更多
On the basis of mineralogical, geochemical and micro\|textural studies of the typical sections of the red weathering crust of carbonate rocks in the subtropical karst areas of Guizhou Province and Guangxi Autonomous R...On the basis of mineralogical, geochemical and micro\|textural studies of the typical sections of the red weathering crust of carbonate rocks in the subtropical karst areas of Guizhou Province and Guangxi Autonomous Region, we have found, either on a microscopic or on a macroscopical scale and in different positions of the sections, the most direct and most important mineralogical and micro\|textural evidence for the development of metasomatism in the process of weathering\|pedogenesis of numerous carbonate rocks. This paper also has expounded for the first time and systematically the mechanism of metasomatism involved in the process of weathering\|pedogenesis of carbonate rocks and proposed the sequence of mineral metasomatic evolution in the process of weathering\|pedogenesis of carbonate rocks.展开更多
The genetic analysis of the deep-buried reservoirs of the Lower Paleozoiccarbonate rocks in the Tarim basin is a difficult task involving many factors. Firstly, the objectof study is carbonate rocks, which have underg...The genetic analysis of the deep-buried reservoirs of the Lower Paleozoiccarbonate rocks in the Tarim basin is a difficult task involving many factors. Firstly, the objectof study is carbonate rocks, which have undergone a long term of modification. Secondly, the rocksare deeply buried with depths of 3800-7000 m in the Tarim basin. The primary reservoir propertiesformed in the deposition have been strongly modified during the deep burial process. Concurrently,the different burial depths in different areas result in diversities of burial temperature,pressure, underground water, hydrochemistry and various physicochemical changes, which further leadto differences in the diagenetic type, diagenetic property, diagenetic degree and their impacts onthe reservoir properties. The Lower Paleozoic Cambrian and Ordovician carbonate reservoirs in theTarim basin can be grouped into four types, i.e., paleo-weathered-crust reservoirs, reef reservoirs,buried karst reservoirs and dolomite reservoirs. This paper presents a detailed discussion on thevertical and horizontal distribution characteristics, morphological division, reservoir propertiesand the efficiency in accumulating hydrocarbons of the paleo-weathered-crust type. Furthermore, itsgenesis is also analyzed. We proposed that the composition of the carbonate rocks, the tectonicmovement with associated fractures and fissures, the paleomorphology and paleoclimate, the sea levelfluctuation, and the protection of the pores and fissures by the deep burial diagenesis and burialdissolution are the main factors controlling the formation of the paleo-weathered-crust reservoirs.We also consider that the petroleum exploration of the Lower Paleozoic carbonate rocks should befocused on the pale-weathered-crust reservoirs.展开更多
THE Pingba soil profile developed on the bedrock Triassic dolomitite and morphologically located in uplandin karst terrain in Central Guizhou, China was proven to be in-situ dolomitite weathering pedogeneticproduct. C...THE Pingba soil profile developed on the bedrock Triassic dolomitite and morphologically located in uplandin karst terrain in Central Guizhou, China was proven to be in-situ dolomitite weathering pedogeneticproduct. Continuous sampling method was used for taking samples from man-made excavated pit fromthe Pingba profile. REE for samples was measured on ELEMENT ICP-MS in the Institute of Geochemistry, CAS. The standard reference samples GSR-6 and GSS-1,4,7 were used to monitor the precisionof REE measurement. The measurement error was less than ≤10%. For PB-T1 sample, the coefficientof variation (CV) of three analytical run precision is: La, Ce, Pr, Nd, Ho, Er≤10%; Sm, Eu, Dy,Tm≤15%; Y, Lu, Gd, Tb≤20%.展开更多
基金This work was granted by the National Natural Science Foundation of China(Nos.40371012 and 49833002).
文摘The Cenozoic evolution history of Guizhou Province, which is located on the southeastern flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widespread on the Yunnan-Guizhou Plateau may bear critical information about their evolution history. This work firstly determined the ages of four red weathering crusts in eastern, central and northern Guizhou. The material used in fission track dating is well-crystallized quartz occurring in many in-situ weathering crusts of carbonate rocks. The results showed that the fission track ages of quartz vary over a wide range from 1 to 25 Ma in the four profiles, significantly younger than the ages of the Triassic and Cambrian parent rocks. In combination with the evolution history of the regional geology during the period from 25 to 1 Ma, the ages of quartz can exclude the possibility that the origin of quartz has nothing to do with primary clastic minerals in parent rocks, authigenesis during diagenesis and hydrothermal precipitation or roplacement by volcanic activities. It is deduced that the well-crystallized quartz was precipitated from Si-rich weathering fluids during the weathering process of carbonate rocks. The recorded ages of quartz from the four profiles are consistent with the episodes of the planation surfaces on the Qinghai-Tibet Plateau, the forming stages of red soil in the tropics of South China, the tectonically stable periods in Guizhou, and the ages of weathering in other parts of the world during the Cenozoic era. That is to say, the ages of authigenic quartz dated by the fission track method are well feasible and credible.
基金This work was jointly supported by the Knowledge-Innovation Project of the Institute of Geochemistry,the“Westerm Light”Program sponsored by the Chinese Academy of Sciencesthe National Natural Science Foundation of China grants 49833002,40273015 and 40371012.
文摘Owing to the low contents of their acid-insoluble components, carbonate rocks tend to decrease sharply in volume in association with the formation of weathering crust. The formation of a 1 m-thick weathering crust would usually consume more than ten meters to several tens of meters of thickness of parent rocks. The knowledge of how to identify the homogeneity of parent rocks is essential to understand the formation mechanism of weathering crust in karst regions, especially that of thick-layered red weathering crust. In this work the grain-size analyses have demonstrated that the three profiles studied are the residual weathering crust of carbonate rocks and further showed that there objectively exists the heterogeneity of parent rocks in the three studied weathering crusts. The heterogeneity of parent rocks can also be reflected m geochemical parameters of major elements, just as the characteristics of frequency plot of grain-size distribution. Conservative trace element ratios Zr/Hf and Nb/Ta are proven to be unsuitable for tracing the heterogeneity of parent rocks of weathering crust, but its geochemical mechanism is unclear. The authors strongly suggest in this paper that the identification of the homogeneity of parent rocks of weathering crust in karst regions is of prime necessity.
基金This research project was financially supported by both National Natural Science Foundation of China (GrantNo .4 980 0 0 3)andCross Century Qualified Personnel Program of Guizhou Province
文摘On the basis of mineralogical, geochemical and micro\|textural studies of the typical sections of the red weathering crust of carbonate rocks in the subtropical karst areas of Guizhou Province and Guangxi Autonomous Region, we have found, either on a microscopic or on a macroscopical scale and in different positions of the sections, the most direct and most important mineralogical and micro\|textural evidence for the development of metasomatism in the process of weathering\|pedogenesis of numerous carbonate rocks. This paper also has expounded for the first time and systematically the mechanism of metasomatism involved in the process of weathering\|pedogenesis of carbonate rocks and proposed the sequence of mineral metasomatic evolution in the process of weathering\|pedogenesis of carbonate rocks.
文摘The genetic analysis of the deep-buried reservoirs of the Lower Paleozoiccarbonate rocks in the Tarim basin is a difficult task involving many factors. Firstly, the objectof study is carbonate rocks, which have undergone a long term of modification. Secondly, the rocksare deeply buried with depths of 3800-7000 m in the Tarim basin. The primary reservoir propertiesformed in the deposition have been strongly modified during the deep burial process. Concurrently,the different burial depths in different areas result in diversities of burial temperature,pressure, underground water, hydrochemistry and various physicochemical changes, which further leadto differences in the diagenetic type, diagenetic property, diagenetic degree and their impacts onthe reservoir properties. The Lower Paleozoic Cambrian and Ordovician carbonate reservoirs in theTarim basin can be grouped into four types, i.e., paleo-weathered-crust reservoirs, reef reservoirs,buried karst reservoirs and dolomite reservoirs. This paper presents a detailed discussion on thevertical and horizontal distribution characteristics, morphological division, reservoir propertiesand the efficiency in accumulating hydrocarbons of the paleo-weathered-crust type. Furthermore, itsgenesis is also analyzed. We proposed that the composition of the carbonate rocks, the tectonicmovement with associated fractures and fissures, the paleomorphology and paleoclimate, the sea levelfluctuation, and the protection of the pores and fissures by the deep burial diagenesis and burialdissolution are the main factors controlling the formation of the paleo-weathered-crust reservoirs.We also consider that the petroleum exploration of the Lower Paleozoic carbonate rocks should befocused on the pale-weathered-crust reservoirs.
文摘THE Pingba soil profile developed on the bedrock Triassic dolomitite and morphologically located in uplandin karst terrain in Central Guizhou, China was proven to be in-situ dolomitite weathering pedogeneticproduct. Continuous sampling method was used for taking samples from man-made excavated pit fromthe Pingba profile. REE for samples was measured on ELEMENT ICP-MS in the Institute of Geochemistry, CAS. The standard reference samples GSR-6 and GSS-1,4,7 were used to monitor the precisionof REE measurement. The measurement error was less than ≤10%. For PB-T1 sample, the coefficientof variation (CV) of three analytical run precision is: La, Ce, Pr, Nd, Ho, Er≤10%; Sm, Eu, Dy,Tm≤15%; Y, Lu, Gd, Tb≤20%.
