This study aims at identifying possible correlations between shapes, types of geophysical anomalies and borehole productivity according to geological and hydrogeotogical contexts. The methodology adopted was a two-pro...This study aims at identifying possible correlations between shapes, types of geophysical anomalies and borehole productivity according to geological and hydrogeotogical contexts. The methodology adopted was a two-pronged one--the first step sought to： （1） interpret the electrical resistivity values from horizontal profiling and vertical electrical sounding implemented in Seno province that preceded the drilling of 513 boreholes; （ii） interpret data from pumping tests carried out on boreholes having a discharge superior to 1 m3/h （＂positive borehole＂） by using Cooper-Jacob＇s method. In the second step, according to geology, authors tried to identify possible correlations between each of the qualitative geophysical parameters： ~shape of anomaly〉〉, tttype of anomaly〉〉 and ~〈type curve〉〉 on the one hand, and hydrogeological parameters such as discharge, alteration thickness, transmissivity and saturated level on the other. The results of this study have shown that the chances of having a positive borehole in Seno province are higher when the type of anomaly is TCC （80%）, shape of anomaly is ＂W＂ and when type curve is ＂H＂ （80%） for all geological formations. Granitic formations are those that record higher discharges while schists record high transmissivity values.展开更多
The basement rocks in the Kuluketage area are composed predominately of tonalite-trondhjemite-granodiorite rocks, and occured mainly in Xinger and Korla. U-Pb dating of TTG gneiss near Korla yielded a late Neoarchean ...The basement rocks in the Kuluketage area are composed predominately of tonalite-trondhjemite-granodiorite rocks, and occured mainly in Xinger and Korla. U-Pb dating of TTG gneiss near Korla yielded a late Neoarchean weighted mean 207Pb/206Pb age of 2.65 Ga, which is the oldest published age for the TTG rocks in the Kuluketage area and thus suggests that Archean terrane in the area was formed in the late Neoarchean. The Korla gneiss is much younger than the TTG rocks in the northern Altyn Tagh, eastern Tarim Craton, indicating that the oldest terrane of the Tarim Craton was exposed probably in the northern Altyn Tagh. Until late Neoarchean, the Tarim continent extends to the Kuluketage area and finally had generated a relatively large uniform Archean basement within the craton. Zircon Hf isotopic analyses of the TTG gneiss give low εHf(t) values (-5 to 1) with Paleoarchean to Mesoarchean two-stage model ages (TDM2) between 3.0 and 3.3 Ga, suggesting that the basement rocks in the northern Tarim Craton were derived dominately from partial melting of Paleoarchean to Mesoarchean juvenile crustal material. The Hf model ages, therefore, indicate that no continent crust older than 3.3 Ga existed in the Kuluketage area.展开更多
Zircon LA-ICP-MS U-Pb dating of the Jingju syenogranites in the southwestern part of Zhejiang Province shows that these rocks were crystallized in the Late Triassic at 215±2 Ma, rather than in the Cretaceous as p...Zircon LA-ICP-MS U-Pb dating of the Jingju syenogranites in the southwestern part of Zhejiang Province shows that these rocks were crystallized in the Late Triassic at 215±2 Ma, rather than in the Cretaceous as previously proposed. The Jingju sy- enogranites are characterized by relatively high K2O and FeO＊, and low MgO. They have high concentrations of large ion lithophile elements （LIL） and LREE, such as K, Th, La, and Ce, but are depleted in high field strength elements （HFSE） such as Nb, Ta, and Ti. Their 104Ga/A1 ratios and （Zr＋Nb＋Ce＋Y） contents are also high. These characteristics are similar to those of A-type granites. The syenogranites have high Isr （0.7179-0.7203）, low eNa（t） （from --14.2 to --13.2）, and relatively old T2DM ages, similar to those of the ancient metamorphic basement in the Cathaysia Block. It is suggested that the Jingju syenogranites were formed by partial melting of the Cathaysia basement rocks during tectonic extension. This identification of Indosinian A-type granite in Jingju has significant implications for understanding the early Mesozoic tectonic evolution of South China.展开更多
文摘This study aims at identifying possible correlations between shapes, types of geophysical anomalies and borehole productivity according to geological and hydrogeotogical contexts. The methodology adopted was a two-pronged one--the first step sought to： （1） interpret the electrical resistivity values from horizontal profiling and vertical electrical sounding implemented in Seno province that preceded the drilling of 513 boreholes; （ii） interpret data from pumping tests carried out on boreholes having a discharge superior to 1 m3/h （＂positive borehole＂） by using Cooper-Jacob＇s method. In the second step, according to geology, authors tried to identify possible correlations between each of the qualitative geophysical parameters： ~shape of anomaly〉〉, tttype of anomaly〉〉 and ~〈type curve〉〉 on the one hand, and hydrogeological parameters such as discharge, alteration thickness, transmissivity and saturated level on the other. The results of this study have shown that the chances of having a positive borehole in Seno province are higher when the type of anomaly is TCC （80%）, shape of anomaly is ＂W＂ and when type curve is ＂H＂ （80%） for all geological formations. Granitic formations are those that record higher discharges while schists record high transmissivity values.
基金supported by National Basic Research Program of China (Grant No. 2007CB411308)National Natural Science Foundation of China (Grant Nos. 40803009 and 40772130)CAS/SAFEA International Partnership Program for Creative Research Teams
文摘The basement rocks in the Kuluketage area are composed predominately of tonalite-trondhjemite-granodiorite rocks, and occured mainly in Xinger and Korla. U-Pb dating of TTG gneiss near Korla yielded a late Neoarchean weighted mean 207Pb/206Pb age of 2.65 Ga, which is the oldest published age for the TTG rocks in the Kuluketage area and thus suggests that Archean terrane in the area was formed in the late Neoarchean. The Korla gneiss is much younger than the TTG rocks in the northern Altyn Tagh, eastern Tarim Craton, indicating that the oldest terrane of the Tarim Craton was exposed probably in the northern Altyn Tagh. Until late Neoarchean, the Tarim continent extends to the Kuluketage area and finally had generated a relatively large uniform Archean basement within the craton. Zircon Hf isotopic analyses of the TTG gneiss give low εHf(t) values (-5 to 1) with Paleoarchean to Mesoarchean two-stage model ages (TDM2) between 3.0 and 3.3 Ga, suggesting that the basement rocks in the northern Tarim Craton were derived dominately from partial melting of Paleoarchean to Mesoarchean juvenile crustal material. The Hf model ages, therefore, indicate that no continent crust older than 3.3 Ga existed in the Kuluketage area.
基金supported by Ministry of Science and Technology of China (Grant No. 2007DFA21230)Natural Science Foundation of Hubei Province (Grant No. 2009CDA004)+2 种基金National Natural Science Foundation of China (Grant Nos. 40821061, 40334037)Ministry Education of China, State Administration of Foreign Expert Affairs of China (Grant No. B07039)Survey and Assessment of Geology and Mineral Resources (Grant No. B[2010]AMR01-17-05)
文摘Zircon LA-ICP-MS U-Pb dating of the Jingju syenogranites in the southwestern part of Zhejiang Province shows that these rocks were crystallized in the Late Triassic at 215±2 Ma, rather than in the Cretaceous as previously proposed. The Jingju sy- enogranites are characterized by relatively high K2O and FeO＊, and low MgO. They have high concentrations of large ion lithophile elements （LIL） and LREE, such as K, Th, La, and Ce, but are depleted in high field strength elements （HFSE） such as Nb, Ta, and Ti. Their 104Ga/A1 ratios and （Zr＋Nb＋Ce＋Y） contents are also high. These characteristics are similar to those of A-type granites. The syenogranites have high Isr （0.7179-0.7203）, low eNa（t） （from --14.2 to --13.2）, and relatively old T2DM ages, similar to those of the ancient metamorphic basement in the Cathaysia Block. It is suggested that the Jingju syenogranites were formed by partial melting of the Cathaysia basement rocks during tectonic extension. This identification of Indosinian A-type granite in Jingju has significant implications for understanding the early Mesozoic tectonic evolution of South China.
