Objective The Late Paleozoic Southern Tianshan Ocean is usually considered to be the last-closed ocean in the Tianshan Orogeny. However, there is still no consensus if this is indeed the case. Blueschist, eclogite an...Objective The Late Paleozoic Southern Tianshan Ocean is usually considered to be the last-closed ocean in the Tianshan Orogeny. However, there is still no consensus if this is indeed the case. Blueschist, eclogite and ophiolite are present in the Atbashi Range, Kyrgyzstan, which are believed to be the relics of the Southern Tianshan Ocean. New data obtained through Ar-Ar isotopic analysis in this research provide reliable chronological restrictions for this problem.展开更多
The dike swarm of lamprophyres at Pishan on the SW margin of the Tarimterrane is composed of ultra-potassic lamprophyres that have intruded into the Proterozoichornblende schists. ^(40)Ar/^(39)Ar dating data suggest t...The dike swarm of lamprophyres at Pishan on the SW margin of the Tarimterrane is composed of ultra-potassic lamprophyres that have intruded into the Proterozoichornblende schists. ^(40)Ar/^(39)Ar dating data suggest that the isochron ages for phlogopite andwhole rock separates of the lamprophyres are 231.7+-0.3 Ma and 228.5+-0.3 Ma, respectively.Geochemical data indicate that the dikes were derived from a subduction-related or metasomatizedmantle. During the Middle-Late Triassic the western Kunlun area entered the post-orogeny period, andthus the occurrence of the dike swarm in the study area may have been controlled by underplating.展开更多
The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lodegold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has beenargued that it was formed in the Mesozoic...The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lodegold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has beenargued that it was formed in the Mesozoic, related isotopic age data have not been reported inprevious studies. Based on detailed geological study, the authors have carried out isotopic datingon various metallogenic generations. The ore-forming process of the Dongchuang gold deposit consistsof four stages: coarse-grained pyrite-bearing quartz veins (stage I), fine-grained pyrite-quartzveinlets (stage II), multi-sulfides (stage III) and carbonate-quartz veinlets (stage IV). Ar-Ardating on mineral separates of stages I, II and III yields plateau ages of 142.9 +- 2.9 Ma, 132.2 +-2.6 Ma and 128.3 +- 6.2 Ma, respectively. Sericite separates from stage II assemblage also yield anAr-Ar isochron age of 132.6 +- 2.7 Ma, similar to the Ar-Ar plateau age. These results suggest thatthe Dongchuang gold deposit was mainly formed during 143-128 Ma, coinciding with the authors'geological observations and previous hypothesis. This ore formation is coeval with theregional-tectonic transition from collisional compression to extension, strongly showing that thedecompression-geothermal increase regime during compression-to-extension transition is the mostconducive geodynamic environment to orogenic-type gold mineralization.展开更多
The Xianghualing Sn-polymetallic orefield in Hunan Province, southern China, is a largesize tin orefield. Although numerous studies have been undertaken on this orefield, its genesis, mineralization age, and tectonic ...The Xianghualing Sn-polymetallic orefield in Hunan Province, southern China, is a largesize tin orefield. Although numerous studies have been undertaken on this orefield, its genesis, mineralization age, and tectonic setting are still controversial, mainly because of the lack of reliable geochronological data on tin mineralization. The ^40Ar^39Ar stepwise heating dating method was first employed on muscovite from different deposits in this orefield. The muscovite sample from the Xianghualing Sn-polymetallic deposit defines a plateau age of 154.4±1.1 Ma and an isochron age of 151.9±3.0 Ma; muscovite from the Xianghuapu W-polymetallic deposit yields a plateau age of 161.3±1.1 Ma and an isochron age of 160.0±3.2 Ma; muscovite from the Jianfengling greisen-type Sn-polymetallic deposit gives a plateau age of 158.7±1.2 Ma and an isochron age of 160.3±3.2 Ma. The tungsten-tin mineralization ages in the Xianghualing area are therefore restricted within 150-160 Ma. The tungstentin mineralization in Xianghualing occurred at the same time as the regional tin-tungsten mineralization including the Furong tin orefield, Shizhuyuan tungsten-tin polymetallic deposit and Yaogangxian tungsten-polymetallic deposit. Thus, the large-scale tungsten-tin metallogenesis in South China occurring at 160-150 Ma, probably is closely related to asthenospheric upwelling and crustmantle interaction under a geodynamic setting of crustal extension and lithosphere thinning during the transformation of tectonic regimes during the Mid-Late Jurassic.展开更多
Furong, Hunan, is a large tin orefield discovered in China in recent years, which is mainly of the skarn-greisen-chlorite type. On the basis of the geological characteristics of the orefield, 40Ar-39Ar dating was perf...Furong, Hunan, is a large tin orefield discovered in China in recent years, which is mainly of the skarn-greisen-chlorite type. On the basis of the geological characteristics of the orefield, 40Ar-39Ar dating was performed on muscovite from greisen-type tin ore and biotite from related amphibole-biotite granite, which yielded three sets of age data, i.e., a plateau age of 157.5±0.3 Ma and an isochron age of 156.9±3 Ma for amphibole-biotite granite; a plateau age of 156.1±0.4 Ma and an isochron age of 155.7±1.7 Ma for the Sanmen greisen-type tin ore; and a plateau age of 160.1±0.9 Ma and an isochron age of 157.5±1.5 Ma for the Taoxiwo greisen-type tin ore. The three sets of age data coincide well with each other. They not only accurately reflect the timing of rock and ore formation but also indicate close relations between granite and tin deposits. In addition, the plateau ages of all three sets suggest that no subsequent thermal perturbation event occurred after the formation of granite and tin deposits. The Furong tin orefield is a component part of the southern Hunan large tungsten-tin polymetallic deposit concentration area and also a representative deposit formed in the time interval of 160-135 Ma in four peaks of Mesozoic tungsten-tin mineralization in the South China region. They might still correspond to the middle and late stages of the major geodynamic transition from a N-S- to an E-W-direction in eastern China.展开更多
基金sponsored by the China Geological Survey(grants No.1212011120335 and 12120114006201)
文摘Objective The Late Paleozoic Southern Tianshan Ocean is usually considered to be the last-closed ocean in the Tianshan Orogeny. However, there is still no consensus if this is indeed the case. Blueschist, eclogite and ophiolite are present in the Atbashi Range, Kyrgyzstan, which are believed to be the relics of the Southern Tianshan Ocean. New data obtained through Ar-Ar isotopic analysis in this research provide reliable chronological restrictions for this problem.
文摘The dike swarm of lamprophyres at Pishan on the SW margin of the Tarimterrane is composed of ultra-potassic lamprophyres that have intruded into the Proterozoichornblende schists. ^(40)Ar/^(39)Ar dating data suggest that the isochron ages for phlogopite andwhole rock separates of the lamprophyres are 231.7+-0.3 Ma and 228.5+-0.3 Ma, respectively.Geochemical data indicate that the dikes were derived from a subduction-related or metasomatizedmantle. During the Middle-Late Triassic the western Kunlun area entered the post-orogeny period, andthus the occurrence of the dike swarm in the study area may have been controlled by underplating.
基金This study was financially supported by the National Sciencc Foundation of China(No.49972035).
文摘The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lodegold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has beenargued that it was formed in the Mesozoic, related isotopic age data have not been reported inprevious studies. Based on detailed geological study, the authors have carried out isotopic datingon various metallogenic generations. The ore-forming process of the Dongchuang gold deposit consistsof four stages: coarse-grained pyrite-bearing quartz veins (stage I), fine-grained pyrite-quartzveinlets (stage II), multi-sulfides (stage III) and carbonate-quartz veinlets (stage IV). Ar-Ardating on mineral separates of stages I, II and III yields plateau ages of 142.9 +- 2.9 Ma, 132.2 +-2.6 Ma and 128.3 +- 6.2 Ma, respectively. Sericite separates from stage II assemblage also yield anAr-Ar isochron age of 132.6 +- 2.7 Ma, similar to the Ar-Ar plateau age. These results suggest thatthe Dongchuang gold deposit was mainly formed during 143-128 Ma, coinciding with the authors'geological observations and previous hypothesis. This ore formation is coeval with theregional-tectonic transition from collisional compression to extension, strongly showing that thedecompression-geothermal increase regime during compression-to-extension transition is the mostconducive geodynamic environment to orogenic-type gold mineralization.
基金the Innovative Project of the Chinese Academy of Sciences （Grant No. KZCX3-SW-125） National Natural Science Foundation of China （Grant No. 40472053 , No. 40673021）.
文摘The Xianghualing Sn-polymetallic orefield in Hunan Province, southern China, is a largesize tin orefield. Although numerous studies have been undertaken on this orefield, its genesis, mineralization age, and tectonic setting are still controversial, mainly because of the lack of reliable geochronological data on tin mineralization. The ^40Ar^39Ar stepwise heating dating method was first employed on muscovite from different deposits in this orefield. The muscovite sample from the Xianghualing Sn-polymetallic deposit defines a plateau age of 154.4±1.1 Ma and an isochron age of 151.9±3.0 Ma; muscovite from the Xianghuapu W-polymetallic deposit yields a plateau age of 161.3±1.1 Ma and an isochron age of 160.0±3.2 Ma; muscovite from the Jianfengling greisen-type Sn-polymetallic deposit gives a plateau age of 158.7±1.2 Ma and an isochron age of 160.3±3.2 Ma. The tungsten-tin mineralization ages in the Xianghualing area are therefore restricted within 150-160 Ma. The tungstentin mineralization in Xianghualing occurred at the same time as the regional tin-tungsten mineralization including the Furong tin orefield, Shizhuyuan tungsten-tin polymetallic deposit and Yaogangxian tungsten-polymetallic deposit. Thus, the large-scale tungsten-tin metallogenesis in South China occurring at 160-150 Ma, probably is closely related to asthenospheric upwelling and crustmantle interaction under a geodynamic setting of crustal extension and lithosphere thinning during the transformation of tectonic regimes during the Mid-Late Jurassic.
文摘Furong, Hunan, is a large tin orefield discovered in China in recent years, which is mainly of the skarn-greisen-chlorite type. On the basis of the geological characteristics of the orefield, 40Ar-39Ar dating was performed on muscovite from greisen-type tin ore and biotite from related amphibole-biotite granite, which yielded three sets of age data, i.e., a plateau age of 157.5±0.3 Ma and an isochron age of 156.9±3 Ma for amphibole-biotite granite; a plateau age of 156.1±0.4 Ma and an isochron age of 155.7±1.7 Ma for the Sanmen greisen-type tin ore; and a plateau age of 160.1±0.9 Ma and an isochron age of 157.5±1.5 Ma for the Taoxiwo greisen-type tin ore. The three sets of age data coincide well with each other. They not only accurately reflect the timing of rock and ore formation but also indicate close relations between granite and tin deposits. In addition, the plateau ages of all three sets suggest that no subsequent thermal perturbation event occurred after the formation of granite and tin deposits. The Furong tin orefield is a component part of the southern Hunan large tungsten-tin polymetallic deposit concentration area and also a representative deposit formed in the time interval of 160-135 Ma in four peaks of Mesozoic tungsten-tin mineralization in the South China region. They might still correspond to the middle and late stages of the major geodynamic transition from a N-S- to an E-W-direction in eastern China.
