Kinematics and Ar/Ar geochronology of the Gaoligong and Chongshan shear systems, western Yunnan, China: Implications for early Oligocene tectonic extrusion of SE Asia

The Gaoligong and Chongshan shear systems (GLSS and CSSS) in western Yunnan, China, have similar tectonic significance to the Ailaoshan–Red River shear system (ASRRSS) during the Cenozoic tectonic development of the southeastern Tibetan syntaxis. To better understand their kinematics and the Cenozoic tectonic evolution of SE Asia, this paper presents new kinematic and ⁴⁰Ar/³⁹Ar geochronological data for these shear systems. All the structural and microstructural evidence indicate that the GLSS is a dextral strike-slip shear system while the CSSS is a sinistral strike-slip shear system, and both were developed under amphibolite- to greenschist-grade conditions. The ⁴⁰Ar/³⁹Ar dating of synkinematic minerals revealed that the strike-slip shearing on the GLSS and CSSS at least began at  32 Ma, possibly coeval with the onset of other major shear systems in SE Asia. The late-stage shearing on the GLSS and CSSS is dated at  27–29 Ma by the biotite ⁴⁰Ar/³⁹Ar ages, consistent with that of the Wang Chao shear zone (WCSZ), but  10 Ma earlier than that of the ASRRSS. The dextral Gaoligong shear zone within the GLSS may have separated the India plate from the Indochina Block during early Oligocene. Combined with other data in western Yunnan, we propose that the Baoshan/Southern Indochina Block escaped faster southeastward along the CSSS to the east and the GLSS to the west than the Northern Indochina Block along the ASRRSS, accompanying with the obliquely northward motion of the India plate during early Oligocene (28–36 Ma). During 28–17 Ma, the Northern Indochina Block was rotationally extruded along the ASRRSS relative to the South China Block as a result of continuously impinging of the India plate.     

Factors Influencing Diurnal Variations of Cloud and Precipitation in the Yushu Area of the Tibetan Plateau

Using the cloud radar, ground observations, and ECMWF Reanalysis v5 (ERA5) data, we investigate the factors in-fluencing nighttime precipitation during summer i...     

西藏南部加不拉组问题的讨论及隆子地区下侏罗统的发现

1974年,中国科学院青藏高原综合科学考察队的活动是在批林批孔运动中进行的。其考察范围主要在雅鲁藏布江中下游一带。     

河北阳原新生代玄武岩中两类辉石岩包体的矿物学和地球化学特征

位于大兴安岭-太行山重力梯度带西侧的阳原新生代玄武岩中含有大量橄榄岩和辉石岩包体。辉石岩包体含有绿色的Cr辉石岩和黑色的Al辉石岩包体两种类型,均为二辉岩,且多数样品中单斜辉石含量高于斜方辉石。岩石结构和主微量元素组成说明阳原辉石岩是高压堆晶体。其EMI型Sr-Nd同位素特征,明显不同于寄主玄武岩,暗示两者没有成因联系,而可能代表古老岩浆事件的产物。综合文献资料发现重力梯度带西侧的辉石岩包体大多具有富集同位素特征,而东侧的样品以亏损同位素组成为主。这种空间上的成分差异暗示重力梯度带分隔两个不同的地幔域,也可能与重力梯度带两侧岩石圈地幔形成时代不同有关。     

Fractionation of platinum group elements in upper mantle: Evidence from peridotite xenoliths from Wangqing

The peridotite xenoliths from Wangqing display a downward-concave PGE pattern with Pt at maximum due to Pt-Pd fractionation, which is different from the flat or negatively sloped patterns commonly observed for worldwide peridotite xenoliths and massifs. Taking into account the difference in partition coefficients of Pt and Pd between alloy and sulfide melt, it is suggested that some of the Wangqing peridotites must have been equilibrated with a melt in which alloy and sulfide coexisted. Segregation of Pt-rich alloy from Pd-sulfide melts due to density contrast and extraction of residual melts without sulfide saturation resulted in the fractionation of Pt from Pd. Project supported by the Ministry of Human Affairs and a part of an international collaboration program between the Chinese Academy of Sciences and Centre National de Recherche Scientifique (CNRS, France), and Australian Institute of Nuclear Sciences and Engineering (AINSE) grant to SJR.     

PREDICTION OF IMPACT OF THE THREE GORGES PROJECT ON ESTUARY BEACH OF THE YANGTZE RIVER

ＰＲＥＤＩＣＴＩＯＮＯＦＩＭＰＡＣＴＯＦＴＨＥＴＨＲＥＥＧＯＲＧＥＳＰＲＯＪＥＣＴＯＮＥＳＴＵＡＲＹＢＥＡＣＨＯＦＴＨＥＹＡＮＧＴＺＥＲＩＶＥＲＷｅｉｂｉｎｇＦＥＮＧ１ＹｉｇａｎｇＷＡＮＧ２ａｎｄＸｉｕｃｈｅｎｇＺＨＯＮＧ３ＡＢＳＴＲＡＣＴＡｌｔｈｏ...     

Chemostratigraphy of Flood Basalts in the Garze-Litang Region and Zongza Block: Implications for Western Extension of the Emeishan Large Igneous Province, SW China

The Late Permian Emeishan Large Igneous Province (ELIP) is commonly regarded as being located in the western part of the Yangtze craton, SW China, with an asymmetrical shape and a small area. This area, however, is just a maximum estimation because some parts of the ELIP were not recognized or dismembered and destroyed during the Triassic to Cenozoic tectonism. In this paper, the chemostratigraphical data of the Zongza block, the Garze-Litang belt and the Songpan-Garze block suggest that the Late Permian basalts in these areas have remarkable similarities to the ELIP basalts in petrography and geochemistry. Flood basalts in the Sanjiangkou area are composed of the lower part of the low-Ti (LT) tholeiite and the upper part of the high-Ti (HT) tholeiite, which is the same as the flood basalts on the western margin of the Yangtze craton. Flood basalts in the Zongza and Songpan-Garze areas, which are far from the Yangtze craton, consist of HT tholeiite only. This is the same as the flood basalts within the Y     

开垦对阿拉尔绿洲盐渍化荒漠土壤微生物群落的影响

近年来,以对天然荒漠进行开垦和耕作为标志的人类活动加速了中国西北干旱荒漠区的绿洲化进程,但这种土地利用方式的改变对干旱荒漠土壤微生物群落特征的影响及其机理尚不清楚。本研究利用qPCR和Illumina Miseq高通量扩增子测序技术对新疆阿拉尔绿洲开垦5年的棉花田（FS）和毗邻的天然荒漠（ND）的土壤细菌、古菌和真菌群落的生物量、多样性和群落结构进行了对比研究,揭示了驱动荒漠土壤微生物群落结构演变的主要因子。结果表明：（1）荒漠开垦为农田后,土壤细菌和真菌群落的生物量显著增加,而古菌群落生物量显著降低;细菌群落多样性明显提高,古菌群落的Shannon多样性指数显著降低,而真菌群落多样性没有显著变化。（2）盐渍化荒漠具有不同于其他干旱荒漠的土壤微生物群落结构,开垦显著改变了其土壤细菌、古菌和真菌的群落结构。其中,放线菌门、绿弯菌门、酸杆菌门、螺旋体菌门和浮霉菌门细菌、乌斯古菌门和芽枝霉门真菌的相对丰度显著增加,而盐纳古菌门的相对丰度则显著降低。（3）土壤电导率（EC）、总有机碳（TOC）、全氮（TN）、全磷（TP）是影响细菌群落结构的关键因子;古菌群落结构的主要影响因子为植被盖度、地上生物量和丰富度、TP和AP;EC是影响真菌群落结构的关键因子。综上所述,盐渍化荒漠开垦后由于其原生植被群落、化学肥料的使用和土壤属性（EC、TP和AP）的改变不同程度地改变了荒漠土壤微生物群落特征。相对而言,细菌群落对土地利用方式的改变响应最为敏感,而古菌和真菌群落的多样性和结构则保持相对稳定。