Hydrogeochemical and isotopic study of groundwater in the Habor Lake Basin of the Ordos Plateau,NW China

Hydrogeochemistry and isotopes were used to understand the origin and geochemical evolution in the Habor Lake Basin, northwestern China. Groundwater samples were taken, and the isotopic compositions δD, δ¹⁸O and major ions were analyzed. The groundwater can be divided into three types: the Quaternary groundwater, the shallow Cretaceous groundwater and the deep Cretaceous groundwater. The groundwater chemistry is mainly controlled by the feldspar weathering and dolomite weathering, the dissolution of Glauber’s salt, and cation exchange. Chemistry of lake water is mainly controlled by evaporation and precipitation. The stable isotopes of oxygen and hydrogen in groundwater cluster along the local meteoric water line, indicating that groundwater is of meteoric origin. Comparing with shallow groundwater, deep groundwater is depleted in heavy isotopes indicating that deep groundwater was recharged during late Pleistocene and Holocene, during which the climate was more wetter and colder than today.     

上扬子陆块西南缘早—中元古代造山运动的地质记录

早—中元古代,上扬子陆块西南缘发育有河口群—大红山群、东川群、昆阳群—会理群为代表的3套浅变质火山-沉积岩系.已有的岩石学、地球化学、年代同位素数据指示了其大地构造格架及其演化史.在早—中元古代地层所夹的火山岩中,获得了4组SHRIMP U-Pb岩浆锆石年龄:1800～1600Ma、1600～1300Ma、1300～1100Ma、1100～1000Ma.结合沉积相、常量、微量、稀土元素地球化学分析,证明了上扬子陆块西南缘在早—中元古代也相应历经了4个演化阶段.1800～1600Ma,在大红山地区、河口地区、东川汤丹地区形成近东西向的裂谷盆地.1600～1300Ma,在东川因民地区表现为—被动陆缘下的伸张环境.1300～1100Ma,在菜籽园—麻塘地区为板内裂谷-洋盆,老武山地区为裂谷盆地.1100～1000Ma阶段,菜籽园-麻塘裂谷-洋盆向北俯冲或向北向南双向俯冲,在北边的天宝山地区和南边的富良棚地区形成火山岛弧,同时在扬子西缘也出现了1.0Ga左右(1007±14～1014±8 Ma)的同造山或同碰撞型花岗岩,表明此时康滇地区已经拼贴到一起,并与整个上扬子陆块Rodinia超大陆形成同步.     

Case history of controlling a landslide at Panluo open-pit mine in China

Controlling of landsides safely and economically is a great challenge to mine operators because landslides are major geological problems especially in open-pit mines. In this paper, a case history at Panluo open-pit mine is presented in detail to share the experiences and lessons with mine operators. Panluo open-pit mine is located in the southwestern Fujian province of China. It is the largest open-pit iron mine in the Fujian province and was planned in 1965 and is in full operation from 1978. In July 1990, an earthquake of magnitude 5.3 in Taiwan Strait and big rainstorms impacted the mine slope, causing tension cracks and rather large-scale failures, and forming a U-shaped landslide. Total potential volume was estimated to be up to 1.0 × 10⁶ m³. This directly threatened the mine production. In order to protect the mine production and the dwellers’ safety around, a dynamic comprehensive method was implemented including geotechnical investigations, in-situ testing and monitoring, stability analysis, and many mitigation and preventive measures. These measures slowed down the development and further occurrence of the landslide. The results showed that the landslides were still active, it was slowed with the control measures and moved rapidly with rainfall and mining down. However, no catastrophic accidents occurred and the pit mining was continued till it was closed at the elevation of 887 m in 2000. As a successful case of landslide control at an open-pit mine for 10 years, this paper reports the controlling measures in details. These experiences of landslide control may be beneficial to other similar mines for landslide control.     

Micro-XANES mapping of sulphur and its association with magnesium and phosphorus in the shell of the brachiopod, Terebratulina retusa

Biominerals are natural composite materials comprising organic and inorganic components. Detailed knowledge of the nature and distribution of both components is a crucial requirement in order to advance our understanding of biomineral formation, their material properties and preservation potential as well as the interpretation of environmental data. Detailed chemical data are essential for our understanding of the nature and distribution of such components. Micro-XANES mapping at the sulphur K-edge reveals that, in the brachiopod Terebratulina retusa, the sulphate concentration is higher in the outer (primary) layer than in the calcite fibres of the secondary layer. This is co-incident with a higher magnesium concentration. In contrast, the sheaths surrounding the calcite fibres contain sulphur as thiol, confirming the presence of protein while, the sulphur within the fibres themselves, occurs as sulphate. Micro-XANES analysis of the insoluble organic extract from T. retusa indicates the presence of organic sulphate while Micro-Raman spectroscopy confirms that structurally substituted sulphate (SSS) is also present although semi-quantitative Raman spectroscopy carried out in this spectral region (wavenumbers 900–1200) indicates that the sulphate present is at the threshold of detection by Raman spectroscopy. The distribution of phosphorus in the shell of T. retusa correlates well with that of protein indicating the presence of phosphorylated proteins in the periostracum, the sheaths surrounding the calcite fibres and the interface between the primary and secondary layer.     

Discovery of Pyrrhotite-Chalcopyrite-Bearing Amphibole Megacrysts in Tongling Area, Anhui Province

Some pyrrhotite-chalcopyrite-bearing amphibole megacrysts (including pyroxene megacrysts) were discovered in Mesozoic augite diorite-porphyrite at Caoshan in Tongling area, Anhui Province. The amphibole megacrysts, belonging mainly to pargasite and magnesiohastingsite, are characteristic of the amphibole composition derived from mantle and crystallized in lower crust. In general, the aggregates of pyrrhotite-chalcopyrite take the shapes of cylinder and sphere. Three occurrences have been recognized in the amphibole megacrysts: parallel linear, bunchy and scattered. The unique cylinder-like shape of the aggregates and remarkable Ni-poor sulfides in Caoshan are distinctively different from the spherical Ni-rich sulfides in pyroxene megacrysts and any other kinds of megacrysts. In terms of composition, the amphibole megacrysts and their sulfides in Caoshan are similar to those in the pyroxenite xenoliths in Qilin, Guangdong Province. In terms of origin, the pyrrhotite-chalcopyrites as exsolution products resulted from the subsolidus re-equilibration of sulfide solid solution within amphibole megacrysts.amphibole megacrysts were first discovered inside and outside China. This discovery is important for the study of regional magma evolution and its associated mineralizations and ore sources as well.     

川西与滇东震旦系—寒武系边界层遗迹化石比较及地质意义的探讨

本文通过对我国震旦系-寒武系边界层中厚度较大、化石丰富、生物演变序列清楚的川西和滇东地区遗迹化石的研究,并比较其异同点,从而阐明遗迹化石对寒武系底界的划分及恢复古环境方面的意义。     

Correction of common lead in U-Pb analyses that do not report 204 Pb

During the Early-Middle Proterozoic era, three major lithostratigraphic unit associations, namely Hekou-Dahongshan, Dongchuan, and Kunyang-Huili Groups, were established for the metamorphosed volcanic-sedimentary rocks exposed in the southwestern Yangtze Block (SWYB). The integration of petrology, geochemistry and geochronology constrains tectonic framework and evolution of the SWYB, in which four sets of SHRIMP U-Pb zircon ages were obtained from the volcanic rocks interbedded within the Middle Proterozoic successions: 1800–1600 Ma, 1600–1300 Ma, 1300–1100 Ma, and 1100–1000 Ma. Major and trace elemental analysis indicate that four key tectonic evolutionary stages, each coinciding with the above radiometric age set, of the SWYB during the Early-Middle Mesoproterozoic. The SWYB was characterized by an east-westerly trending rift in the Hekou, Dongshan, and Dongchuan areas, and separate basin-forming events during 1800–1600 Ma and 1600–1300 Ma, respectively. In the SWYB, an intracontinental rift basin and a rift basin occurred in the Caiziyuan-Matang and Laowushan areas, respectively in 1300–1100 Ma ago. During 1100–1000 Ma, the SWYB was characterized by the closure of the Caiziyuan-Matang rift-ocean basin, collision between the Huili Blocks and Kunyang Blocks, and presence of volcanic arcs in the Tianbaoshan and Fulingpen areas. Accordingly, the SWYB represents a new basin that records the relatively complete assembly process of the Rodina during the Early-Middle Mesoproterozoic era.     

大九湖泥炭地现代植物不同组分的δ18O特征及其古气候意义

最初学者利用泥炭植物同位素重建气候变化是参考树轮的研究方法,而树轮中不同组分的同位素对气候变化的响应不同。泥炭地植物不同组分的同位素对气候的响应是否也存在差异,需要进一步探讨和研究。此外,不同泥炭地植物δ¹⁸O的气候学解译存在一定的争议,这些解译的差异要求我们在利用泥炭δ¹⁸O重建古气候时需结合泥炭地现代过程的监测。文章以中国东部季风区的大九湖泥炭地为研究区域,测试研究区现代植被α纤维素与综纤维素的δ¹⁸O,对比两者的分布特征及其在时间序列上的相关性,进而探讨它们对气候因子的响应程度。结果表明：大九湖泥炭地植物δ¹⁸O分布较离散,平均值为25.09‰,α纤维素的δ¹⁸O比综纤维素δ¹⁸O偏正0.79‰~1.06‰,两种组分的δ¹⁸O在季节变化序列上没有明显的相关性。通过与区域气候因子的对比,我们发现温度是影响该地区植物δ¹⁸O变化的主要因素,而且植物α纤维素的δ¹⁸O比综纤维素的δ¹⁸O对温度响应更敏感,植物α纤维素更适用于作为研究古气候变化的载体,这一结果为中国东部季风内将泥炭地植物α纤维素的δ¹⁸O作为温度变化的代用指标提供了实验支持。

     

Geochemical characteristics of heavy metals in coastal sediments from the northern Beibu Gulf (SW China): the background levels and recent contamination

Four sediment cores and one hundred surface sediments were collected from the intertidal zone of the northern Beibu Gulf (SW China). In order to detect the intensity of metal contamination recently, the background levels were successfully established for Pb, Zn, Cd and Cr, based on the linear regression of deeper sediments (pre-industrial). Aluminum is a better geochemical normalizer than Fe and it is commonly used to describe the natural metal variability of the coastal sediments. The evident enrichment of Zn and Cd is recorded in the surface sediments of the eastern side of the Guangxi coast and the central part of the Qinzhou Bay, but it does not exceed the effects range-low values, due to a low percentage of fine-grained sediments in the region. Although the Pb and Cr concentrations are mainly of natural origin, 3 and 6% sites exceed the effects range-low values, respectively; indicating the potential for adverse ecological effects of metals on the benthic communities.     

Isotopic effect of runoff in the Yarlung Zangbo River

This paper mainly analyzed the isotopic effect of precipitation in the Yarlung Zangbo River.On the whole,the isotopic compositions of most water samples fall on the upper right of the global meteoric water line.According to δD and δ18O data of the samples,the precipitation equation is figured out as δD=8 δ18O+10,showing that they are derived from precipitation but have experienced intensive evaporation.With obvious region-continental effect(a continuous depletion in heavy isotopes in water bodies occurs with increasing distance from the coast),the water presents a reducing trend of δD and δ18O westwards and southwards.Altitudinal effect is evident here,occur-ring in both trunk stream and main branches of the Yarlung Zangbo River.The distribution of water isotopic compo-sitions is concerned with the movement of precipitation clouds from the Bay of Bengal and the Nujiang River and is affected by the topographic and climatic conditions of the Tibetan Plateau.