In situ Pb and bulk Sr isotope analysis of the Yinchanggou Pb-Zn deposit in Sichuan Province (SW China): Constraints on the origin and evolution of hydrothermal fluids

The Yinchanggou Pb-Zn deposit, located in southwestern Sichuan Province, western Yangtze Block, is stratigraphically controlled by late Ediacaran Dengying Formation and contains >0.3 Mt of metal reserves with 11 wt% Pb + Zn. A principal feature is that this deposit is structurally controlled by normal faults, whereas other typical deposits nearby (e.g. Maozu) are controlled by reverse faults. The origin of the Yinchanggou deposit is still controversial. Ore genetic models, based on conventional whole-rock isotope tracers, favor either sedimentary basin brine, magmatic water or metamorphic fluid sources. Here we use in situ Pb and bulk Sr isotope features of sulfide minerals to constrain the origin and evolution of hydrothermal fluids. The Pb isotope compositions of galena determined by femtosecond LA-MC-ICPMS are as follows: ²⁰⁶Pb/²⁰⁴Pb = 18.17–18.24, ²⁰⁷Pb/²⁰⁴Pb = 15.69–15.71, ²⁰⁸Pb/²⁰⁴Pb = 38.51–38.63. These in situ Pb isotope data overlap with bulk-chemistry Pb isotope compositions of sulfide minerals (²⁰⁶Pb/²⁰⁴Pb = 18.11–18.40, ²⁰⁷Pb/²⁰⁴Pb = 15.66–15.76, ²⁰⁸Pb/²⁰⁴Pb = 38.25–38.88), and both sets of data plotting above the Pb evolution curve of average upper continental crust. Such Pb isotope signatures suggest an upper crustal source of Pb. In addition, the coarse-grained galena in massive ore collected from the deep part has higher ²⁰⁶Pb/²⁰⁴Pb ratios (18.18–18.24) than the fine-grained galena in stockwork ore sampled from the shallow part (²⁰⁶Pb/²⁰⁴Pb = 18.17–18.19), whereas the latter has higher ²⁰⁸Pb/²⁰⁴Pb ratios (38.59–38.63) than the former (²⁰⁸Pb/²⁰⁴Pb = 38.51–38.59). However, both types of galena have the same ²⁰⁷Pb/²⁰⁴Pb ratios (15.69–15.71). This implies two independent Pb sources, and the metal Pb derived from the basement metamorphic rocks was dominant during the early phase of ore formation in the deep part, whereas the ore-hosting sedimentary rocks supplied the majority of metal Pb at the late phase in the shallow part. In addition, sphalerite separated from different levels has initial ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7101 to 0.7130, which are higher than the ore formation age-corrected ⁸⁷Sr/⁸⁶Sr ratios of country sedimentary rocks (⁸⁷Sr/⁸⁶Sr_200 Ma = 0.7083–0.7096), but are significantly lower than those of the ore formation age-corrected basement rocks (⁸⁷Sr/⁸⁶Sr_200 Ma = 0.7243–0.7288). Again, such Sr isotope signatures suggest that the above two Pb sources were involved in ore formation. Hence, the gradually mixing process of mineralizing elements and associated fluids plays a key role in the precipitation of sulfide minerals at the Yinchanggou ore district. Integrating all the evidence, we interpret the Yinchanggou deposit as a strata-bound, normal fault-controlled epigenetic deposit that formed during the late Indosinian. We also propose that the massive ore is formed earlier than the stockwork ore, and the temporal-spatial variations of Pb and Sr isotopes suggest a certain potential of ore prospecting in the deep mining area.     

岱崮地貌的基本特征、成因和演化

岱崮地貌是一种寒武系碎屑岩之上的平顶灰岩地貌,为中国五大地貌之一,对其研究具有地质学、古地理环境等科学意义。本文通过野外地质调查及室内研究,分析研究了岱崮地貌的特征、成因和演化,得出以下结论：1） 岱崮镇的崮主体呈NW向展布,由崮体和崮基组成。崮体包括崮顶、崮腰和崮底,崮顶为灰岩,崮腰和崮底以碎屑岩为主,崮基为前寒武系岩浆岩或太古宇泰山群;2） 近水平岩层是岱崮地貌发育的基础;3） NNW向、NW向和近EW向断层是岱崮地貌形成的根本因素,NW向和NE 向节理是主控因素,控制了岱崮地貌的走向、密度;4） 岱崮地貌古生代以来经历了多个时期的演化,经过加里东运动、海西运动和印支运动留存的寒武系-中奥陶统、上石炭统-二叠系是岱崮地貌形成的基础,燕山期中侏罗世末-晚侏罗世（162～149.8 Ma）、白垩纪（140～90 Ma）及喜马拉雅早期（65～43 Ma）产生的断层及节理是岱崮地。     

兴文侵蚀型天坑的形成演化过程研究

According to the first-hand investigation and study on Xingwen Global Geopark,the results and the data show that apart from Dayanwan and Xiaoyanwan collapsed karst Tiankeng,there are other karst landforms in Bowang Mount scenic spot such as Feiwu Cave,Dao Cave,Cangshuiyan Gorge,Nanxing TanKeng and so on.These typical karst landforms could be regarded as different vestiges of erosive karst Tiankeng of Xingwen Global Geopark,which stand for the evolutional processes of erosive karst Tiankeng separately.Moreover,the evolutional processes of erosive karst Tiankeng could be divided into the following continuous processes:an erosive karst Tiankeng develops from the processes of eroding and dissolving & extending of silo Sinkhole,and subsequently degrades to a large gorge or doline.It is worth pointing out that except for erosion of flowing water,at the same time,collapse effect has been playing extremely important role in the forming processes of these special erosive landforms.     

Pacific superplume-related oceanic basalts hosted by accretionary complexes of Central Asia, Russian Far East and Japan

Plume-related oceanic magmatism form oceanic islands, seamounts and plateaus (hereafter “seamounts” or “paleoseamounts”), which are important features in geological history. The accretion of oceanic seamounts to active continental margins significantly contributed to the formation of the continental crust. This paper reviews occurrences of Late Neoproterozoic–Mesozoic seamounts of the Paleo-Asian and Paleo-Pacific oceans, which are hosted by accretionary complexes (ACs) of Russian Altai, East Kazakhstan, Mongolia, Russian Far East and Japan. The paleoseamounts commonly consist of Ti–LREE–Nb-enriched plume-related basalts (OIB-type or intraplate basalts) capped with massive limestone and associated with other units of oceanic plate stratigraphy (OPS): oceanic floor basalts (MORB), pelagic chert, epiclastic slope facies, etc. The paper presents available geochemical data on the plume-related basalts including the first geochemical data on the Middle Paleozoic OIB-type basalts of the Paleo-Asian Ocean hosted by the Ulaanbaatar AC of Mongolia. An emphasis is made for the structural setting of OPS units, specific geochemical features of intraplate basalts, problems of their identification, and distinguishing from magmatic units of a different origin such as MORB, island-arc and back-arc basalts. Finally, we propose a continuous, though periodical, evolution of the Pacific superplume-related magmatism, which can be more reliably proved by studying Middle Paleozoic OPS units hosted by ACs of Mongolia and Tien Shan, and discuss prospects of future studies.     

New rebbachisaurid (Dinosauria: Sauropoda) material from the Wessex Formation (Barremian, Early Cretaceous), Isle of Wight, United Kingdom

Rebbachisauridae is a poorly understood clade of diplodocoid sauropod dinosaurs, currently known only from the Cretaceous of Africa, Europe and South America. European representatives are particularly rare and fragmentary. Here, we report an anterior caudal vertebra from the Barremian (Early Cretaceous) Wessex Formation of the Isle of Wight, off the southern coast of England. This specimen possesses several features known only in rebbachisaurids and shares two synapomorphies with the Afro-European taxa Demandasaurus darwini and Nigersaurus taqueti, both pertaining to the morphology of the neural spine. These features are the development of triangular lateral processes and the presence of an elliptical fossa on the lateral surface, bounded by the lateral lamina and postspinal rugosity. The Isle of Wight specimen also shares several features solely with Demandasaurus, indicating a close relationship with the Spanish taxon. These include the presence of a hyposphenal ridge, as well as an anteriorly excavated caudal rib that is restricted almost entirely to the neural arch. However, it differs from Demandasaurus in a number of ways, including the lack of excavation on the posterior surface of the caudal rib, the orientation of the neural spine, and the composition and morphology of the lateral lamina. In addition, the Isle of Wight vertebra possesses one potential autapomorphy: bifurcation of the elliptical fossa on the neural spine. However, because of the fragmentary nature of the material, a new name is not erected. Along with Demandasaurus and Histriasaurus boscarollii, this caudal vertebra indicates the presence of at least three European rebbachisaurid taxa and provides new anatomical information on this enigmatic clade of sauropod dinosaurs.     

河北省崆山白云洞成因与演化

河北省崆山白云洞发育在以中寒武统张夏组为主的碳酸盐岩地层中,平面形态主要受NNW向、NE向和近EW向断裂控制,垂向上可分为3层,各层洞穴以沿陡倾断裂侵蚀、溶蚀而成的通道相连.第一层厅堂状溶洞(天堂、人间和地府)沿NNW向断裂展布,形成于早更新世中晚期;第二层格网状洞穴(迷宫和龙宫上部)沿NNW.和NE向断裂发育,形成于中更新世中期—晚更新世初;第三层形态曲折的廊道形洞穴(龙宫下部)主要追踪NE和NNW向断裂延伸,形成于晚更新世晚期—早全新世初期.在白云洞形成发育过程中,曾经历了多次构造运动破坏.现今的白云洞,景观损毁、岩石破裂严重,灾害承受力低,因此洞穴结构稳定性保护和洞穴地质环境治理是当前重要而紧迫的任务.     

Multi‐process Late Quaternary landscape evolution modelling reveals lags in climate response over small spatial scales

Landscapes evolve in complex, non‐linear ways over Quaternary timespans. Integrated geomorphological field studies usually yield plausible hypotheses about timing and impact of process activity. Landscape Evolution Models (LEMs) have the potential to test and falsify these landscape evolution hypotheses. Despite this potential, LEMs have mainly been used with hypothetical data and rarely to simulate the evolution of an actual landscape. In this paper, we use a LEM (LAPSUS: LandscApe ProcesS modelling at mUlti dimensions and scaleS) to explore if it is possible to test and falsify conclusions of an earlier field study on 50 ka landscape evolution in Okhombe Valley, KwaZulu Natal, South Africa. In this LEM, five landscape processes interact without supervision: water driven erosion and deposition, creep, solifluction, biological weathering and frost weathering. Calibration matched model results to three types of qualitative fieldwork observations: individual process activity over time, relative process activity over time and net landscape changes over time. Results demonstrate that landscape evolution of the Okhombe valley can be plausibly simulated. A particularly interesting and persistent feature of model results are erosional and depositional phases that lag climatic drivers both by decades, and by several ka within a few hundred meters. The longer lag has not been reported for this spatial scale before and may be an effect of slow landscape‐soil‐vegetation feedbacks. The combined modelling and fieldwork results allow a more complete understanding of these responses to climate change and can fill in hiatuses in the stratigraphical record. Suggestions are made for methodological adaptations for future LEM studies. Copyright © 2009 John Wiley & Sons, Ltd.     

Electro‐Catalytic Degradation of Phenol Organics with SnO2‐Sb2O3/Ti Electrodes

The effect of extraordinary degradation of phenol organics on the SnO₂‐Sb₂O₃/Ti electrode is investigated through experimental research and theoretical analysis. The phenol organics contained 4‐chloro‐phenol, 4‐bromo‐phenol, and 2‐iodo‐phenol. At a current density of 4 mA cm^–2 and an electrolysis time of 12 h, the degradation efficiency of the phenols was over 98% with a relatively short degradation time, whereas the degradation time of the PbO₂/Ti electrode surpassed 40 h while delivering 100% disposal efficiency. Therefore, the effectiveness of electrochemical (EC) oxidation by the SnO₂‐Sb₂O₃/Ti was superior to that of the PbO₂/Ti electrode. At the same time, the SnO₂‐Sb₂O₃/Ti had higher oxygen generation potential and lower electron consumption than the other electrodes. This was mainly due to the effect of the middle Sb₂O₃ layer, which due to its high porosity and good catalytic effect, contributed to a better catalysis than the SnO₂ part.     

华北地下水位强震短期异常演化及前兆判别标志研究

对地下水位地震前兆异常开展了参数提取方法的研究, 并以其提取的结果为输入, 对1984～2002年华北地区地下水位异常参数分布做了全时空扫描, 继而将全部图像与华北地区构造活动性量化评估的数字化图像进行了叠加, 实现了地下水位异常动态扫描与区域构造活动性背景的结合。 在此基础上, 对1985年以来华北地区5级以上地震前的地下水位短期图像演化情况做了全面分析, 提取出了判别异常区的指标以及地震短期异常区的演化特征, 并最终建立了华北地区强震前地下水位短期前兆的判别标志。     

RIVER PATTERNS AND SPATIAL AND TEMPORAL TRANSFORMATION MODES

1 INTRODUCTIONThe river pattCths and transfo~ion of the pattenes are of great significance for flood control andmanagement of navigation system. Vallous spatial and temporal modes have been reported in theprevious stUdies. These modes depend on certain controlling factors and occur with different frequencies.These factors are related to modem fluvial processes and ancient sedimentary consequences. T'hedifferent river patterns, depending on the factors, can be either observed in nature or…