桂北地区锡多金属矿找矿方向     

黄惠民  树皋 《南方国土资源》2002,15(4):17-22

文章通过对前人资料的收集整理 ,结合大调查项目的找矿成果和信息分析 ,认为桂北地区锡多金属找矿前景乐观 ,远景区可划分为二区 (九万大山、越城岭 )三带 (丹池、观音阁、花山—姑婆山 ) ,找矿重点应放在 3条成矿带上。  相似文献   

Miocene provenance change in Himalayan foreland basin and Bengal Fan sediments,with special reference to detrital garnet chemistry     

Kohki Yoshida  Toru Nakajima  Yuki Matsumoto  Ai Osaki  Lalit Kumar Rai  Jarrett W. Cruz  Harutaka Sakai 《Island Arc》2021,30(1):e12408

Bengal Fan Miocene sediments were collected during International Ocean Discovery Program Expedition 354 and investigated using petrographic and detrital garnet chemistry analyses. The Miocene Siwalik Group, which is composed of sediments deposited in the Himalayan foreland basin, was also analyzed for comparison with the Bengal Fan data for the provenance change during the Miocene. Our petrographic analyses revealed that the Miocene sediments of the Bengal Fan and Siwalik Group consist predominantly of Higher Himalayan Crystalline (HHC)-derived detritus such as chloritoid, staurolite, sillimanite, and/or kyanite, which appear among the accessory minerals. The chemistry of the detrital garnet varies across the stratigraphy; most of the garnet is rich in almandine and poor in spessartine and pyrope. However, pyrope-rich garnet, which is considered to originate from the HHC core (granulite facies), was found in the lower to upper Miocene deposits. The deposition of HHC-derived detrital garnet began before the Middle Miocene (15 Ma) and before the Late Miocene (10–9 Ma) in the Siwalik Group. The Bengal Fan data, by contrast, indicated that pyrope-rich garnet appeared in the Early Miocene (17.3 Ma) and Late Miocene (8.5–6.5 Ma). We conclude that the Bengal Fan sediments record the erosion of the HHC zone since the Early Miocene that appears in the Siwalik sediments. Furthermore, we found that the HHC-derived inputs decreased from the late Middle Miocene (12 Ma) to the early Middle Miocene (10 Ma) in both the Nepal Himalaya foreland basin and the Bengal Fan. The disappearance of the HHC-derived detritus is probably the result of dilution by Lesser Himalayan detritus, which suggests that the Lesser Himalayan zone, which is composed of metamorphosed and unmetamorphosed sedimentary rocks, was uplifted.  相似文献   

从破冰船强制领航到许可证制度——俄罗斯北方海航道法律新变化分析          下载免费PDF全文

张侠  屠景芳  钱宗旗  王泽林  杨惠根 《极地研究》2014,26(2):268-275

围绕北方海航道定义和破冰船强制领航两个重要的争议问题,详细对比了俄罗斯相关旧法律条文和2013年颁布的新法律条文,综合分析后认为:(1)在法律层面上,俄罗斯对于北方海航道属于国家历史性交通干线的立场没有改变,范围则做了明晰化的界定,新的北方海航道水域范围与俄罗斯北冰洋内水、领海及毗连区和200海里专属经济区水域范围相一致。这意味着消除了有关北方海航道北部边界是否延伸到公海的争议;(2)在规则层面上,从破冰船强制领航制度改变为许可证制度,尤其是给出了具体的、可操作和可预期的独立航行许可和不许可条件,使得外国船只在北方海航道水域的独立航行成为可能。由此得出结论:俄罗斯北方海航道政策出现了较大变化,有进一步向国际开放的政策倾向。  相似文献   

山体效应对北半球林线分布的影响(英文)     

赵芳  张百平  庞宇  姚永慧 《地理学报(英文版)》2014,(2)

Alpine timberline, as the "ecological transition zone," has long attracted the attention of scientists in many fields, especially in recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However, these models are usually on regional scale and could not be applied to other regions; on the other hand, hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline, and takes latitude, continentality and mass elevation effect(MEE) as independent variables and timberline elevation as dependent variable to develop a ternary linear regression model. Continentality is calculated using the meteorological data released by WorldClim and mountain base elevation(as a proxy of mass elevation effect) is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination(R2) of the linear model is as high as 0.904, and that the contribution rate of latitude, continentality and MEE to timberline elevation is 45.02%(p=0.000), 6.04%(p=0.000) and 48.94%(p=0.000), respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude differs in different regions, e.g., 50.49%(p=0.000) in North America, 48.73%(p=0.000) in the eastern Eurasia, and 43.6%(p=0.000) in the western Eurasia, but it is usually very high.  相似文献   

北祁连西段早古生代构造演化史   总被引：21，自引：2，他引：21  

左国朝  毛景文 《甘肃地质》1999,8(1):6-13

北祁连西段与北祁连中段构造带之间被一条平行于阿尔金断裂带的宗宾大坂古转换断裂所隔，东西两段在早古生代构造演化史上有明显差异。北祁连西段早古生代构造是在前震旦系陆壳基底上，在震旦纪再一次开裂演变为裂陷槽，寒武—奥陶纪为裂谷—海沟—火山弧多元构造的格局  相似文献   

Analysis of the effects of different storm events on shoreline dynamics of an artificially embayed beach     

Renata Archetti  Claudia Romagnoli 《地球表面变化过程与地形》2011,36(11):1449-1463

A five‐year dataset of Argus‐derived mean intertidal positions has been analysed to characterize the shoreface variability in a beach protected by a system of groynes and a parallel low crested structure (Lido di Dante Ravenna, Italy). For the period 2004–2009, 84 intertidal beach bathymetries and shorelines at the zero sea level were used as indicators to assess beach changes in between a number of selected surveys and to determine characteristic patterns of the beach response to storm events from different directions. Variations in the shoreline at the zero sea levels have been quantified and analysed in conjunction with nearshore wave conditions and provenance linked to storm events. These fall into two categories: (1) storm events occurring during Bora (north‐eastern) wind conditions and (2) storm events occurring during Scirocco (south‐eastern) wind conditions. The results show that, apart from main beach advances of the whole protected beach due to nourishments periodically carried out, a marked variability is observed among the four sub‐cells into which the shoreface behaviour has been separately analysed. In particular, a dependence of beach rotation in the ‘artificially embayed’ area on the substantially bi‐directional wave climate has been shown: Bora and Scirocco storm events produce shoreline rotation in counterclockwise and clockwise directions, respectively, due to the occurrence of longshore currents in the opposite direction in the nearshore. An attempt was made to correlate the shoreface dynamics for the main rotation events (14 selected ones) to the wave attack intensity (as the total energy flux due to storm events). A relationship seems to occur (for each storm category) between the shoreline displacements estimated for each sub‐cell and the total energy flux computed for inter‐survey periods, supporting the occurrence of a link between the observed morphological changes and the hydrodynamic forcing associated with storm events in the five‐year monitoring period. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Bacterioplankton dynamics along the gradient from highly eutrophic Pearl River Estuary to oligotrophic northern South China Sea in wet season: implication for anthropogenic inputs   总被引：3，自引：0，他引：3  

Zhou W  Long A  Jiang T  Chen S  Huang L  Huang H  Cai C  Yan Y 《Marine pollution bulletin》2011,62(4):726-733

Bacterioplankton abundance (BA) and biomass (BB) from the eutrophic Pearl River Estuary (PRE) to the oligotrophic northern South China Sea (NSCS) were studied in the wet season. BA was significantly higher (p < 0.05) in PRE (12.51 ± 3.52 × 10⁸ cells L⁻¹), than in the continental shelf neritic province (CSNP, 4.95 ± 2.21 × 10⁸ cells L⁻¹) and in the deep oceanic province (OP, 3.16 ± 1.56 × 10⁸ cells L⁻¹). Nutrient-replete PRE waters (DIN > 100 μM and PO₄ > 1 μM) resulted in high chl a and BB, whereas nutrient-depleted offshore waters (DIN <5 μM and PO₄ < 0.5 μM) had low biomass. Temperature (>26 °C) was not the controlling factor of BA. BB was significantly correlated with chl a biomass both in PRE and NSCS. The bacteria to phytoplankton biomass (BB/PB) ratio increased clearly along the gradient from near-shore PRE (0.15) to offshore CSNP (0.93) and deep OP (2.75), indicating the important role of small cells in the open ocean compared to estuarine and coastal zones.  相似文献   

Geochemistry and origin of rare earth elements (REEs) in the Shengli River oil shale, northern Tibet, China   总被引：4，自引：0，他引：4  

Xiugen Fu  Jian Wang  Yuhong Zeng  Fuwen Tan  Jianglin He 《Chemie der Erde / Geochemistry》2011,(1):21-30

The Shengli River-Changshe Mountain oil shale zone, located in the North Qiangtang depression, northern Tibet plateau, represents a potentially large marine oil shale resource in China. Twenty-eight samples including oil shale, micritic limestone and marl were collected from the Shengli River area to determine the contents and distribution patterns of rare earth elements (REEs) in marine oil shale. Oil shale samples from the Shengli River area have high ash yield (61.86–67.48%) and TOC content (8.02–13.67%) with low total sulfur (S_t,d) content (0.76–1.39%) and intermediate shale oil content (3.60–16.30%). The total rare earth element (ΣREE) content in oil shale samples is notably depleted (46.79–67.90 μg/g), approximately one third of the mean value of the North American Shale Composite (NASC), and lower than that of world-wide black shales and Chinese coals, but higher than that of world-wide coals and micritic limestone samples (29.21 μg/g) from the Shengli River area. The oil shale samples from the Shengli River area exhibit shale-like Chondrite or NASC-normalized REE patterns similar to those of micritic limestone and marl samples from this area, indicating that REEs of these different lithological samples may have been derived from a similar terrigenous source.REE contents of oil shale samples are highly positive correlated with ash yield and show a positive correlation with Fe and a weakly positive correlation with organic sulfur, and the vertical variations of REEs mainly follow those of Si, Al, K and Ti. All these facts indicate that the REE contents in oil shale seams are mainly controlled by clay minerals and, to a lesser extent, by pyrite, as well as partly associated with oil shale organic constituents. Rare earth elements in the Shengli River oil shale have originated from two sources: a felsic volcanic rock source and a clastic or/and limestone source.  相似文献   

河北临漳曹村窑址青釉器物工艺特征研究     

陈岳  罗武干  穆青  赵学峰  王昌燧 《岩矿测试》2013,32(1):64-69

河北地区古代瓷窑产品的理化测试工作多集中于隋唐、宋金时期的器物,北朝等早期产品的分析数据则少有报道。本文运用X射线荧光光谱、X射线衍射、岩相、吸水率测试和烧成温度测定等分析方法,对曹村窑址出土青釉样品的工艺特征开展研究。结果表明,2件样品釉层氧化钙含量分别为17.86%和14.1%,烧成温度分别达到1150.1℃和1185.2℃,证明这2件样品属于青瓷,从而证实了曹村窑是已发现的我国北方早期烧制青瓷的窑口之一;其余样品釉层氧化铅含量大于42%,部分样品吸水率低于5%,X射线衍射结果显示胎体中出现莫来石相,证明曹村窑可以生产出瓷胎铅釉陶。结合样品烧成温度均在1000℃以上,远高于铅釉成熟温度,推断曹村窑的瓷胎铅釉陶在北朝时期已经使用了二次烧成工艺。这一复杂工艺的产生,有可能为唐三彩的出现作了技术铺垫。  相似文献   

辽东湾地区辽中北洼超压的发育演化 及油气幕式成藏     

彭波  郝芳  邹华耀 《地质论评》2013,59(6):1257-1267

基于地层测试数据,利用声波时差的等效深度法以及数值模拟方法对辽中北洼地区超压的分布和演化进行了研究。结果表明本区超压普遍发育,储层超压主要发育于古近系及潜山,最大压力系数193;东二下亚段及以下地层泥岩段中普遍发育欠压实,计算压力系数可达到19以上。不均衡压实和生烃作用是泥岩层超压发育的主要成因,它源传导型是储层超压发育的主要机制。沙河街组沉积以来,烃源岩中超压开始发育并逐渐增加,东营组沉积末期达到高峰,随后开始泄放降低,明下段沉积期开始,超压再次积累增大直至现今。JZ20 2凝析气田的储层流体包裹体及温压方面的证据、油气成熟度和烃源岩生烃史方面的证据以及原油物性方面的证据表明其油气成藏为晚期幕式快速充注成藏。同时研究区断裂发育少,活动性弱,油气沿断层垂向运移受限,充注期主力烃源岩发育强超压,产生水力破裂微裂缝成为油气幕式排放的通道,同时为油气长距离的侧向运移提供了充足的动力,属于超压主导型油气晚期幕式快速成藏。  相似文献