陕西庞家河金矿成矿地质特征及成矿物质来源研究          下载免费PDF全文

吴孔运  高利鹏 《中国地质》2011,38(3):716-723

庞家河金矿产于既是矿源层又是赋矿主岩的上泥盆统下东沟组绢云千枚岩、变质砂岩中。金矿体主要赋存在膨胀、收缩、分枝、复合及波状弯曲的层间挤压片理化带中。矿体形态简单,主要为似层状、板状及透镜状,矿体沿走向较稳定,但倾向及倾角变化较大。主要金矿物为自然金、银金矿,载金矿物为黄铁矿及毒砂。主要围岩蚀变是中低温黄铁矿化和毒砂化。成矿期主要分为3个不同的阶段,即:石英-粗粒黄铁矿-水云母阶段、细粒黄铁矿-毒砂阶段和黄铁矿-石英-碳酸盐阶段。此外,通过对庞家河金矿硫、氧及铅稳定同位素分析,发现矿石铅主要来源于上地壳,部分来源于地幔。δ34S值揭示了金成矿流体主要来源于地壳流体,部分起源于岩浆。同样,δ18O值显示成矿热液部分来源于岩浆水,大部分来源于变质水。总之,庞家河金矿成矿物质来源是储库混合源。  相似文献   

Relationships between surface-active organic substances, chlorophyll a and nutrients in the northern Adriatic Sea     

Bla?enka Gašparovi?  Tamara DjakovacNataša Tepi?  Danilo Degobbis 《Continental Shelf Research》2011,31(10):1149-1160

Surface-active organic substances (SAS), nutrients, chlorophyll a (Chl a), dissolved oxygen (O₂), salinity (S) and temperature (T) were measured approximately monthly in the northern Adriatic Sea (NA) during two years. Results were elaborated for two stations of different trophic status. Exhaustive statistical examinations of measured variables were performed to contribute to better understanding of the processes and interdependence of the measured parameters. The results of those analyses allowed the region to be described based on several groups of data relevant for particular processes. Chl a appear to be independent parameter; orthosilicate, nitrite and ammonium represent the parameter group most relevant for regeneration processes; the second group includes nutrients dominant in freshwater inputs (orthophosphate and nitrate), while in the third group are parameters related to primary production processes (T, O₂, organic phosphorus and SAS). Probably due to time lags between nutrient uptake and phytoplankton growth as well as between cells growth/division and SAS release, both, the correlation between nutrients and Chl a and the correlation between Chl a and SAS were not statistically significant. Although significantly higher nutrient and Chl a concentrations were found in the mesotrophic western part of the region in comparison to the oligotrophic eastern part, the SAS concentration differences were less marked. It is assumed that more OM is produced, but also at the same time remineralized, at the mesotrophic western part, leading to higher concentrations of regenerated nutrients there. Presence of different phytoplankton taxa and/or fractions (micro and nano) at the two stations may have also contributed to minimize the difference in SAS contents. Higher SAS acidities were noticed in the mesotrophic than in the oligotrophic part.  相似文献   

甘肃古浪长岭山北麓断裂新活动特征与地震危险性   总被引：1，自引：0，他引：1       下载免费PDF全文

刘强  王爱国  邵延秀  赵泽贤 《地震工程学报》2011,33(2):123-129

通过野外调查和探槽开挖,并结合b值计算结果,对位于甘肃省中部古浪县的长岭山北麓断层的几何学、运动学特征、活动性分段及地震危险性进行了研究.研究认为长岭山北麓断裂主要由四条断层组成,总体呈反“S”形展布;断层最新活动在西段f1表现为倾向南的左旋正断性质,在西段f2和中段f3表现为向北倾的左旋正断性质,东段f4又转变为倾向南的左旋正断活动性质,断裂西端以秦家大山南北向隆起及第三系褶皱与古浪断裂隔断,东端以白墩子左旋拉张盆地与罐罐岭断裂左阶排列,阶距3.5 km;断裂带全新世早中期以来有过地震活动,最后一次活动离逝时间较长,现代应力积累较快,为未来地震危险区.  相似文献   

青藏高原北部地区地震基本活动状态定量评价   总被引：3，自引：1，他引：2       下载免费PDF全文

刘小凤  梅秀苹  冯建刚  程建武  张辉 《地震工程学报》2011,33(2):130-136

基于区域构造背景、应力场状态及动力学环境等,将青藏高原北部地区划分为4个相对独立的统计单元,即祁连山地震带、甘东南地区、柴达木一共和地块及库玛地震带.通过地震频度和b值拟合确定了各个地区不同下限震级的地震目录完整性起始时间;确定了各构造单元中强以上地震活跃与平静交替活动的特征;定量计算了在平均状态中强以上地震活动特征参数及平静阶段与活跃阶段地震活动特征参数;分别获得了各个区域在平均、活跃与平静状态下的小震活动状态参数.  相似文献   

陕西地区地震动衰减关系研究     

范文  杜文和  王晓军  邵辉成  文毅 《地震工程与工程振动》2011,31(2):47-54

通过分析陕西省丰富的地震活动资料,包括鲜明的地震活动与震害分布的地域性特点以及地震地质环境特点,将陕西省分为三个分区,来进行地震动衰减关系的研究.研究内容主要包括地震烈度衰减关系和基岩地震动衰减关系.选择美国西部作为参考区,三个分区分别作为研究区,采用可逆法进行映射转换计算,得到了三个分区的基岩地震动衰减关系,在转换过...  相似文献   

基于多源遥感数据的生态系统保育土壤价值评估——以河北省北部四地市为例   总被引：1，自引：0，他引：1  

许旭  李晓兵  韩念龙 《国土资源遥感》2011,(3):123-129

为了给合理地利用土地资源和科学地进行环境保护提供依据,利用多源遥感影像数据,结合气象数据、土壤属性数据与DEM,对河北北部地区生态系统的土壤保持量进行了评估,并参考《森林生态系统服务功能评估规范》,对生态系统保护土壤肥力的价值与固土价值进行了评估.结果表明,研究区2008年度生态系统的土壤保持总量达到7.55亿t,对应...  相似文献   

东亚地区北方气旋和南方气旋活动频数的时空特征     

王艳玲  王黎娟 《辽宁气象》2011,(6):43-48

利用1953-2007年NCEP／NCAR再分析逐日海平面气压场资料,统计分析东亚地区北方气旋和南方气旋的时间和地域分布特征。结果表明：南、北气旋活动频数存在明显的年际和年代际变化,伴随着一次全球性的年代际气候跃变,20世纪80年代初期北方气旋活动频数出现了显著的突变。从月际分布可知,5月北方气旋频数最多,8月南方气旋频数最多;春季北方气旋活动频繁,存在着明显的两个高值中心,分另Ij位于蒙古国中部和中国东北地区北部;夏季南方气旋活动频繁,主要集中在中国东部沿海及日本南部海面。南北气旋活动频数的季节变化与大气环流的变化密切相关。相关统计结果可增加对东亚温带气旋活动规律的认识和了解,并为预测和预报提供参考。  相似文献   

陕西省能源供给与经济及生态环境协调性分析     

沈明  沈镭  张超  刘立涛  钟帅 《地域研究与开发》2015,(1)

作为我国能源供应的战略基地和大西北生态脆弱区,陕西省经济增长和生态环境协调能力关乎国家能源和生态安全,探究陕西省能源供给与经济及生态环境发展(3E)的协调性及关联性具有重要的理论和现实意义。以能源供给为切入点对陕西省3E现状进行定性分析,推断能源供给对陕西省经济增长的结构性支撑作用。选取25个指标构建3E指标体系,运用层次分析、模糊综合评价等方法对各子系统发展水平及各子系统之间协调性进行定量分析。结果表明:(1)陕西省能源供给、经济增长与生态环境间具有较高的协调性;(2)陕西省能源供给、经济增长和生态环境协调关系波动大;(3)能源供给、经济增长和生态环境协调度对能源供给变化具有较高的敏感性。  相似文献   

Shell‐shape and morphometric variability in Mytilus galloprovincialis from micro‐tidal environments: responses to different hydrodynamic drivers          下载免费PDF全文

Vanessa Moschino  Monica Bressan  Luigi Cavaleri  Luisa Da Ros 《Marine Ecology》2015,36(4):1440-1453

Tidal conditions differently influence inter‐tidal organisms in terms of general physiological and metabolic responses. In this study we investigated the morphological response in shells of Mytilus galloprovincialis native to different micro‐tidal coastal environments in the Northern Adriatic Sea. Our purpose was to highlight the ecophenotypic variability across tidal levels and to elucidate how tidal currents and waves produced by anthropogenic activities may play a part in modulating shell morphology. Three sampling sites were selected: an open‐sea area 15 km off‐shore and two sites within the lagoon of Venice, the first near one of its three inlets, and the other one in the proximity of Venice city centre. At each sampling site, organisms were seasonally collected at different depths within their vertical zonation, either in the inter‐tidal zone – i.e. at both the highest and lowest tide zonation limits, and subtidally. The mussel shells were analysed by investigation of their morphometric relationships (height/length and width/length ratios) and by elliptic Fourier analysis of the shell contours. Shell thickness and condition index were also evaluated for a better comprehension of energy allocation/partitioning. Estimates based on long‐term measurements, visual observation, wind statistics and wave growth laws allowed an evaluation of the forces acting on shells. At the open‐sea site, the observed phenotypic variability of both shell shape and thickness was clearly related to the tidal vertical zonation. At the two lagoon sites, the currents generated by tidal flow through the inlet and the waves caused by the frequent passage of boats influenced both shell shape and thickness. A trade‐off between protection and growth was apparent along the tide gradient, as emphasized by the differences in the partitioning and allocation of energy between shell and flesh production.  相似文献   

塔里木盆地下寒武统肖尔布拉克组北部台缘带展布及其油气勘探意义   总被引：3，自引：2，他引：1  

熊益学  陈永权  关宝珠  邓力萍  倪新锋  熊冉 《沉积学报》2015,33(2):408-415

礁滩型白云岩是世界范围内油气勘探开发效果最好的领域之一。塔里木盆地震旦-寒武系具备规模礁滩型白云岩发育基础,但其特征与分布研究基础十分薄弱。本文采用野外剖面观察、单井资料分析、地震资料刻画等手段,落实了柯坪-塔北西部存在下寒武统台缘带,命名为北部台缘带,该台缘带呈北东走向,长约330 km,宽约7 km。野外露头资料显示,下寒武统北部台缘带发育两期微生物礁,岩性以针孔状白云岩为主,溶蚀孔洞发育;地震剖面上,可见丘状前积反射特征。北部台缘带具有得天独厚的生储盖配置优势,位于长期继承性发育的古隆起之上,具备形成大油气田的有利条件。北部台缘带的展布特征为该区下古生界白云岩的区带评价及目标优选指明了方向。  相似文献