Recognition of an enhanced multi-element geochemical signature of porphyry copper deposits for vectoring into mineralized zones and delimiting exploration targets in Jiroft area,SE Iran     

《Ore Geology Reviews》2017

Delimiting exploration targets using geochemical exploration data can be a challenging issue when different geochemical signatures represent the same deposit-type sought. In this regard, fuzzy operators have been used to integrate different geochemical evidence layers into a single model for generating target areas. In this paper, a GIS-based expected value function was adapted to integrate different geochemical evidence layers into a stronger geochemical signature for delimiting exploration targets. Then, the expected value function and fuzzy operators were compared. The comparison demonstrated that the former is more efficient than the later for generating a stronger geochemical evidence layer. The higher efficiency of the expected value function is because it simultaneously uses the value of all input variables and their relative importance in the process of integration. The proposed approach was evaluated by using a lithogeochemical data set for prospecting porphyry-Cu deposits in Jiroft area, Kerman province, southeast of Iran, as a case study.  相似文献   

基于证据权法的公路路基岩溶塌陷危险性评价          下载免费PDF全文

孙琳  任娜娜  李云安  胡乐健 《中国地质灾害与防治学报》2019,30(3):94-100

将证据权模型应用在公路路基岩溶发育强度分区中,在工程作用下岩溶强发育区易发生岩溶塌陷。介绍了证据权模型的方法。在丹霞枢纽互通区域,应用Arc GIS将研究区划分为5m×5m的栅格,考虑地层岩性、地下水距地面距离、顶板厚度、距断层距离4个证据因子,然后进行证据因子优选,通过叠加分析,得出岩溶发育强度的后验概率,并进行条件独立性检验,利用CAPP曲线确定阈值将后验概率分区。应用ROC曲线进行预测的精度评价,预测正确概率为66.2%。最后结果表明,证据权模型应用在公路路基岩溶方面可行。  相似文献   

Lithodiversity and Its Spatial Association with Metallic Mineral Sites,Great Basin of Nevada     

Mihalasky  Mark J.  Bonham-Carter  Graeme F. 《Natural Resources Research》2001,10(3):209-226

Geographical information system (GIS) techniques were used to investigate the spatial association between metallic mineral sites and lithodiversity in Nevada. Mineral site data sets include various size and type subsets of about 5,500 metal-bearing occurrences and deposits. Lithodiversity was calculated by counting the number of unique geological map units within four sizes of square-shaped sample neighborhoods (2.5-by-2.5, 5-by-5, 10-by-10, and 20-by-20 km) on three different scales of geological maps (national, 1:2,500,000; state, 1:500,000; county, 1:250,000). The spatial association between mineral sites and lithodiversity was observed to increase with increasing lithodiversity. This relationship is consistent for (1) both basin-range and range-only regions, (2) four sizes of sample neighborhoods, (3) various mineral site subsets, (4) the three scales of geological maps, and (5) areas not covered by large-scale maps. A map scale of 1:500,000 and lithodiversity sampling neighborhood of 5-by-5 km was determined to best describe the association. Positive associations occurred for areas having >3 geological map units per neighborhood, with the strongest observed at approximately >7 units. Areas in Nevada with more than three geological map units per 5-by-5 km neighborhood contain more mineral sites than would be expected resulting from chance. High lithodiversity likely reflects the occurrence of complex structural, stratigraphic, and intrusive relationships that are thought to control, focus, localize, or expose mineralization. The application of lithodiversity measurements to areas that are not well explored may help delineate regional-scale exploration targets and provide GIS-supported mineral resource assessment and exploration activity another method that makes use of widely available geological map data.  相似文献   

鄂尔多斯东北缘早白垩世冰川泥石流沉积的发现及其成因证据   总被引：11，自引：0，他引：11  

程守田  李志德  黄焱球  葛利刚  刘星 《地质科技情报》2002,21(2):36-40

冰川泥石流是由冰碛物与冰雪融水混合形成的一种碎屑重力的沉积。综合泥石的砾石成分、冰川擦痕、冰冻痕、巨型漂砾等及其某些沉积特征和源区地质背景，认为鄂尔多斯东北缘早白垩世泥石流沉积为冰川泥石流成因，这一发现暗示了晋北隆起在早白垩世曾有山谷冰川存在，并对我国白垩纪陆地古冰川及其古气候研究具有重要意义。  相似文献   

Drought, desiccation and discourse: missionary correspondence and nineteenth-century climate change in central southern Africa   总被引：1，自引：0，他引：1  

Endfield GH  Nash DJ 《The Geographical journal》2002,168(1):33-47

This paper examines the role that representatives of the London Missionary Society in central southern Africa during the nineteenth century may have played in the development of geographical debates concerning the long-term desiccation of the African continent. Observations on climate included within missionary documents are used to reconstruct a chronology of intra-decadal climatic variability for the period 1815–1900. This reveals six drought periods and seven wet phases that affected large areas of the region, but identifies no evidence for progressive desiccation. The chronology is then used as a framework within which to view missionary perspectives on drought and desiccation. Major influences upon the development of desiccationist theory appear to include the prevalence of contemporary moral economic explanations of climatic variability, as well as the uptake and acceptance of indigenous understanding of climate change. Significantly, many of the key observations by eminent missionaries used as supporting evidence for progressive desiccation are identified as having been made during periods of severe drought. This is used to suggest that the most widely propagated evidence for desiccation may, therefore, simply be the end-product of periods of short-term drought rather than long-term climatic deterioration.  相似文献   

陕西秦巴地区金矿潜力区预测与评价          下载免费PDF全文

邢学文  陈守余 《地质找矿论丛》2003,18(2):103-107,112

在了解秦巴地区地层、构造和侵入岩体等地质背景的基础上，深入分析了该区已知金矿床的控矿地质因素。以控矿地质因素作为致矿证据层，应用证据权法对研究区进行成矿预测，圈定了7个金矿远景区并进行了远景评价。  相似文献   

苏鲁地区地壳岩浆底侵的地球物理判识   总被引：25，自引：3，他引：25       下载免费PDF全文

杨文采 《地质学报》2002,76(2):173-179,T003

底侵作用是研究壳幔物质交换与大陆增生演化的重要机制之一，但是对岩浆底侵作用的判识是十分困难的科学问题，中国大陆科学钻探先行项目在苏鲁地区积累的地震学，地热学及地电学资料表明，在苏鲁地区发生过与大陆裂谷同期的地幔岩浆底侵作用，发生了时段主要为始新世，它的发育与沿嘉山－晌水大陆裂谷带在时空上有密切联系，这里的壳幔过渡带厚度可达3km，推测为橄榄岩与基性麻粒岩互层。结合岩石学资料可以推算出由浆底侵作用造成大陆地壳增厚的平均速度约为0.1mm/a.  相似文献   

Geological and Geochemical Evidence for Discriminating Anatectic and Subsolidus Migmatites in the Dabieshan Complex,Northeastern Hubei Province     

王江海  张丽彦等 《中国地球化学学报》1997,16(2):112-122

Based on the geological and geochemical information about migmatites,the following lines of evidence have been proposed for discriminating the anatectic leucosome in the Dabieshan Complex:(1)its width is larger than that derived from the subsolidus genesis,cutting across regional foliation,thus giving rise to complicated folds and wider selvages;(2)it is composed of melanic and accessory minerals in addition to quartz and feldspars;(3)the significant dfference in anorthites of plagioclase between paleosome and leucosome;(4)temperature and pressure(P/T) conditions revealed by the mineral compositions and assemblages are over those for the onset of anatexis;and (5)it is enriched in the major elements(e.g.Al2O3.Fe2O3and TiO2)and immobile and incompatible elements(e.g.LREE,Th,Hf and Zr).Finally,by combining the geological and geochemical features with the statistical data for the spatial distribution of minerals and mass-balance in the migatites,it is concluded that anatexis is the cardinal mechanism of migmatization in the Dabieshan Complex.  相似文献   

Petrologic and Geochemical Characteristics and Origin of Gusui Cherts,Guangdong Province,China     

EDWARDH.CHOWN  EDWARDH.CHOWN 《中国地球化学学报》1994,13(2):118-131

The characteristic structures of the Precambrian cherts from the Gusui section, Guangdong ,Chi-na, include bedded structure ,laminated structure ,massive structure and pseudobrecciated structure.The chert is characterized by consistently low abundance of TiO2,Al2O3 and most trace elements.Howevver ,it is enriched in Ba,As,Sb,Hg and Se.In Al-Fe-Mn ternary diagrams,it falls into the “hydrothermal field“ .Correspondence analysis and factor analysis show that many elements show up in the factor that represents the leaching of country rocks by hydrothermal solutions,and are the very characteristic element association fo the geochemically anomalous South China basement.Petrologic and geochemical evidence suggests a hydrothermal origin for the chert.The chert may have been formed in a Precambrian fift or an extension zone developed within the Yunkai marginal geosyncline, with a fault system linking it to an unknown heat source at depth.  相似文献   

Groundwater arsenic pollution from Inner Mongolia and evidence of its occurrence     

《中国地球化学学报》2006,25(B08):9-10

  相似文献