共查询到20条相似文献，搜索用时 15 毫秒
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Weathering intensity changes due to climatic variability across tectonically stable portions of continental crust can generate a thick and extensive weathered cover, resulting in regolith-dominated terrains (RDTs). Mineral exploration in RDTs is challenging because of the lack of bedrock outcrop, and the difficulty of linking surface regolith geochemistry to the geology at depth. Complex weathering obscures the expression of the basement geochemistry in the regolith, and therefore the footprints of mineral systems are difficult to detect. The southeast of the Yilgarn Craton and the Albany–Fraser Orogen (AFO) in the south of Western Australia is an RDT that extends along the coastline and the Eucla basin.This study proposes a landscape evolution model of the AFO, driven by transgression–regression sea-level changes that resulted in the formation of numerous islands and development of estuarine zones. This model contrasts with the river system-dominated landscape evolution present in the Yilgarn Craton. This difference has significant implications for mineral exploration and geochemical interpretation of the regolith in this region.Weathering profiles developed “on inland” and “on island” are thicker and more mature than those developed in sea-inundated areas. Even if in the Yilgarn Craton local areas display reworking of weathering profiles and other complexities from Permian, non-marine Tertiary sediments and Quaternary fluvial and aeolian sediments, at a regional scale, if vertical geochemical mobility of elements has occurred, “on inland” and “on island” are more reliable for understanding geochemical anomaly-basement relationships, whereas the “marine inundated” areas require a more detailed investigation, because of the role of marine reworking of weathering profiles and possible mixture of sediments from different provenances.Landscape changes from the topographically high, dissected Yilgarn environment with thick saprolite development and uneven basement topography, to the nearly flat regions dominated by sand dunes and thin saprolite development at the coastline. These regions are the result of the erosional and depositional effects of successive sea-level transgression–regression cycles. Within this framework, the following four different regolith settings have been identified in a progressive change from Yilgarn Craton environments to the modern coastline: (1) Albany; (2) Kalgoorlie–Norseman; (3) Esperance; and (4) Neale.Mapping the palaeocoastlines, islands and estuarine zones, as well as the region of influence of marine limestones and sediments, can significantly improve the understanding of how surface geochemistry relates to the landscape, and how it links with the geology at depth, and therefore, how it may reflect the presence of mineral systems. Understanding the difference in the landscape evolution between the AFO and Yilgarn Craton is essential to properly calibrate mineral exploration protocols in both regions. 相似文献
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A. Porwal I. González-Álvarez V. Markwitz T.C. McCuaig A. Mamuse 《Ore Geology Reviews》2010,38(3):184-196
Bayesian weight-of-evidence and logistic regression models are implemented in a GIS environment for regional-scale prospectivity modeling of greenstone belts in the Yilgarn Craton, Western Australia, for magmatic nickel sulfide deposits. The input variables for the models consisted of derivative GIS layers that were used as proxies for mappable exploration criteria for magmatic nickel sulfide deposits in the Yilgarn. About 70% of the 165 known deposits of the craton were used to train the models; the remaining 30% was used to validate the models and, therefore, had to be treated as if they had not been discovered. The weights-of-evidence and logistic regression models, respectively, classify 71.4% and 81.6% validation deposits in prospective zones that occupy about 9% of the total area occupied by the greenstone belts in the craton. The superior performance of the logistic regression model is attributed to its capability to accommodate conditional dependencies amongst the input predictor maps, and provide less biased estimates of prospectivity. 相似文献
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AbstractThe Yilgarn Craton of Western Australia hosts a number of Cenozoic paleochannels, which have been incised into the underlying Paleozoic and Precambrian rocks, filled with sediments and subsequently weathered. The paleochannels are of particular interest in mineral exploration as they may not only host placer-type deposits but also overlie significant supergene and primary mineralisation. Paleochannels also pose particular challenges during exploration as they mask underlying geochemical anomalies, including gold and pathfinder elements. This study investigates a method of distinguishing transported overburden from residual regolith utilising a combination of field and laboratory-based techniques. At the Minotaur deposit, the residual regolith and transported overburden are mineralogically similar, although the presence of biotite, chlorite and muscovite is more characteristic of the residual regolith. Geochemically, Zr, Ti, Co and Sc ratios form distinct groupings allowing more confident discrimination of transported overburden from the underlying residual regolith units. The presence of a distinct gold depletion zone at the redox front was also identified to be a feature of the Minotaur deposit, with Au enrichment occurring above (within transported overburden) and below (within saprolite) the redox front, similar to other gold deposits on Lake Lefroy. The lithological, stratigraphic and Au-enrichment characteristics at Minotaur have also been compared with regional studies and suggest the long-lived impact of paleovalleys on the depositional systems and Au distribution of Lake Lefroy. This work provides a basis for future studies of the region in particular the variation of depositional sequences within regional paleochannel networks. 相似文献
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《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(10):855-860
In regolith-dominated terrains, the nature of contemporary processes and the surface distribution of regolith materials may be a poor guide to the character and history of regolith materials at depth. The nature of regolith materials at depth is often critical to unravelling the development of a landscape. Conventional mapping aids such as air photos, multispectral remote sensing and airborne radiometrics are not wholly adequate in this context, as they penetrate limited depths (<0.4 m). Airborne electromagnetics (AEM) on the other hand, has the potential to map regolith materials to considerable depths (>100m).The application of AEM to regolith mapping and its potential as a tool in geomorphology are illustrated by reference to an AEM survey flown at Lawlers in the Yilgarn Craton of Western Australia. At Lawlers, AEM identifies a palaeochannel that has no surface expression. It cannot be seen in images of the Landsat, airborne radiometric or airborne magnetic data. The disposition of this channel in the landscape, and in particular its association with ferruginous materials forming breakaways, suggest that inversion of relief has been a significant factor in the evolution of the Lawlers landscape.The AEM data at Lawlers have also been used to map the weathering front. The topography of the weathering front not only reflects the movement of water through the landscape in a general sense, but also reflects the influence of lithology and structure. Different lithologies are clearly weathering to different depths. Information on the nature of the weathering front is potentially an important constraint on models of groundwater flow, and by association, models of solute dispersion. 相似文献
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多龙矿集区控矿构造信息提取、识别与融合 总被引：1，自引：0，他引：1
西藏多龙矿集区近年来发现了大量的铜、金矿床,具有可观的资源潜力而倍受关注。通过对区内地质调查及矿产勘查数据的系统梳理与二次开发,利用基于分形理论的空间分析方法对该区成矿背景、构造格架等方面进行了深入细致的研究与探索。通过主成分分析方法,将水系沉积物地球化学数据中与斑岩铜金成矿相关元素和构造活动指示元素进行融合,并利用S-A(能谱-面积)模型对元素组合异常进行信息挖掘工作。结果表明,与区内构造格架相关的地球化学异常空间分布模式在指示矿化的同时,还对其与区域断裂构造之间的成生关系具有相当程度的指示意义。此外,区内开展的空间定量研究同时表明,S-A(能谱-面积)模型对描述由特定地质作用所造成的异常空间分布模式的自相似性有效,特别是针对地球化学背景模式的空间定量化描述,能更加深刻地刻画区内的构造格架并反映成矿背景。其结果推断了控制区内斑岩成矿系统的网格状断裂体系。此外,数据分析建模过程为在该区开展进一步的多元信息提取与融合提供了思路和借鉴经验,有利于找矿新靶区的发现与圈定。 相似文献
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Kolonodale矿床是东南亚红土镍矿带上一处典型矿床,位于印度尼西亚苏拉威西岛东部。矿床产自富镁超基性岩红土风化壳,矿化剖面自上而下出现红土层→腐岩层→基岩层垂向分带。红土镍矿石产在红土剖面上部,载镍矿物是铁质氧化物。硅镁镍矿石产在红土剖面中下部,载镍矿物为镍蛇纹石、镍滑石等含水层状硅酸盐矿物。地球化学分析显示,沿矿化剖面元素地球化学分异非常显著,Ni次生富集效应明显。超基性岩红土化过程的元素地球化学行为具有多样性,Fe、Al、Ti、Cr属残留富集组分,Si、Mg属淋滤缺失组分,Mn、Ca、Co、Ni属次生富集组分。通过典型矿床对比,Kolonodale矿床属原地自生硅酸盐型红土镍矿床,其发育受地质背景和地表环境条件的综合制约。富镁超基性岩、良好的构造组合、稳定的大地构造环境、湿热热带雨林气候、有利地形地貌等均是成矿有利条件。综合分析认为,Kolonodale矿床的成矿过程可划分为腐岩化、红土化和次生富集3个成矿阶段。 相似文献
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Kolonodale矿床是东南亚红土镍矿带上一处典型矿床,位于印度尼西亚苏拉威西岛东部。矿床产自富镁超基性岩红土风化壳,矿化剖面自上而下出现红土层→腐岩层→基岩层垂向分带。红土镍矿石产在红土剖面上部,载镍矿物是铁质氧化物。硅镁镍矿石产在红土剖面中下部,载镍矿物为镍蛇纹石、镍滑石等含水层状硅酸盐矿物。地球化学分析显示,沿矿化剖面元素地球化学分异非常显著,Ni次生富集效应明显。超基性岩红土化过程的元素地球化学行为具有多样性,Fe、Al、Ti、Cr属残留富集组分,Si、Mg属淋滤缺失组分,Mn、Ca、Co、Ni属次生富集组分。通过典型矿床对比,Kolonodale矿床属原地自生硅酸盐型红土镍矿床,其发育受地质背景和地表环境条件的综合制约。富镁超基性岩、良好的构造组合、稳定的大地构造环境、湿热热带雨林气候、有利地形地貌等均是成矿有利条件。综合分析认为,Kolonodale矿床的成矿过程可划分为腐岩化、红土化和次生富集3个成矿阶段。 相似文献
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The 42 element, 1190 sample Mobile Metal Ion subset of the National Geochemical Survey of Australia database was used to develop and illustrate the concept of Degree of Geochemical Similarity of soil samples. Element concentrations were unified to parts per million units and log(10)-transformed. The degree of similarity of pairs of samples of known provenance in the Yilgarn Craton was obtained using least-squares linear regression analysis and demonstrated that the method successfully assessed the degree of similarity of soils related to granitoid and greenstone lithologies. Exploratory Data Analysis symbol maps of all remaining samples in the database against various reference samples were used to obtain correlation maps not only for granitoid- and greenstone-related soil types but also to distinguish between, for example, samples derived from marine vs regolith carbonate. Likewise, the distribution of soil samples having a geochemical fingerprint similar to mineralised provinces (e.g. Mount Isa) can be mapped, and this can be used as a first-order prospection tool. 相似文献
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铂族元素矿床地球化学勘查的战略和技术 总被引：11，自引：1，他引：11
最近10年，PGE地球化学勘查取得许多进展，在此对主要进展作一简短的评述。①通过对已知其它金属矿床的再认识和再评价，发现新类型PGE矿床；②通过对已知PGE矿床的地球化学勘查，发现新的找矿靶区；③在空白区通过PGE地球化学填图，发现规模巨大的PGE地球化学省或巨省，为寻找PGE矿床提供了直接的找矿信息。根据中国的具体情况提出了中国PGE地球化学勘查的战略目标是：采用迅速，掌握全局，逐步缩小靶区的找矿战略，力争用5-10a时间使PGE矿床找矿获得重大突破。部署工作应以西南Pt、Pd地球化学省、新-甘-青Pt 相似文献
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KANG Huan CHEN Yuelong XUE Guoliang ZHAO Junxiang ZHANG N ZHANG Yangyang 《《地质学报》英文版》2022,96(2):571-581
Identifying ore-induced geochemical anomalies at the surface that indicate concealed deposits in buried areas remains a significant challenge in geochemical exploration. In this study, in order to trace the source of the geochemical anomalies, systematic luminescence intensity analyses were conducted on quartz grains from the Quaternary regolith at the Hadatu sandstone-type uranium deposit in the Erenhot Basin. The optically stimulated luminescence (OSL) ages were much older than the depositional ages of the Quaternary regolith. Moreover, quartz OSL ages were closely related to both borehole grades and sampling depths. Thus, the abnormal mineral OSL ages from near-surface sediments were ultimately controlled by the sandstone-type uranium deposits. This is identical to the rapid changes of quartz OSL ages (0.063 ka/cm) and equivalent doses (0.19 Gy/cm) with depths in a given sampling site. The instantaneous soil radon concentration was positively correlated with the quartz OSL apparent age, indicating their ore-induced origin and, as a result, their effectiveness in the exploration of concealed uranium deposits. Other parameters, including mobile-state uranium and 210Po contents, were poorly correlated with quartz OSL ages and therefore should only be used with caution for geochemical exploration. This is the first time an attempt has been made to discriminate the ore-induced sources for different surface anomaly parameters, including instantaneous soil radon, mobile-state uranium and 210Po contents for concealed sandstone-type uranium deposits. 相似文献
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The southwestern region of Australia contains the Yilgarn Craton that has been exposed to subaerial weathering since mid-Proterozoic. The gently undulating landscape experienced lateritic weathering so that today variably dissected, deep in situ isovolumetrically weathered regolith is widespread. Imposition of a more arid climate since the Miocene with the cessation of effective external drainage has resulted in substantial geochemical modification of the highly porous regolith. This vast pore volume acts as a reservoir for complex solutions that may be highly saline, extremely acid to alkaline and reducing. Diverse precipitates have formed in the regolith including widespread occurrence of silcrete, calcrete, dolocrete, ferricrete and gypcrete together with localised occurrences of pyrite, alunite, jarosite, barite, halite and other salts. Clearing of bush land for agriculture in the 20th century increased recharge so that rising chemically active groundwaters are damaging farmland and infrastructure throughout the region. To cite this article: B. Gilkes et al., C. R. Geoscience 335 (2003). 相似文献
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通过对东天山地区野外地质调查、化探补缺采样及对不同时期1∶20万、1∶5万化探数据的收集,对东天山地区元素分布特征及与镍矿有关的Cu,Ni,Cr,Co元素在不同时期、不同岩石中的分布特征进行总结,并对图拉尔根、白鑫滩、路北铜镍矿床与不同尺度化探中的异常特征进行总结。区域化探圈定找矿远景区,化探普查寻找基性-超基性杂岩体,并对其含矿性进行评价,化探详查可直接圈定矿体。通过化探成果数据集成,对东天山地区开展了定量预测,镍预测资源量987×10~4t。指出东天山铜镍矿带具有寻找超大型铜镍矿的潜力。 相似文献
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不同尺度地球化学填图能否获得稳定的和可追索的地球化学模式,能否真实反映元素含量背景,是检验填图方法是否可行的重要依据。笔者选择印度尼西亚苏门答腊岛巴东—明古鲁地区热带雨林区为研究对象,对比该区1:100 万（1 个样/100 km2）和1:25 万（1 个样/4 km2）两种不同比例尺的地球化学采样所获得的地球化学数据和异常分布模式,发现二者获得的元素含量背景值和中位数非常接近,所圈定的地球化学省在形态和变化趋势上非常类似,浓集中心的位置几乎完全重合,证明低密度地球化学填图也能获得稳定的和可追溯的地球化学模式,认为该方法在热带雨林区也是适用的。低密度地球化学填图圈出的地球化学省基本涵盖了研究区大的矿床和花岗岩体,真实的反映了研究区元素的分布情况,在这些地球化学省内开展更大比例尺的地球化学填图工作,能进一步圈定局部异常直接找矿,降低企业勘查投资风险。 相似文献
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地球化学填图与地球化学块体的谱系分析——编号系统及谱系树图的自动绘制 总被引：2，自引：0，他引：2
中国的地球化学填图研究工作起步较早并发展成为在国际上具有明显优势的学科。在此基础上提出的地球化学块体理论通过一定的编号系统绘制谱系树图来追索某元素在块体内部逐步浓集成矿的轨迹。通过谱系树图可以发现不同级别的子块体之间的亲缘关系,研究它们在时间和空间上的分布规律,结合已发现矿床的信息,预测潜在矿床的分布及其储量,从而指导找矿工作。提出了一种全新的谱系编号系统并编制了在计算机上自动绘制谱系树图的软件,同时实现了与原有编号系统的一致,解决了长期以来谱系树图不能自动绘制的问题,为地球化学块体的研究提供了一个很好的工具。 相似文献
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西藏驱龙铜矿区及其外围找矿前景地球化学评价 总被引：1，自引：0，他引：1
西藏驱龙斑岩铜矿床的发现是近年我国地勘行业找铜工作的重大突破之一。在发现找矿线索、确定成矿类型和评价找矿前景的过程中,勘查地球化学起了举足轻重的作用。1∶20万区域化探异常圈定了Cu-Mo矿化的范围,异常追踪查证工作确定了Cu-Mo矿化类型和找矿的有利地段。通过测区系统的地球化学勘查工作,结合地质构造资料,认为驱龙地区存在典型的斑岩铜矿床地球化学异常模式,矿化体剥蚀程度很浅,是找寻以斑岩型Cu-Mo矿化为主的超大型铜钼矿床的良好远景区。 相似文献