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1.
《Applied Geochemistry》2002,17(3):321-336
Mineralogical, petrographical, and geochemical studies of the weathering profile have been carried out at Omai Au mine, Guyana. The area is underlain by felsic to mafic volcanic and sedimentary rocks of the Barama-Mazaruni Supergroup, part of the Paleoproterozoic greenstone belts of the Guiana Shield. Tropical rainy climate has favoured extensive lateritization processes and formation of a deeply weathered regolith. The top of the weathering profile consists of lateritic gravel or is masked by the Pleistocene continental-deltaic Berbice Formation. Mineralogical composition of regolith consists mainly of kaolinite, goethite and quartz, and subordinately sericite, feldspar, hematite, pyrite, smectite, heavy minerals, and uncommon mineral phases (nacrite, ephesite, corrensite, guyanaite). A specific feature of the weathering profile at Omai is the preservation of fresh hydrothermal pyrite in the saprolith horizon. Chemical changes during the weathering processes depend on various physicochemical and structural parameters. Consequently, the depth should not be the principal criterion for comparison purposes of the geochemical behavior within the weathering profile, but rather an index that measures the degree of supergene alteration that has affected each analyzed sample, independently of the depth of sampling. Thus, the mineralogical index of alteration (MIA) can provide more accurate information about the behavior of major and trace elements in regolith as opposed to unweathered bedrock. It can also aid in establishing a quantitative relationship between intensity of weathering and mobility (leaching or accumulation) of each element in each analyzed sample. At Omai, some major and trace elements that are commonly considered as immobile (ex: TiO2, Zr, etc.) during weathering could become mobile in several rock types and cannot be used to calculate the mass and volume balance. In addition, due to higher “immobile element” ratios, the weathered felsic volcanic rocks plotted in identification diagrams are shifted towards more mafic rock types and a negative adjustment of ∼20 units is necessary for correct classification. In contrast, these elements could aid in defining the material source in sedimentary rocks affected by weathering. Generally, the rare-earth element (REE) patterns of the bedrock are preserved in the saprolith horizon. This can represent a potentially useful tool for geochemical exploration in tropical terrains. Strong negative Ce and Tb anomalies are displayed by weathered pillowed andesites, which are explained by the influence of the water/rock ratio. 相似文献
2.
The regolith in the Mt Isa region of Queensland consists of a variety of saprolites and duricrusts developed on Proterozoic basement rocks and fresh to weathered Mesozoic, Tertiary and Quaternary cover, all of which has impeded base metals exploration. This paper presents an overview of some of the regolith-geochemical work conducted in the Mt Isa region as part of an industry-supported three year CRC LEME/AMIRA Project. A complex weathering and landscape history has produced a landscape of (a) continuously exposed and exhumed basement rocks that have undergone varying intensities of weathering and partial stripping; (b) weathered and locally eroded Mesozoic cover sequences and (c) areas with younger transported cover concealing basement and Mesozoic cover. Various regolith sample media have been evaluated at a number of prospects and deposits which represent different regolith-landform terrains and landscape history. Geochemical dispersion processes and models are presented and false anomalies explained.Where ferruginous duricrust or ferruginous nodular gravel are preserved on weathered bedrock on an eroded plateau, they exhibit large (> 500 m) multi-element (As, Pb, Sb) dispersion haloes and are useful sampling media. Dispersion haloes in truncated profiles on weathered bedrock covered with colluvium are restricted, are limited to tens of metres from subcrop of the source, and contrast to the extensive anomalies in ferruginous duricrust and nodules. Geochemical exploration in covered areas depends on the possible presence of dispersion through the sediments or leakage along faults or fractures, but may be complicated by high metal backgrounds in the sediments themselves. Some of the most prominent anomalies occur in ferruginous materials and soils representing emergent residual terrain developed on Mesozoic sediments. These are largely due to weathering of sulfide mineralization that continued during submergence in a marine environment, with hydromorphic dispersion into the sediments as they accumulated. Multi-element (Cu, As, Zn, Sb, Au) anomalies occur in basal sediments and at the unconformity, due to a combination of clastic and hydromorphic dispersion and represent a useful sample target. Metal-rich horizons in weathered sediments, higher in the sequence, can also be targeted, particularly by specifically sampling ferruginous units and fragments. However, these are less certainly related to mineralization. Zinc and Cu, concentrated in Fe (and Mn) oxides at redox fronts, may be derived by leaching from the sediments with concentration in the sesquioxides, and be unrelated to any proximal basement mineralization. In all these regolith-dominated terrains, a clear understanding of local geomorphology, regolith framework, topography of unconformities and the origins of ferruginous materials is essential to sample medium selection and data interpretation. 相似文献
3.
Many etch-pits on olivine grains occur as a pair of cone-shaped pits sharing a base, which consequently appear as diamond-shaped etch-pits in cross-section. Quantitative image analysis of back-scattered electron images establishes empirical dimensions of olivine etch-pits in naturally weathered samples from Hawaii and North Carolina. Images of naturally etched olivine were acquired from polished thin-sections by scanning electron microscopy. An average cone-radius-to-height ratio (r:h) of 1.78 was determined for diamond-shaped cross-sections of etch-pits occurring in naturally weathered olivine grains, largely consistent with previous qualitative results. Olivine etch-pit shape as represented by r:h varies from slightly more than half the average value to slightly more than twice the average. Etch-pit shape does not appear to vary systematically with etch-pit size. 相似文献
4.
Petrographic, mineralogical and chemical analysis of naturally weathered equilibrated ordinary chondrites collected from ‘ hot’ deserts and Antarctica has revealed striking similarities and also pronounced differences in weathering between the two environments. Terrestrial weathering in all meteorites studied is dominated by oxidation and hydration of Fe,Ni metal, producing Fe-oxides and oxyhydroxides that have partially replaced the metal grains and have also occluded primary intergranular pores to form veins. Troilite weathers readily in ‘ hot’ desert environments but undergoes very little alteration under Antarctic conditions. Most of the primary porosity of ordinary chondrites has been occluded by the time that ∼ 15 to 25% of the initial Fe0 and Fe2+ has been oxidised to Fe3+ in both environments. Results from modelling the volume changes upon alteration of primary minerals to a range of weathering products demonstrates that the primary porosity of most meteorites is sufficient to accommodate weathering products. Dilation of primary pores and brecciation, which has been observed in parts of some meteorites, will only occur if the meteorite is especially metal-rich, or has a low primary porosity. These weathering products are absent from recent falls but have formed in a fall after ∼ 100 yr of museum storage.Cl-bearing akaganéite and hibbingite are common weathering products in Antarctic finds but occur in abundance in only one ‘ hot’ desert meteorite, Daraj 014. The majority of Fe-rich weathering products in meteorites from both environments contain low, but variable concentrations of Si, Mg and Ca. In most meteorites a proportion of these elements are inferred to be present as a very finely crystalline mineral with a ∼ 1.0-nm lattice fringe spacing; where seen within intragranular fractures this mineral has a topotactic relationship with olivine and orthopyroxene. In the heavily-weathered Antarctic finds ALHA 78045 and 77002, Si is concentrated in cronstedtite, a Fe-rich phyllosilicate. An unidentified hydrous Si-Fe-Ni-Mg mineral or gel has also partially replaced taenite in ALHA 78045. In addition to Fe-rich weathering products, ‘ hot’ desert meteorites contain sulphates, Ca-carbonate and silica, whereas such minerals are largely absent from Antarctic finds. The abundance of silicate weathering products in Antarctic meteorites is unexpected and indicates that olivine and pyroxene undergo significant chemical weathering in these environments. As preterrestrial cronstedtite is abundant in CM2 carbonaceous chondrites, the Antarctic environment may be a powerful analog for aqueous alteration in the asteroidal parent bodies of primitive meteorites. 相似文献
5.
准噶尔盆地滴西地区石炭系火山岩储集性能分布规律研究 总被引：1，自引：0，他引：1
火山岩储集性能分布的非均质性非常强,探索其分布规律成为火山岩油气勘探的难点和重要任务。本文以实际岩心及其分析化验等资料为基础,从滴西地区取心最佳储集性能段、最差储集性能段、风化壳储集性能分布模式、薄层熔岩储集性能分布模式、厚层熔岩储集性能分布模式等方面总结了石炭系火山岩储集性能的垂向分布规律,同时分析了储集性能的平面分布情况。火山熔岩储集性能在垂向上的分布差异,成岩阶段主要受岩相的影响,后期主要受构造作用及风化溶蚀作用等的影响。受成岩阶段岩相的影响,溢流相上部亚相和下部亚相均有可能形成较好的储集性能。与碎屑岩互层的薄层熔岩常具有较好的储集性能。与碎屑岩互层的厚层熔岩段的底部储集性能可能较好,其次是顶部,而中部常沦落为储集性能相对较差的位置。风化壳的风化粘土层、强风化带、中等风化带、弱风化带、未风化带5个垂向分带结构中,中等风化带往往具备相对最佳的储集条件。应用W风化指数新型工具对火山岩进行风化程度评估显示,准噶尔盆地火山岩具有多期风化的特征,并残留有大量未风化、轻微风化及中等风化的火山岩,这其中不乏储集性能优良的岩性段。从平面分布来看,研究区域火山岩储集性能具有强烈的各向异性特征,常表现为局部富集,快速变迁,随机分布。 相似文献
6.
准噶尔盆地西北缘石炭—二叠系火山岩裂缝十分发育, 普遍充填方解石矿物。通过对钻井岩心裂缝类型划分、 方解石脉原生流体包裹体均一温度测试、 方解石地球化学数据测试与分析, 揭示了方解石脉成因。结果表明, 石炭—二叠系火山岩中的裂缝主要包括风化裂缝、 构造裂缝、 成岩裂缝和溶蚀裂缝。裂缝中方解石的原生流体包裹体均一温度分布为40℃～150℃, 变化范围较大, 具有低温、 高温及混合流体特征。方解石的碳、 氧同位素表明, 方解石的形成与大气淡水和埋藏流体有关, 锶同位素和锰元素进一步证实, 埋藏流体为深部热液流体或埋藏流体溶蚀了火山物质。准噶尔盆地西北缘石炭—二叠系火山岩受逆冲推覆构造和风化淋滤作用双重影响, 构造裂缝和风化裂缝彼此连通并沟通了深部热液与大气淡水。在火山岩裂缝中形成了兼具大气淡水与深部热液流体特征的方解石充填物。 相似文献
7.
Etch and intracutaneous landforms and their implications 总被引：1，自引：0，他引：1
C. R. Twidale 《Australian Journal of Earth Sciences》2013,60(3):367-386
Many landforms, major and minor, and including plains of various types, inselbergs, boulders, flared slopes, Rillen and rock basins, are initiated beneath the land surface, at the weathering front. They have evolved in various lithological settings. Most are formed by differential moisture attack, either controlled, or strongly influenced, by bedrock structure. Such forms of subsurface derivation may be differentiated into etch or subcutaneous features that were initiated at the base of the regolith, and intracutaneous forms that had their origin within the weathering zone. Although the agent or agents responsible for eroding the regolith and exposing the bedrock forms have varied in space and time, the similarity of etch and intracutaneous forms is such that their basic morphology persists regardless of the climatic regime in which they now occur. As the regolith is widely developed on the land surface, the forms initiated beneath and within it cannot be taken as climatic indicators. Indeed, like structural forms, these convergent forms represent a varied but significant azonal element in the physiographic landscape. 相似文献
8.
J.A. Hallberg 《Journal of Geochemical Exploration》1984,20(1):1-8
A technique employing Ti, Zr and Cr to aid in the identification of primary igneous rock type in deeply weathered situations is described. The method is based on Ti/Zr ratio which is little affected either by primary alteration or weathering and adequately defines compositional fields for major igneous rock types. For volcanic rocks Ti/Zr ratios are rhyolite <4< dacite <12< andesite <60< basalt. Ultramafic rocks cannot be discriminated from mafic rocks by Ti/Zr ratio but are generally distinguished by high Cr. 相似文献
9.
Quaternary alkaline basalts of Middle Atlas, are weathered into spheroidal volumes organized into weathering cover. In the profile studied, the study of transformations from a fresh core basalt to the most weathered rinds, has been analysed using BESI images (backscattred electron image analysis). A part from the microscopic analysis of each weatherted basalt, proportions of primary minerals, clays and pore space has been quantified in different stages of weathering. Indeed, in fresh core basalt, weathering is characterized by a first dissolution of the glass, followed by feldspar transformations in twinning plans, cleavages and in micropores inherited from the magmatic and cristallographic history of the rock.
In most basaltic weathered rinds, pore spaces given by the dissolution of the glass, were filled by a mixture of clays and iron products. In these samples, feldspars are completely dissolved giving important porosity occupied by small quantity of halloysite and kaolinite. The olivine and pyroxene transformations are accompanied by weak pore space formation. At the bottom of the soil, this porosity decreases in response to filling by later secondary products which come from the upper part of the soil by weathering solutions. 相似文献
10.
提要：岩石化学风化程度评价指标应该同时满足以下三个基本条件,即与风化程度之间的关系简单明确、对风化程度变化具有足够的敏感性和易于确定和不易受到人为因素影响。作为铁镁质岩石的主要代表,（峨眉山）玄武岩风化程度评价除考虑可引起组分淋失与富集的水解反应外,还应充分考虑二价铁的氧化反应。新鲜峨眉山玄武岩中并存的二价铁和三价铁的含量总体稳定,910个样品的FeO、Fe2O3平均含量分别为8.45%和5.15%,以均匀、随机的方式赋存于辉石、橄榄石、杏仁体中的绿泥石、磁铁矿及火山玻璃中。风化玄武岩、玄武岩斜坡地下水及新鲜玄武岩浸泡液的地球化学研究结果表明,FeO及Fe2O3含量对峨眉山玄武岩风化程度的敏感性明显高于其他组分,同时铁又是玄武岩风化过程中活动性最差的元素之一。三价铁和二价铁的摩尔数比值（FF）适合于峨眉山玄武岩整个风化过程的风化程度判别,比既有风化指数具有更高的分辨率,尤其是对风化初期玄武岩。 相似文献
11.
Chemical and physical weathering of primary minerals during the formation of laterite profiles in the Darling Range has formed distinct secondary mineral and morphological zones in the regolith. Erosion and human activity such as mining have exposed large areas of lateritic regolith, and its classification is important for land management, especially for mine rehabilitation. Preserved rock fabrics within regolith may enable the identification of parent rock type and degree of weathering, thus providing explanations for variations in important physical properties such as the strength and water retention of regolith. Feldspar, quartz, biotite and muscovite in porphyritic and fine-grained monzogranite in lateritic profiles have weathered via a series of gradational changes to form saprolite and pedolith consisting of kaolin, quartz, iron oxides, muscovite and gibbsite. Local reorganisation in the upper regolith or pedoplasmation zone has included illuviation of kaolin, which may be iron oxide-stained and which has disrupted the preserved rock fabric of saprock and saprolite. Quartz grain- or matrix-supported fabrics have developed, with greater pedoplasmation resulting in a quartz-grain-supported fabric. The recognition of these processes enables the use of gibbsite grainsize and distribution in regolith to infer original feldspar grainsize. Muscovite-rich or muscovite-deficient kaolin matrix indicates where plagioclase or alkali feldspar, respectively, was present in the parent rock. In some regolith, cementing by iron oxides has faithfully preserved rock fabric. The recognition of these various regolith types provides a basis for identifying the parent materials of lateritic regolith developed from granitic and doleritic rocks. Rock fabric is sometimes preserved in iron oxide-cemented bauxite mine floor regolith (Zh) due to the pseudomorphic gibbsite grains and iron oxide cement which forms a porous, rigid fabric. Plagioclase-rich granitoid is more likely to have weathered to dense clay-rich regolith (Zp), whereas albite and alkali feldspar have weathered to quartz-rich regolith (Zm) with the random orientation of quartz grains indicating that substantial reorganisation of rock fabric has occurred. It is possible to predict the response of regolith materials exposed in mine floors to management practices including ripping and re-vegetation, thus allowing targeted use of deep-ripping and planting density based on regolith type. 相似文献
12.
Preliminary geochemical study of volcanic rocks in the Pang Mayao area, Phrao, Chiang Mai, northern Thailand: tectonic setting of formation 总被引：1，自引：0，他引：1
Burapha Phajuy Yuenyong Panjasawatwong Pukpong Osataporn 《Journal of Asian Earth Sciences》2005,24(6):765-776
The least-altered, Permian mafic volcanic rocks from the Pang Mayao area, Phrao District, Chiang Mai Province, part of Chiang Rai–Chiang Mai volcanic belt, have been analyzed and are found to be mid-ocean ridge and ocean–island basalts. The mid-ocean ridge basalts occur as lava flows or dike rocks. They are equigranular, fine- to medium-grained and consist largely of plagioclase, clinopyroxene and olivine. These basalt samples are tholeiitic, and have compositions very similar to T-MORB from the region where the Du Toit Fracture Zone intersects the Southwest Indian Ridge. The ocean–island basalt occurs as pillow breccia, and lava flows or dike rocks. They are slightly to moderately porphyritic, with phenocrysts/microphenocrysts of clinopyroxene, olivine, plagioclase and/or Fe–Ti oxide. The groundmass is very fine-grained, and made up largely of felty plagioclase laths with subordinate clinopyroxene. These basalt samples are alkalic, and chemically analogous to those from Haleakala Volcano, Maui, Hawaiian Chain. These mafic volcanic rocks may have been formed in a major ocean basin rather than in a mature back-arc basin. 相似文献
13.
Mineralization with exchangeable rare earth element (REE) and yttrium (MEX-REY) has been recognized in the weathering profiles in South China since the early 1970's. This type of REY mineralization occurs in weathering profiles of parent rocks ranging in composition from granite to acidic volcanic rocks and lamprophyre. The majority of the known resources occurring in the weathering profiles of granitic rocks. Total resources of this type of REY amount to millions tons of rare earth oxides, and therefore represent one of the most important types of rare earth resources in China, particularly for heavy rare earth elements (HREE) and yttrium.Accumulation of REY in the weathering profiles of granitic rocks is strongly controlled by the resistance to weathering of the principal REY-bearing accessory minerals in the parent rocks; only a limited proportion of total REY (< 30%) is incorporated in the rock-forming minerals. MEX-REY more commonly occur in weathering profiles developed on granitic rocks within which most of the REY are incorporated in accessory minerals weakly resistant to weathering (doverite, parisite, etc.). For the well-developed weathering profiles, three horizons can be distinguished from surface downwards: the lateritic horizon (A), the weathered horizon (B), and the weathering front (C). Continuous leaching, coupled with low rate of denudation, results in the accumulation of REY in the subsurface horizons (the B and C horizons), and thus results in REE differentiation within the well-developed, layered, and mature weathering profiles. Exchangeable REY, which can be replaced by cations like NH4+ and Na+ etc. in electrolyte solutions and can be removed by complexing agents such as EDTA, are commonly the major form of REE occurrence in the B horizon. Cerium is enriched in the top layer (A horizon) and depleted in the subsurface horizons of the weathering profiles, most likely due to the oxidation of Ce(III) to Ce(IV) followed by cerianite formation or absorption onto clays and/or Fe and Al oxyhydroxides. 相似文献
14.
Prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations 总被引：18，自引：0，他引：18
The exposed crust consists mainly of plagioclase (35%), quartz (20%), K-feldspar (11%), volcanic glass (12%), biotite (8%), and muscovite (5%). Quartz is a resistate, thus feldspars and glass represent approximately 75 percent of the labile minerals. The weathering characteristics of these constituents are summarized in the context of thermodynamic, mass balance and kinetic considerations.Experimentally determined release rate constants were used to predict the proportions of Ca, Na and K released by feldspars of plutonic rocks (granites to gabbros) to weathering solutions. The chemical weathering trends of the weathered residues, calculated from the kinetic data, conform closely to the initial trends observed in some recent weathering profiles, demonstrating the accuracy of the predictions. Since the weathering of feldspars is controlled by processes that should not change through geological time, the relative release rates of Ca, Na, and K from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering.Experimentally determined release rate constants are not available for a wide range of volcanic glass compositions, but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks. The kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile. 相似文献
15.
Geochemical responses in weathered and oxidized surface metasedimentary rocks associated with stratiform lead-zinc mineralization at Stirling Hill (6 km west of Broken Hill) are compared with the geochemical responses in fresh drill core from an equivalent lithostratigraphic section with stratiform lead-zinc mineralization at the Pinnacles Mine (8 km south of Stirling Hill). Mineralization is interpreted as being volcanic exhalative and it lies within highly metamorphosed (sillimanite grade) rocks of the Willyama Supergroup.Surface rocks were classified into groups by discriminant analysis using drill core data from the Pinnacles Mine as the initial training set. The behaviour of elements in surface rocks varies with the rock group but Zn, Pb, Mn, Fe, and Co are leached from all surface rocks relative to fresh drill core.Nothwithstanding the leaching effects of weathering, common geochemical responses to mineralization have been identified in drill core and surface rocks. Coincident positive anomalies for Zn/Ba and Fe/(Na × Ba) ratios and negative anomalies for Na/(Mn × Ca) ratios uniquely define mineralization in both weathered surface rocks and in fresh drill core.The results demonstrate that the pattern of geochemical responses to Pinnacles-type stratiform volcanic-exhalative mineralization in surface rocks has survived the intensive weathering regime in the Broken Hill region. 相似文献
16.
硒是人和动物必需的微量元素,基于58件标准物质的化学风化指标和硒的认定值,采用微量元素地球化学背景值的经验方程形式拟合得到表征全国范围内硒背景值的经验方程：lgc=0822×(12-WIG/100)-1061×lg(K2O/SiO2)-2704,式中c为Se的含量(单位为μg/g),风化指标WIG的变化范围为43~1116,风化指标K2O/SiO2变化范围为0020~0137。该方程所表征的是样品因风化程度不同所呈现出的硒地球化学背景值,风化程度强的样品总体上具有较高的Se地球化学背景值。将该经验方程式在广东河台和广东南昆山两个研究区进行应用,认为寻找富硒区应当优先将风化程度较强的地区视为备选区,依据全国区域化探扫面数据可以方便地确定风化程度较强的地区。在环境质量评价中可以利用Se实测值确定足硒和富硒区,利用实测值扣除背景值获得的元素含量剩余值可以有效确定残积层土壤下伏的足硒和富硒岩石,即依据全国多目标地球化学调查数据可以有效地确定足硒和富硒地质体(残积层土壤及其下伏岩石)的分布区。广东南昆山岩体中西部的岩石应属于足硒和富硒地质体。 相似文献
17.
Shallow landslides (i.e., slide, flow, and complex) are widespread around the world, affecting the soil mantle and upper regolith as a result of the weathering of granitic bedrock, and periodically cause enormous social and economic damages. Shallow landslide hazards are predominantly due to the scarcity of warning signs during the pre-failure stage, high velocities reached in the post-failure phase, and an increase in mobilized volumes caused by the entrapment of material in the downhill path of the phenomena. Owing to the abovementioned aspects, susceptibility assessment of shallow landslides in weathered granitic rocks is a relevant issue for land use planning and design purposes. This study proposes a three-step methodology for the susceptibility assessment of these phenomena. The methodology has been tested and validated at the 1:10,000 scale over a 30.4-km2 area in southern Italy, where weathered granitic rocks are periodically affected by shallow landslides. This methodology is divided into three successive steps: step 1 consists of database creation, with an emphasis on the weathering grade map (including five weathering classes, from class II to class VI, each one characterized by comparable mechanical behavior), and steps 2 and 3 focus respectively on susceptibility map calibration and validation through statistical analyses. The area under the ROC curve (AUC) shows values ranging from 0.95 in step 2 (calibration) to 0.88 in step 3 (validation) and is a testament to the good overall predictive accuracy of the methodology. The obtained results demonstrate both the effectiveness and the consistency of the proposed methodology in performing susceptibility mapping of shallow landslides in weathered granitic rocks, as well as the important role played by the weathering grade map. 相似文献
18.
燕山中段 (主要是指北京市平谷县内 )大红峪组火山岩 ,在火山活动的间歇期 ,存在古风化现象。古风化使火山岩的成分、结构遭受改变 ,以致影响对岩石岩性的确定及同位素年龄的测定等。不同的地质环境 ,其风化情景不同。文中论述了火山岩的三种风化带及其不同的风化环境特征 ,并与现代风化带进行了对比。研究大红峪组的古风化现象 ,有利于更好地认识当时的地质环境。 相似文献
19.
火山岩风化壳储层发育模式——以三塘湖盆地马朗凹陷石炭系火山岩为例 总被引：4，自引：1，他引：3
中国的火山岩油气勘探近年来进展非常快,并不断在许多盆地发现了优质火山岩储层,其中风化壳型储层作为非常重要的火山岩储集体类型而倍受重视。三塘湖盆地马朗凹陷石炭系风化壳型储层储集空间以溶蚀孔洞缝为主,储层物性非常好。通过火山岩油气勘探中的野外露头观察、钻井取心、镜下薄片鉴定,及主量元素、微量元素等分析化验资料,并结合火山岩岩石学特征和物性特点,初步建立了该区的风化壳储层的发育模式,将火山岩风化壳储层在垂向上自上而下划分为五个带: ①最终分解产物带; ②水解带; ③淋滤带; ④崩解带; ⑤未风化带(母岩)。淋滤带储集物性最好,该区风化淋滤是改善储层的关键。 相似文献
20.
广西区内139个主要风化矿床(点)中有近4成集中分布于中酸性岩浆岩风化区。新近纪以来新构造运动活跃,东亚季风盛行产生了湿热气候,致使近2.0×105 km 2不同时代、不同岩性的中酸性岩浆岩广泛出露并遭受强烈风化,大面积的厚层风化壳在低山丘陵地貌景观区得以保存,这为风化矿床的发育提供了得天独厚的气候、地质、构造和地貌等条件。广西中酸性岩浆岩风化作用形成的矿床主要包括残积型(以钛铁砂矿为代表)、淋积型(以离子吸附型稀土矿为代表)和残余型(以高岭土矿和膨润土矿为代表)三个类型。这些不同类型的风化矿床在成矿条件上表现出显著的母岩专属性和风化环境偏在性,二者联合约束了风化矿床的成矿作用及成矿类型。风化过程中复杂的水岩反应(淋积作用、残积作用和残余作用)是导致中酸性岩浆岩风化形成各类矿床的内在机制。 相似文献