共查询到20条相似文献，搜索用时 234 毫秒
1.
黑色页岩是富含有机质和硫化矿物的特殊沉积岩,但人们对其风化过程的元素活动性及矿物风化机制关注较少.为探讨不同地形位置的黑色页岩化学风化过程,采集了渝东北城口某山脊 (A)、近山顶 (B) 和沟谷 (C) 的下寒武统水井沱组黑色页岩风化剖面岩样,利用XRD、XRF和化学分析手段对采集样品的矿物成分、主量元素进行测定分析.元素和矿物的质量迁移系数 (τ) 和质量迁移通量 (Mj, flux) 的计算结果表明,黑色页岩风化过程中Ca、Mg和Na元素具有明显的贫化现象,近地表处存在Al元素的富集现象;矿物成分方面,黄铁矿和有机质氧化后形成的酸性水环境,造成方解石、白云石、斜长石等不稳定矿物溶解,并生成含水石膏、铁质氧化物、黏土矿物等次生矿物.不同赋存位置的黑色页岩风化程度有所差异,Na/K-CIA、K/Ca*-Al/Na、A-CN-K和A-CNK-FM图解显示:A剖面处于脱Ca过程的初级风化阶段,B剖面处于脱Ca、Na初期的初等-中等风化阶段,C剖面已发生脱Ca、Na过程,并伴随脱Si作用的中等-强烈风化阶段,结合不同风化指数 (如:CIA、CIW、PIA、MWPI等),得出各剖面的化学风化强弱程度依次为C＞B＞A. 相似文献
2.
模拟不同气候条件下碳酸盐岩风化作用的淋溶实验研究 总被引：3，自引：3，他引：0
通过模拟干热、湿热与干冷3种气候条件,以饱和CO2水作为淋溶液,对黔中岩溶区3条碳酸盐岩风化壳岩-土界面的岩粉层试样进行了淋溶实验(其中干热、湿热条件下淋溶到残余酸不溶物阶段),对淋出液的pH值以及主要造岩元素的浓度进行了动态分析。结果表明,碳酸盐岩风化壳岩-土界面由岩到土的转变过程中,伴随碳酸盐的溶蚀,酸不溶物已表现出明显的风化倾向。碳酸盐的溶蚀强度表现为干冷>干热>湿热的变化趋势。温度低,碳酸盐的溶解速率大;排水条件好,碳酸盐溶解释放的Ca、Mg易随风化流体排出体系。对于酸不溶物组分,淋溶实验中有:(1)K、Na、Mg、Si、P的载体矿物风化强度在干热条件下最大(至于Ca,由于方解石与白云石均是其主要的载体矿物,酸不溶物相中的Ca难以在淋出液中有效识别)。在干冷与湿热之间,K、Na、Mg等盐基离子的溶出能力大多表现为湿热>干冷,指示了温度对盐基离子释放强度的重要制约作用;而Si和P未表现出一致的变化趋势,可能源于淋溶体系微环境的差异。(2)Fe与Mn表现出弱迁移性。其中,Fe在干冷环境下淋出强度最弱,说明温度是制约含Fe矿物分解速率的重要因素。而Fe在干热与湿热之间,以及Mn在3种淋溶条件下,未呈现出一致的变化趋势。(3)Al和Ti在碳酸盐岩风化过程中表现出强烈的惰性。 相似文献
3.
An analytical and experimental study of zoning in plagioclase 总被引：1，自引：0，他引：1
A detailed electron microprobe study has been conducted on natural and experimentally grown zoned plagioclase feldspars. Discontinuous, sector, and oscillatory chemical zoning are observed superimposed on continuous normal or reverse zoning trends. The relative accuracy of 3 element (Na, Ca, K) microprobe traverses was found statistically to be 2 mole percent. Comparison of microprobe data on natural zoned plagioclase with zoned plagioclase grown in controlled experiments has shown that it may be possible to distinguish zonal development resulting from physio-chemical changes to the bulk magma from zoning related to local kinetic control on the growth of individual crystals. 相似文献
4.
火山喷发的多期性是导致凝灰岩潜山纵向多期风化壳(带)发育的重要原因。从地球化学、测井响应特征和岩石学 证实了二连盆地凝灰岩潜山多期风化壳(带)的存在及其特征:(1)哈31井凝灰岩地层在1062~1080 m和1165~1179 m两 个井段表现为 K,Na,Ca 等元素淋滤,CIA 指数较大,而 Al,Fe,Mn,P 等元素相对富集,S/A 指数变小;(2)这两个层段 测井响应表现为风化壳的特征,而且其测井曲线在纵向上具旋回特征并有连井上的可对比性;(3)不同喷发期次形成的凝 灰岩结构、组分以及粒度不同。凝灰岩潜山多期风化壳(带)的存在对潜山油气藏的形成具有重要作用,成藏效应主要表 现在储集层垂向分带性、风化壳油藏(晚期风化壳中)和内幕油藏(早期风化壳中)纵向叠置和复式油气聚集成藏模式等 3 个方面。文中对多期凝灰岩古风化壳的认识扩展了火山岩潜山的勘探深度,为火山岩潜山内幕油气勘探提供了理论依据。 相似文献
5.
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
6.
本区富钾火山岩中浅色矿物有碱性长石、白榴石和霞石。碱性长石主要为钠透长石、钙歪长石,少数为钙钠透长石和歪长石,其光性变化与长石的地质时代和长石内部的隐条纹结构有关。白榴石的成分及产出方式主要与岩石中的SiO_2含量有关,SiO_2不饱和程度大的白榴苦橄岩的白榴石贫SiO_2;而SiO_2不饱和程度低的白榴碧玄岩和白榴玄武岩中,白榴石富SiO_2而稍贫K_2O+Na_2O,仅见于过渡相,而中心相由于水压较高和近于平衡的结晶条件,白榴石不能晶出,或先晶出后又与熔体反应形成碱性长石。 相似文献
7.
Art F White 《Geochimica et cosmochimica acta》1983,47(4):805-815
The weathering rates and mechanisms of three types of glassy rocks were investigated experimentally at 25 °C, pH 1.0 to 6.2, and reaction times as much as to 3 months. Changes in major element chemistry were monitored concurrently as a function of time in the aqueous solution and within the near surface region of the glass. Leach profiles, obtained by a HF leaching technique, displayed near-surface zones depleted in major cations. These zones increased in depth with increasing time and decreasing pH of reactions. Release rates into the aqueous solution were parabolic for Na and K and linear for Si and Al. A coupled weathering model, involving surface dissolution with concurrent diffusion of Na, K, and Al, produced a mass balance between the aqueous and glass phases. Steady state conditions are reached at pH 1.0 after approximately 3 weeks of reaction. Steady-state is not reached even after 3 months at pH 6.2.An interdiffusion model describes observed changes in Na diffusion profiles for perlite at pH 1.0. The calculated Na self-diffusion coefficient of 5 × 10?19 cm2·s?1 at 25°C approximates coefficients extrapolated from previously reported high temperature data for obsidian. The self-diffusion coefficient for H3O+, 1.2 × 10?20 cm2·s?1, is similar to measured rates of water diffusion during hydration of obsidian to form perlite. 相似文献
8.
《Applied Geochemistry》1994,9(2):119-125
Uptake of K, Ca, Mg and Na by vegetation in two upland ecosystems, one situated in andesitic parent material and the other on mica-schists, has been studied in relation to the mineralogy of the soils and the rates of weathering of base cations. Rates of weathering were calculated by two methods: (1) long-term rates were calculated from losses of the elements in soil horizons using Zr as an internal index; (2) current rates were calculated from input-output budgets using rain-water and stream chemistry over a 3 a period. Vegetation uptake can be related in a general way to mineralogy and weathering trends. Most of the K released from the soil appears to be taken up by the vegetation and the content of K in grass-dominated plant communities is related mainly to the availability of K from the weathering of mica. High levels of Ca in the streams indicate an overabundance of Ca which is being released mainly by weathering of plagioclase feldspar. Amounts of Mg in the vegetation are related to variations in the content of chlorite which is easily weathered at both sites. 相似文献
9.
利用扫描电镜和能谱分析研究天池火山天文峰剖面全新世喷发物中长石表面硅膜的结构状态和化学组成,结果显示:天文峰剖面从顶部黑色浮岩向下到暗灰色浮岩中,长石表面发育有不同结构状态的硅膜.硅膜的结构特征有随火山喷发时代越早,长石颗粒表面硅膜越厚,结构越复杂;喷发时代越晚,长石颗粒表面硅膜越薄,其结构越简单的变化趋势,即长石表面... 相似文献
10.
玄武岩风化是大气CO2 的一个主要碳汇过程,气候条件是影响玄武岩风化和固碳速率的重要因素。该文选择中国东
部不同气候带的新生代玄武岩典型风化剖面,进行了粘土矿物和常量元素分析。结果显示,在内蒙古-海南岛的采样区间内,
随着气候条件由干冷向暖湿转化,风化剖面中粘土矿物组合呈现蒙脱石+ 伊利石+ 高岭石→蒙脱石+ 高岭石→高岭石+ 三水
铝石的转变。剖面中土壤元素得失状况也显示出相应的规律,由于存在粉尘输入与风化淋滤作用的综合影响,在干冷的内
蒙古地区,粉尘对于Ca,K,Na,Si 等元素的输入量大于这些元素的淋失量;在山东地区,Ca,K,Na 元素开始快速淋失,
大于粉尘的输入量;在苏皖地区,Si 元素的淋失量开始小于粉尘输入量;而在湿热的海南地区,风化作用强烈,Si显示出
大量淋失的特点,碱性元素几乎全部流失。根据元素的相对得失率和北方粉尘平均组分的校正,初步估算了研究区内玄武
岩风化对大气CO2 的消耗速率,其数值在5.37~181.00 t（km2·a）之间,与Dessert 等（2003）的研究结果大致相当。 相似文献
11.
Kaolinisation of granite in an urban environment 总被引：1，自引：0，他引：1
Nick Schiavon 《Environmental Geology》2007,52(2):399-407
Under natural acid and wet conditions, one of the main weathering processes affecting granitic rocks is the kaolinisation
of Na, Ca and K-feldspar minerals by H2O + CO2 attack. We here report the occurrence of authigenic kaolinite on the surface of an eighteenth century granitic monument covered
with sulphate-rich weathering patinas. We suggest that, in humid mesothermic climates, anthropogenically derived gaseous SO2 from air pollution is responsible for accelerated kaolinisation of feldspars in an urban environment; SO2 from air pollution thus plays a dual role in the weathering of silicate rocks being responsible for the well known sulphation
of Ca-bearing materials leading to the formation of sulphate salts such as gypsum as well as the weathering of feldspar minerals
to kaolinite. The kaolinisation reaction weakens the granite microfabric leading to enhanced decay of the building stone. 相似文献
12.
桦甸盆地位于敦密断裂带之上,是我国著名的古近纪含油页岩断陷盆地。其中桦甸组油页岩段发育厚层的泥岩沉积。长期以来对该段油页岩特征研究较多,但对其物源区特征和构造背景研究甚少。对油页岩段厚层泥岩进行系统的地球化学分析结果表明：泥岩中w(SiO2)整体较低,K2O/Na2O值较高(大于1),w（MgO+Fe2OT3）为3.91%~11.66%,Al2O3/（Na2O+K2O）为3.77~6.29,表明泥岩中含有一定的铁镁质组分和较多的稳定组分。微量元素PAAS标准化分配曲线显示不同样品之间元素富集、亏损趋势不一致,同时稀土元素标准化曲线呈现出稀土含量变化较大、轻稀土富集和明显Eu负异常,表明油页岩段沉积时期存在多个物源。泥岩风化蚀变指数为74~82,Th/U值多集中在4.65~6.07,表明泥岩源区经历了相对中等的风化作用。Th/Sc和Zr/Sc值表明泥岩基本受源岩成分控制。由源岩和构造背景判别图解,并结合前人研究资料得知:桦甸盆地油页岩段母岩主要来自于海西期和燕山期花岗岩以及少量的燕山期中酸性喷发岩;源岩形成于大陆边缘造山带,为大陆岛弧火山岩系。 相似文献
13.
Bo Peng Adam Piestrzynski Jadwiga Pieczonka Meilian Xiao Yaozhu Wang Shurong Xie Xiaoyan Tang Changxun Yu Zhi Song 《Environmental Geology》2007,52(7):1277-1296
The mineralogy and geochemistry of the waste rocks distributed at Taojiang Mn-ore deposit, central Hunan province, China,
were studied using X-ray powder diffraction (XRD), electron microprobe analysis (EMPA) fitted with energy dispersive spectrometer
(EDS) and inductively coupled plasma mass spectrum (atomic emission spectra) ICP-MS (AES), with the aim of predicting the
environmental impacts of weathering of the waste rocks. The mineralogical results from microscope observation and XRD and
EMPA studies show that the waste rock is composed of black shale and minor Mn carbonates. The oxidation of sulfide minerals
such as galena, pyrite and chalcopyrite is accompanied by decomposition of Mn carbonates and K-feldspar during exposure to
atmospheric O2. The geochemical characteristics of major, rare earth elements (REE) and trace elements of the waste rocks also show that
the waste rock can be divided into black shale and Mn carbonate, and both of them are currently under chemical weathering.
The major alkalies and alkaline elements (Ca, Mg, Na, K, Rb, Sr and Cs) and major elements (Fe, S and P) and heavy metals
(Sc, V, Cr, Th, U, Sn, Co, Ni, Cu, Zn, Pb, Mo, Cd, Sb, an Tl) are being released during weathering. The mobility of alkalis
and alkaline elements Ca, Mg, Na, K, Rb, Sr and Cs is controlled by decomposition of Mn carbonates. The dispersion of Cr,
Sc and Th (U) might be related to weathering of K-feldspar, and the release of the heavy metals Co, Ni, Cu, Zn, Pb, Mo, Cd
Sb and Tl is dominated by the breaking of sulfide minerals. The REE of the waste rocks and surrounding soils and the spidery
distribution patterns of heavy metals in the waste rocks, the surrounding soils and the surface waters show that weathering
of the waste rocks and bedrock might be the sources of heavy metal contamination for the surrounding soils and surface water
system for the mining area. This is predicted by the mass-balance calculation by using Zr as an immobile element. Therefore,
it is urgently necessary take measures to treat the waste rocks distributed throughout the area for the local environmental
protection. 相似文献
14.
15.
Carbonate commonly accumulates in weathering profiles developed on noncalcareous parent material under arid and semiarid climatic conditions. Such weathering profile types are widespread in Morocco, making it critical to know the sources of the calcium in order to understand the genesis of carbonate-rich soils. In this study, we use 87 Sr/86 Sr as a geochemical tracer of the Ca sources in weathering profiles developed on volcanic rocks (basalt, tuff, andesite and latite) in the Mediterranean coast of Morocco. The results show that the most of the Sr, and hence Ca, is of an external origin, derived from (i) sea-water for the profiles located near to the coast or (ii) sea-water plus Liassic carbonate outcropping in the catchment for the profiles more distant from the coastline. The contribution of the host rock is small, being less than 25%. The ratio of the Sr (Ca) from the parent material to that from the external sources is controlled by the degree of porosity developed in the profile. 相似文献
16.
17.
Chemical weathering in Luzon, Philippines from clay mineralogy and major-element geochemistry of river sediments 总被引：3，自引：0，他引：3
Zhifei Liu Yulong Zhao Christophe Colin Fernando P. Siringan Qiong Wu 《Applied Geochemistry》2009,24(11):2195-2205
Clay mineralogy and major-element geochemistry of 35 surface sediment samples collected in 21 major to moderate rivers of Luzon, Philippines are used to evaluate the present chemical weathering process. The clay mineral assemblage consists mainly of smectite (average 86%) with minor kaolinite (9%) and chlorite (5%) and very scarce illite (1%), and does not show strong island-wide differences. The major element results of both bulk and clay-fraction sediments indicate that the formation of clay minerals is accompanied by leaching of Ca and Na first and of Fe and Mn thereafter during the chemical weathering process. A low-moderate chemical weathering degree of bulk sediments and a moderate-intensive degree of clay-fraction sediments are obtained in Luzon rivers based on proxies of chemical index of alteration (CIA) and smectite crystallinity. It is suggested that the majority of andesitic–basaltic volcanic and sedimentary rocks along with the tectonically active geological setting and sub-tropical East Asian monsoon climate are responsible for the predominance of smectite in the clay mineral assemblage. 相似文献
18.
川西北中生代特提斯沉积物地球化学特征对陆源风化条件的指示意义 总被引：1，自引：0，他引：1
顾雪祥 《矿物岩石地球化学通报》1996,(1)
川西北中生代特提斯沉积物地球化学特征对陆源风化条件的指示意义顾雪祥（成都理工学院．成都６１００５９）关键词特提斯浊积岩，风化条件，元素分配型式，碱金属－碱土金属，化学变异指数地史时期的物源区现今许多已被剥蚀破坏，因而有关这类物源区的母岩性质、同化条件... 相似文献
19.
Martin R. Lee Mark E. Hodson Maureen MacKenzie Caroline L. Smith 《Geochimica et cosmochimica acta》2008,72(20):4962-4975
Our ability to identify thin non-stoichiometric and amorphous layers beneath mineral surfaces has been tested by undertaking X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) work on alkali feldspars from pH 1 dissolution experiments. The outcomes of this work were used to help interpret XPS and TEM results from alkali feldspars weathered for <10,000 years in soils overlying the Shap Granite (north-west England). The chemistry of effluent solutions indicates that silica-rich layers a few nanometers in thickness formed during the pH 1 experiments. These layers can be successfully identified by XPS and have lower Al/Si, Na/Si, K/Si and Ca/Si values than the outermost ∼9 nm of unweathered controls. Development of Al-Si non-stoichiometry is coupled with loss of crystal structure to produce amorphous layers that are identifiable by TEM where >∼2.5 nm thick, whereas the crystallinity of albite is retained despite leaching of Na to depths of tens to hundreds on nanometers. Integration of XPS data over the outermost 6-9 nm of naturally weathered Shap feldspars shows that they have stoichiometric Al/Si and K/Si ratios, which is consistent with findings of previous TEM work on the same material that they lack amorphous layers. There is some XPS evidence for loss of K from the outermost couple of nanometers of Shap orthoclase, and the possibility of leaching of Na from albite to greater depths cannot be excluded using the XPS or TEM results. This study demonstrates that the leached layer model, as formulated from laboratory experiments, is inapplicable to the weathering of alkali feldspars within acidic soils, which is an essentially stoichiometric reaction. 相似文献
20.
《Applied Geochemistry》2002,17(7):885-902
An ancient saprolite has developed on the Palaeoproterozoic granulite, granite gneiss and amphibolite bedrock of the Vuotso–Tankavaara area of central Finnish Lapland. The present day climatic regime in Finnish Lapland lies within the northern boreal zone and so the saprolite there can be regarded as fossil. Cores of saprolite were collected from 4 sections (42 samples) and analyzed chemically and mineralogically. In the study area, progressive weathering of the rocks has been marked by gradual enrichment in Al, Fe and Ti; and depletion of Na, K and Ca. The higher concentration of Fe(III) and water and reduced Na and Ca in weathered bedrock in the 4 sections are indicative of oxidation, hydration and leaching processes involved during weathering. The primary minerals in the saprolite are plagioclase feldspar, K-feldspar, quartz, garnet (almandine) and hornblende; the common secondary minerals are kaolinite, halloysite, and vermiculite in addition to minor amounts of sericite. Intense weathering is indicated by: (1) the presence of kaolinite and halloysite in 4 sections of different bedrock types, and (2) the comparatively lower SiO2/Al2O3 (wt.%) ratio (2.30) of weathered granulites (3 sections) as compared to fresh granulite (4.33) and that of weathered amphibolite (2.68) as compared to fresh amphibolite (3.56). In general, kaolinite and halloysite have formed through the weathering of feldspars, garnet, and biotite. Vermiculite is the most probable alteration product of biotite. The formation of kaolinite and halloysite in Finnish Lapland indicates wetter and warmer climatic conditions during the time of their formation than at present. The possible time for formation of the saprolite is early Cretaceous–early Tertiary into Middle Miocene. 相似文献