共查询到20条相似文献，搜索用时 234 毫秒
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常用化学风化指标诸如帕克风化指数（WIP）、化学蚀变指数（CIA）、成分变异指数（ICV）、CIX指数和αAlE常被用于评价源区化学风化强度,但利用以上化学风化指标评价化学风化强度时要考虑不同指标的控制因素,否则会导致风化评价结果失真。文章认为以最常用化学风化指标探究源区化学风化过程时,应在了解源区地质信息的情况下,选取合适的的细粒物质或悬浮物作为样品减弱粒度的控制作用,通过酸处理去除杂质,再利用Sc/Th-CIA 判别图反映物源信息,Th/Sc-Zr/Sc判别图进一步判别沉积分异和沉积再旋回的控制作用,进而选取ICV＞1的样品排除再旋回作用的干扰,用A-CN-K图或Panahi（2000）提出的公式进行钾交代作用的校正,最终通过CIA计算得出源岩化学风化强度。为确保准确反映源区风化情况,利用SPSS进行CIA受控因子分析,进而构建研究区的特征风化指标。 相似文献
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珙县恐龙化石埋藏地自流井组泥质岩地球化学特征及其对物源区和古风化作用的指示 总被引：1，自引：0，他引：1
四川珙县恐龙化石埋藏地是四川盆地早侏罗世重要的恐龙化石点,恐龙化石埋藏于下侏罗统自流井组之中。对该恐龙化石埋藏地自流井组泥质岩的常量元素、微量元素和稀土元素特征进行了研究,并根据其地球化学特征讨论了物源区性质、构造背景以及物源区的风化特征。常量元素和稀土元素表明其物源区以长英质岩石为主,构造背景为被动大陆边缘;反映化学风化程度的C IA指数及成分成熟度的ICV指数,表明物源区经历了较强的化学风化作用,反映了早侏罗世恐龙生活在一个温暖潮湿的古气候环境之中。 相似文献
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广元恐龙化石埋藏地是四川盆地中侏罗世重要的恐龙化石点,恐龙化石埋藏于中侏罗统沙溪庙组之中。笔者对该恐龙化石埋藏地沙溪庙组泥质岩的常量元素、微量元素和稀土元素特征进行了研究,并根据泥质岩的地球化学特征讨论了物源区性质、构造背景以及物源区的风化特征。主量元素和稀土元素表明其物源区以长英质岩石为主,构造背景为被动大陆边缘:指示化学风化程度的CIA指数及成分成熟度的ICV指数,表明物源区经历了中等的化学风化作用,反映了中侏罗世恐龙生活在半干旱的古气候环境之中。 相似文献
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利用化学蚀变指数法恢复物源区的风化历史及沉积物通量是一种经济实用、行之有效的方法。前人对珠江口盆地荔湾凹陷对应物源区的研究相对薄弱。本文通过对区内岩心测试数据进行化学蚀变指数分析,恢复晚渐新世—早中新世物源区的风化历史,并进行沉积物通量的估算,在此基础上探讨物源特征对研究区内沉积充填的控制作用。研究表明,晚渐新世研究区对应物源区经历了强烈风化阶段,该阶段产生的丰富的沉积物供给是研究区西北部快速进积、规模壮观的陆架边缘三角洲及斜坡重力流沉积体系发育的重要控制因素之一;早中新世,西北物源区风化减弱,沉积供给减少,但研究区东部沉积物供应较西部要充分得多,表明早中新世,研究区南部除了来自西北部的主要物源外,局部物源对该时期的沉积具有重要影响;推测东部物源(东部古隆起、兴宁古隆起)的突然复活是促进研究区东部早中新世沟槽形成发育的重要原因之一。在超深水区进行沉积物源区的研究中,这种半定量的方法对盆内局部物源的确定具有重要的指示意义。 相似文献
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本文对中侏罗统沙溪庙组泥质岩的主量元素、微量元素和稀土元素特征进行了研究,并讨论了物源区性质以及风化特征。物源区以长英质岩石为主,指示化学风化程度的CIA指数及成分成熟度的ICV指数,表明经历了低-中等的化学风化作用,反映了中侏罗世的半干旱气候环境。 相似文献
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物源分析方法及研究进展 总被引：149，自引：14，他引：149
物源分析是盆地和造山带研究的一项重要内容，它对分析沉积盆地与造山带的相对位置、演化过程及相互作用等方面意义重大。物源分析方法众多，中主要讨论了重矿物法、碎屑岩类法、裂变径迹法、沉积方法、地球化学和同位素法等的方法、原理及其应用条件和局限性，并指出地球化学方法和同位素方法具有广阔的应用前景。同时，也应该考虑构造抬升、剥蚀作用和化学风化等构造和沉积作用对物源区判定的影响。物源分析时应注意将多种方法相结合，扬长补短，才能得出合理的结论。 相似文献
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珠江口盆地阳江东凹处于太平洋构造域与新特提斯构造域交汇处,地球动力学背景、构造演化历史复杂,对于盆地物源特征和物源区古气候演化方面研究比较薄弱。选取珠江口盆地阳江东凹A钻井岩心中的珠海组-韩江组砂泥岩样品,对其进行地球化学分析,结果显示,样品呈轻稀土元素富集、重稀土元素平坦的配分模式,有明显的负Eu异常特征,与花岗岩相似;Al_2O_3/TiO_2、F1-F2、La/Th-Hf和Co/Th-La/Sc判别图解表明源岩以长英质为主,并有镁铁质岩石的混入;Al_2O_3/TiO_2、Cr/Zr和Th/Sc值也体现出长英质成分为主的物源特征;(Fe_2O_3+MgO)-TiO_2、Th-Co-Zr/10和Th-Sc-Zr/10构造环境判别图解显示,大部分样品落在大陆岛弧和主动大陆边缘区域,综合研究表明源区岩石特征与中国东南沿海大面积发育的岩浆岩极为相似。化学蚀变指数(CIA)、化学风化指数(CIW)、斜长石蚀变指数(PIA)等指标以及Mg/Ca值,指示珠江口盆地阳江东凹晚渐新世至中中新世物源区经历了中等程度的化学风化,对应温暖湿润的古气候环境,且从早到晚气温降低、降水量减少。 相似文献
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碎屑岩元素地球化学特征对沉积环境、物源属性和构造背景具有十分重要的指示意义。藏夏河组是分布于羌塘盆地北缘的一套砂泥不等厚互层的地层,其时代为晚三叠世卡尼期—诺利期,是古特提斯洋消亡阶段的沉积产物,其物源及构造背景分析对晚三叠世羌塘盆地演化过程探讨具有重要意义。本文选取岗盖日地区藏夏河组碎屑岩开展元素地球化学分析,通过碎屑岩物源属性及其构造背景研究,探讨晚三叠世羌塘盆地的演化过程及性质。研究区藏夏河组砂岩样品具有低—中等的化学蚀变指数CIA=55. 0~65. 9、化学风化指数CIW=60. 6~74. 3 和斜长石蚀变指数PIA=56. 1~70. 6,反映物源区总体发生了弱的化学风化作用。Al2O3/TiO2、TiO2/Zr、Cr/Th、Sc/Th、Co/Th、La/Sc 值和显著的Eu负异常,表明藏夏河组物源主要来自长英质岩石,同时可能含有少量安山质物源。多重构造判别图解表明物源区主要来自于活动大陆边缘和大陆岛弧,少量来自于被动大陆边缘物源区。结合前人研究资料,笔者等认为晚三叠世早期羌塘盆地具有弧后前陆盆地的特征,而藏夏河组形成于同造山期或者造山后。 相似文献
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LI Qiugen CHEN Xu LIU Shuwen WANG Zongqi ZHOU Yingkui ZHANG Jian WANG Tao 《《地质学报》英文版》2009,83(3):550-561
Abstract：In this study, whole-rock geochemical and Nd isotopic data, as well as detrital zircon Hf isotopes of Palaeoproterozoic metasedimentary rocks from the Jiangxian Group are presented to evaluate the characteristics of their provenance and the tectonic history. The major and trace element compositions are comparable to Post-Archean upper continental crust (PA-UCC), but have slight enrichment in the LILE, with the exception of Cs and Sr, and a slight depletion in ferromagnesian elements, HFS elements, such as Nb and Ta, and some major elements, such as CaO and Na2O. The geochemical data reveal that the collected metasedimentary rocks have experienced intermediate source weathering with chemical index of alteration values ranging from 72 to 78, varying degrees of K-metasomatism, and post-depositional loss of Na, as well as negligible sorting, and are derived from the weathering of mostly felsic and non-mafic rocks. The selected Lu–Hf isotopic analysis on detrital zircon points to both the Trans-North China Orogen and Eastern Block of the north China craton as the most likely sources for the metasedimentary rocks of the Jiangxian Group. However, a contribution of detritus from the Western Block of the north China craton can be ruled out. The sediments were probably deposited in a back-arc basin within an active continental margin setting. 相似文献
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Chemical processes affecting alkalis and alkaline earths during continental weathering 总被引：10，自引：0，他引：10
The alkali and alkaline earth concentrations in the Toorongo Granodiorite weathering profile are controlled by two competing processes; leaching of cations from primary minerals during their degradation to clays; fixation, by exchange and adsorption, of the same cations onto the secondary clay minerals. Degradation and leaching dominate the early weathering stages whereas during the advanced stages, exchange and adsorption onto clays are of most influence.The alkali and alkaline earth compositional changes in the Toorongo Granodiorite weathering profile are typical of changes occurring during weathering of the continents, consequently the following generalizations apply to continental weathering. Ca, Sr and Na are most rapidly and most strongly removed (as dissolved species) during weathering of fresh continental rocks. Although large quantities of Mg are transported to the marine environment as dissolved species, appreciable amounts remain (fixed in secondary clay minerals) at the weathering site to be removed during mass wasting of continental weathering profiles. Large quantities of Rb, Cs and Ba, fixed in continental weathering profiles by exchange and adsorption onto secondary clays, are transported from the continents only during mass wasting of the continents. 相似文献
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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
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柴西地区南翼山构造上新统混积岩中含有大量盐类矿物,其物源分析对盐矿物质来源研究有一定的参考价值。本文在野外观察和镜下鉴定的基础上,对南翼山构造上新统狮子沟组混积岩的地球化学特征进行了分析,并结合周缘造山带花岗岩的稀土元素数据,探讨了混积岩中陆源碎屑的物质来源。结果显示：南翼山构造狮子沟组混积岩中碎屑矿物、碳酸盐矿物和黏土矿物呈均匀混合的状态,元素含量与矿物组分密切相关,除Ca、Na、Sr元素外,其余元素含量普遍低于上地壳平均含量,其中CaO和Na2O受碳酸盐和石盐形成影响,不能用于判别构造背景,而Sc、Th、Zr、Hf等微量元素和稀土元素较完整地保留了源岩的地球化学信息,可用于源区构造背景的判别及物源示踪,同时稀土元素配分模式一致性较好,表明混积岩中陆源碎屑具有相同的物源特征。稀土元素配分模式、La Th Sc、Th Sc Zr/10、La/Th Hf图解以及Al2O3/TiO2比值共同指示南翼山混积岩的陆源碎屑组分来源于大陆岛弧背景下的长英质火成岩,通过与周缘造山带花岗岩稀土配分模式对比,推断晚志留世和晚二叠世花岗岩是混积岩中陆源碎屑和盐类矿物的主要源岩,南部的祁漫塔格是主要的物源区,且西部的阿尔金南段也有部分物源贡献。 相似文献
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Geochemistry and provenance of bed sediments of the large rivers in the Tibetan Plateau and Himalayan region 总被引：1，自引：0，他引：1
Weihua Wu Hongbo Zheng Shijun Xu Jiedong Yang Hongwei Yin 《International Journal of Earth Sciences》2012,101(5):1357-1370
We investigated the geochemical characteristics of major, trace and rare earth elements and Sr–Nd isotope patterns of bed sediments from the headwaters and upper reaches of the six large rivers draining the Tibetan Plateau (the Jinsha River—Yangtze, Lancang River—Mekong, Nujiang River—Salween, Huang He—Yellow, Indus, and Yarlung Tsangpo—Brahmaputra). By using Ca/Al versus Mg/Al, La/Sc versus Co/Th, and 87Sr/86Sr versus εNd (0) binary differentiation diagrams of provenance, some typical contributors to the different catchment sediments can be identified. In the Three-River (the Jinsha, Lancang, and Nujiang Rivers) tectonomagmatic belt, acidic–intermediate-acidic volcanic rocks are very important provenance of sediments. Carbonate rocks and Permian Emeishan basalts are dominant in the Jinsha River. The Yellow River sediments have similar geochemical characteristics with loess in catchments. The Indus and Yarlung Tsangpo Rivers sediments are mainly from ultra-K volcanic rocks and Cenozoic granitoids widely distributed in the Indus–Yarlung suture. The intensity of chemical weathering in these river catchments is evaluated by calculating the chemical indices of alteration (CIA) of sediments and comparing them with bedrocks. The CIA values of the six river sediments are from 46.5 to 69.6, closing to those of bedrocks in the corresponding catchment, which indicates relatively weak chemical weathering intensity. Lithology, climate, and topography affect the chemical weathering intensity in these river catchments. 相似文献
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对南堡凹陷馆陶组(粉)砂岩的主量、微量及稀土元素的地球化学特征研究表明：多数主量元素含量中等,SiO2、Al2O3等主元素含量及其相关比值反映大多数砂岩属于岩屑砂岩和长石砂岩,个别为杂砂岩;镁铁族元素(Co,Cr,Ni,Sc,V)和大离子亲石元素(Rb,Cs,Ba,Sr)含量类似于上地壳。砂岩十分相似的REE分布模式显示了相似的物源和构造背景。SiO2-K2O/Na2O图解、主元素双变量判别图解及Th-Sc-Zr/10和Th-Co-Zr/10等构造背景判别图解均表明,馆陶组物源区属于活动大陆边缘构造背景。根据主元素物源判别方程图、La/Sc-Co/Th和Th-Hf-Co图投影及(Gd/Yb)N值,表明馆陶组物源主要来自由长英质岩石组成的后太古宙上陆壳。通过与燕山地区不同时代(期)中酸性火山岩和花岗岩REE的对比,表明母岩主要来自燕山褶皱带地区于燕山期发育的中酸性火山岩和/或花岗岩体。 相似文献
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云南姚安碱性杂岩体的岩石学和地球化学特征 总被引：3，自引：1，他引：3
对云南省姚安碱性杂岩体的K-Ar年代学、岩石学、岩石化学、微量元素、稀土元素和Sr、Nd、Pb同位素组成等进行了综合研究表明(1)该碱性杂岩体的岩性从超基性、基性、中性到酸性;(2)各类型岩石化学成分均富碱(Na2O+K2O=6.6%~11.6%)、高钾(K2O/Na2O>1)和富钙(CaO=0.3%~12.5%);(3)微量元素富集Rb、Sr、Ba等大离子亲石元素(LILE),贫Zr、Nb、Ta等高场强元素(HFSE)。稀土元素富集LREE和正负铕异常不明显;(4)Sr、Nd、Pb同位素特征一致显示姚安碱性杂岩体的源区为EMⅡ型富集地幔,EMⅡ型地幔端元代表了与壳幔再循环相联系的交代成因富集地幔源;(5)岩体形成于陆内非造山的张性构造环境;(6)岩体的形成与古特提斯造山带的演化、印度大陆与欧亚大陆碰撞以及进而产生的强烈陆内变形及大尺度新生代走滑断裂这些大的构造事件无论在时间、空间和机制上都有着密切的耦合关系。 相似文献
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本文以塔里木盆地西北缘苏盖特布拉克组泥质岩为对象,对其进行了主微量元素和稀土元素地球化学分析测试,并据此探讨苏盖特布拉克组的古沉积环境、物源属性及古构造背景。结果表明,泥岩中的Al、Fe、K、Ti、Li、Sc、Th、U、Ga、Cu元素明显富集;轻稀土元素富集且分馏程度强烈,重稀土相对亏损,且具明显的Eu负异常;泥岩的化学蚀变指数为60~80,多数样品的成分变异指数大于1.0。研究表明,研究区泥质岩形成于温暖湿润的浅海氧化环境,水体盐度较低;泥质岩为初次旋回沉积物,经历了中-低程度的化学风化作用,其母岩主要为上地壳长英质岩石,并混入了少量的基性岩、碱性岩与古老沉积物;源区构造背景以大陆岛弧环境为主,兼有活动大陆边缘特征。 相似文献
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Major element compositions of 36 bulk samples and 41 clay samples, which were obtained from 47 topsoils collected in monsoonal eastern China, were investigated with conventional wet chemistry and X-ray fluorescence (XRF) spectrometry, respectively. Based on major element analyses, the mobility of major elements and latitudinal distributions of SiO2/Al2O3 ratio, chemical index of alteration (CIA), chemical index of weathering (CIW) and weathering index of Parker (WIP) were analyzed. Meanwhile, the suitability of these chemical weathering indices to topsoils in monsoonal eastern China and its controls were discussed.These investigations indicate that Na, K, Ca, Mg, and Si are relatively depleted, while Mn, P, Fe and Ti are relatively enriched in topsoils of the study area by comparison with their contents in the upper continent crust (UCC), and that alkali metal (Na, K) and alkaline earth metal (Ca, Mg) elements are generally easier to be depleted from their parent materials than other major elements during chemical weathering. The latitudinal distributions of CIA, CIW and WIP show that they are suitable to both bulk and clay samples, but SiO2/Al2O3 is only suitable to clay samples, not suitable in bulk ones. All these investigations indicate a significant dependence of grain-size in major element abundance and latitudinal distributions of SiO2/Al2O3, CIA, CIW and WIP, but parent rock type has little effect on them, except its impact on the latitudinal distribution of WIP in clay samples. The significant grain-size dependence probably indicates the presence of unaltered minerals in bulk samples, thus we suggest that clay samples are more suitable to investigating chemical weathering of sediments on continents than bulk samples. The trivial effect of parent rock type probably indicates a relatively uniform chemical weathering on various parent rocks. Correlation analyses indicate that climate is the dominant control of chemical weathering of topsoils in the study area, and the significant latitude effect indicated by the spatial distributions of chemical weathering indices actually reflect the climate control on chemical weathering of topsoils.Chemical weathering indices actually reflect the integrated weathering history in the study area. Besides the dominant control of climate, other factors like tectonics, parent rock, biology, landform and soil depth and age might also have some effect on the chemical weathering of topsoils in the study area, which needs further research. 相似文献