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单矿物地球化学分析是沉积物源分析研究的重要手段,运用广泛。沉积物中碎屑矿物的粒度组成,即水动力分选作用,是否影响到基于这种方法的物源解释,目前尚不清楚且受到的关注不多。通过研究柴达木盆地北缘地区第三系沉积物中的680颗碎屑石榴石(0.068~0.557 mm)的主量元素地球化学组成数据,解释了不同粒度的碎屑石榴石物源。结果显示,0.063~ 0.125 mm的碎屑石榴石的地球化学结果中Fe^2+与Mn^2+含量更高,表明其母岩的变质结晶程度较弱,故物源解释结果更可能为中—低级角闪岩相变沉积岩,而其他粒径的碎屑石榴石Ca^2+与Mg^2+含量更高,这说明其物源区的温压条件较前者高,因而物源解释结果为低级变质相,中酸性火成岩,榴辉岩等宽泛结果。这种碎屑石榴石粒度差异导致的地球化学组成的不同,说明碎屑石榴石的颗粒大小在一定程度上会影响物源解释结果。因此,在进行单矿物地球化学物源研究时,选取特定粒径(0.063~ 0.125 mm或0.125~ 0.25 mm)组成的碎屑矿物进行分析,可以消除水动力分选作用的影响,有助于获得更为准确的物源解释结果。 相似文献
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内蒙古索伦地区上二叠统林西组碎屑岩地球化学特征及其对物源的指示意义 总被引：2，自引：0，他引：2
内蒙古索伦地区上二叠统林西组沉积物源受控于晚古生代古亚洲洋的闭合事件。本文通过分析碎屑岩元素地球化学特征,对林西组母岩类型和古构造环境进行了探讨。常量元素分布特征表明,林西组早期属于风化程度较弱的第一次旋回沉积物,后期属于中等风化的第一次旋回沉积或再旋回沉积物,母岩类型以火成岩为主;微量元素和稀土元素分布特征表明,林西组母岩沉积环境为大陆岛弧背景下切割的岩浆弧,以上地壳碱性-中性火成岩为主,伴有钙质-泥质沉积岩,（Gd/Yb）n表明早期沉积母岩为太古宙碱性火成岩。综合分析表明,林西组沉积同时接受南侧华北板块北缘和北侧苏尼特左旗-锡林浩特-西乌旗南岩浆弧的共同物源供给,早期沉积有华北板块北缘太古宙基底母岩的参与。 相似文献
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本文通过对鄂尔多斯盆地镇原地区下白垩统砂岩进行主量元素、微量元素及稀土元素REE等地球化学分析, 就下白垩统砂岩的沉积再循坏特征、化学风化及其构造背景和物质来源等展开讨论。研究表明: ① 下白垩统洛河组、环河组和罗汉洞组的物源主体上具有相似性, 且在构造背景、物源区及物源特征上有良好的继承性。物源区总体具有富石英、富方解石胶结物、钾长石或富钾矿物较斜长石多的特点, 罗汉洞组较环河组和洛河组硅质更高、方解石胶结物更少、质更纯。稀土元素REE配分模式曲线一致, 轻重稀土分馏明显, 富集大离子亲石元素Ba、Pb、Sr和轻稀土元素, 亏损高场强元素Nb、Ta、Th、Y等,自下而上随着地层变新, 沉积岩中总的稀土含量有变小的趋势, 重稀土元素分馏程度减小; ② 研究区下白垩统砂岩原始物质主要为长英质与基性岩混合岩 (如中酸性侵入岩、长英质变质岩)及部分沉积岩。研究区大部分沉积物是鄂尔多斯盆地西南缘逆冲推覆带母岩风化剥蚀的产物搬运至此沉积形成, 系首次沉积的物质, 少数沉积物 (即风成砂)为就地再次搬运堆积形成, 系再循环沉积物质; ③ 在构造背景上具有以被动大陆边缘构造环境占主要优势的特点。碎屑物主要来源于陆块源区, 其次来源于再旋回造山带和混合源区。 相似文献
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大兴安岭北部漠河盆地内广泛发育二十二站组,其形成时代及物质来源一直以来备受争议.本文在野外地质调查及岩相学的基础上,利用碎屑锆石LA-ICP-MS U-Pb法测年,并结合岩石地球化学等方法,探讨了二十二站组形成时代、物源区大地构造环境及沉积物来源.测年结果显示132个测点年龄主要分布在4个群落,分别为508.3～492.3 Ma;486.9～435.5 Ma;278.3～254.2 Ma;209.5～178.1 Ma.本次获得二十二站组最小碎屑锆石年龄为178.1 Ma,并结合漠河盆地东西部碎屑锆石的年龄,综合认为二十二站组形成时代应为中晚侏罗世.地球化学分析结果显示,二十二站组砂岩的稀土元素与活动大陆边缘的稀土元素曲线吻合较好,且相对亏损高场强元素(Nb和Ta)和大离子亲石元素(Ba和Sr),相对富集高场强元素(La、Th、Zr、Hf),地球化学特征与活动大陆边缘相似.综合古流向、源区母岩分析、碎屑锆石测年分析、微量元素特征等诸多因素,本次研究认为本区二十二站组砂岩的母岩主要来源于盆地南缘广泛分布的前中生代沉积-变质基底(兴华渡口岩群、佳疙瘩组、额尔古纳河组等)及各期中酸性火成岩. 相似文献
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《矿物岩石地球化学通报》2015,(4)
为探讨云南者桑金矿床的成矿构造背景、成矿流体及物质来源,对与金矿化相关的岩矿石及石英脉进行了主、微量元素特征研究。研究表明,主量元素的K2O/Na2O-Si O2判别图解及F1-F2判别图解显示本区二叠系上统吴家坪组(P3w)地层构造背景处于被动大陆边缘,母岩物源区呈现由火成岩物源区向沉积物物源区演化的趋势。石英脉稀土元素特征指示本区成矿流体呈还原及弱酸性环境,成矿流体来源总体以壳源为主。岩矿石稀土元素特征表明成矿物质主要来源于富含有机质的吴家坪组含金岩石建造,金成矿晚于印支期基性岩浆活动,推测燕山期成矿更为合理。 相似文献
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为研究神农架后山坪地区古城组碳酸盐岩的地球化学特征及其成因和沉积环境,系统采集了该组样品并进行主、微量元素地球化学分析。结果显示,样品的TiO_2与SiO_2、Al_2O_3呈一定程度的正相关,与CaO、MgO呈负相关,说明古城组的沉积物来源可能为陆源沉积物和化学沉积物,主要为陆源沉积物;古城组沉积岩为水成沉积岩,非热水来源沉积,沉积物富火山碎屑或经历过钾交代变质作用;古城组沉积时为寒冷干燥、化学风化作用弱的古海洋氧化环境,地球化学参数指示,古城组沉积时期的氧化程度较比中元古代古海洋环境强,这与该时期所发育的冰期(古城冰期)有良好对应。 相似文献
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通过对川东南地区小河坝组砂岩的碎屑组分、岩屑类型、重矿物组合、地球化学（稀土元素、微量元素）及古流向的研究,分析了小河坝组砂岩的物源方向、母岩类型及源区的构造背景。结果显示：源区为盆地东边江南－雪峰山隆起西侧上元古界板板溪群及其侵入板溪群中的基性岩体、中基性喷出岩体。具有活动大陆边缘、大陆岛弧及被动大陆边缘的构造背景。地球化学研究进一步证明,母岩主要为更老的沉积岩再旋回沉积物及少量岩浆岩。在早志留世小河坝期以华南板块缓慢向扬子板块蠕动方式相拼接,致使扬子板块整体缓慢抬升,同时沉积中心不断向西北方向迁移,造成研究区具有明显沉积旋回性的物源供给特征。 相似文献
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辽宁营口后仙峪硼矿区的超镁橄榄岩是该区硼镁石型硼矿的主要赋存岩石,其地质地球化学特征是①超镁橄榄岩呈带状、透镜体状分布,它整合于古元古代的火山-沉积岩系中的含硼岩系富镁硼酸盐岩组中.岩石几乎由镁橄榄石组成,具有变余的火山沉积的组构.②主量元素说明岩石化学成分具富镁、富铁的特点.③非活动性微量元素较高,如Zr、Hf、Ta等,与一般超基性岩相似;Cr、Ni含量低,显示岩浆为非原始岩浆;Nb*大于1以及(La/Yb)N-(Yb)N图解均说明岩石的幔源性.④稀土元素总量为7.41×10-6～46.82×10-6,与上地幔相当,轻、重稀土分馏不太明显,负Eu异常明显,具有与纯橄榄岩一致的"V"型稀土元素分布模式.⑤ε Nd为-7.51961～9.0654,亦反映出壳幔混染的特点.由地质地球化学特征可以推测岩石为经过地壳混染的地幔橄榄岩较大程度部分熔融后而残留的富镁岩石. 相似文献
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西秦岭下拉地超基性岩体的地球化学特征及构造意义 总被引：1，自引：0，他引：1
系统研究了西秦岭下拉地超基性岩的地质与地球化学特征,结果表明:下拉地超基性岩具有低SiO2、富Mg和贫碱特点;变质原岩主要属于橄榄岩类;不同岩石类型之间微量元素及稀土元素的分布具有一定差异;下拉地岩体的原生超基性岩岩浆主要起源于上地幔,成因类型属于俯冲带地幔橄榄岩;岩浆演化过程中受到壳源物质的加入和海相碳酸盐物质的加入,造成下拉地超基性岩高Al2O3、高CaO的特殊地球化学组成特点。笔者对由于蚀变作用影响形成的地球化学特征的原因进行了初步探讨。 相似文献
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碎屑重矿物分析对库车坳陷白垩—第三纪物源变化的指示 总被引：12，自引：1，他引：12
碎屑沉积是山脉隆升和盆地沉积的直接记录，包括碎屑重矿物研究在内的碎屑沉积物的分析是开展盆山耦合研究的必要手段。对库车坳陷白垩系—第三系砂岩中重矿物含量特征进行了系统的研究，并应用电子探针技术分析碎屑石榴石和钛铁矿的化学组成，研究表明库车坳陷白垩—第三系源区主要由沉积岩、变质岩和酸性火山岩组成。白垩系砂岩中的石榴石来自西南天山蓝片岩和低级变质岩的比例较大，而第三系砂岩中的石榴石中富铁铝榴石组分，多来自高级变质岩。白垩系砂岩中的钛铁矿多来自变质岩，上第三系砂岩中来自火成岩的钛铁矿比例增加。由此可以认为南天山的大规模隆升和剥蚀发生在第三纪以来，由于它的隆升遮挡了南天山北缘古生代增生杂岩体对库车坳陷的物质贡献，并且随着剥蚀的加深，高级变质岩和火成岩的出露越来越多。 相似文献
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In situ analysis of detrital apatite is a significant approach to sedimentary provenance analysis, which is an important aspect in sedimentary geology study. Several trace elements such as Sr, Y and Rare Earth Elements (REEs) concentrate in apatites, and the distribution of these elements depends on the content of SiO2 and the distribution coefficient of the melt, thus the trace element abundances is obviously different in different rocks. These features can be used to indicate parent-rocks of detrital apatites in sedimentary rocks. The approaches and proxies of detrital apatite to sedimentary provenance analysis can be summarized as follows. ①elemental geochemistry, such as Sr, Y, REEs, the approaches including chondrite-normalised REE distribution patterns of apatites, Classification and Regression Tree (CART) and discriminant plots of REE parameters; ②isotopic geochemistry, including Sr-Nd and Lu-Hf isotopes; ③Multi-dating, including low-temperature thermochronology such as (U-Th)/He (AHe)and Fission Track (AFT) dating, and high-temperature thermochronology such as U-Pb dating. Based on an integrated analysis using these methods, we can get various and comprehensive geological information such as the rock type, formation conditions and evolution of source rocks, the history of uplift and exhumation of source areas and even the subsidence history of sedimentary basins. Although the low-temperature thermochronology of detrital apatite is widely used in sedimentary provenance analysis, the elemental and isotopic geochemistry, as well as the U-Pb dating, remains to be developed. These approaches are supposed to have wide application prospects in several research areas such as tectonics, sedimentary geology basin analysis and even paleoclimatology. 相似文献
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沉积岩中的碎屑组分及主量元素、微量元素和稀土元素可以反映物源信息,广泛应用于沉积源区的确定、构造背景的分析。通过对柴窝铺盆地及北缘地区侏罗纪至古近纪沉积地层的碎屑岩岩石学和地球化学分析,揭示了盆地沉积岩的原岩来自上地壳,岩性以长英质岩石为主,并混合进了部分安山质及基性岩石。源区构造背景为活动大陆边缘,因其原岩是在大陆岛弧环境下形成的,所以部分构造背景显示为大陆岛弧。本次研究不仅可以为柴窝铺盆地及北天山的构造演化过程及其机制提供有力证据,并且对柴窝铺油气勘探具有一定指导意义。 相似文献
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《Chemie der Erde / Geochemistry》2019,79(1):94-112
To constrain the tectonic evolution of the eastern segment of the Paleo-Asian Ocean, we conducted zircon U–Pb-Hf dating and whole-rock geochemical analyses for metasedimentary rocks from the Dongnancha Formation in the Huadian area in central Jilin Province, Northeastern (NE) China. Most detrital zircons from the metasedimentary rocks display clear oscillatory zoning and striped absorption in cathodoluminescence (CL) images and have Th/U ratios of 0.1–1.8, thus indicating a magmatic origin. U–Pb isotopic dating using LA-ICP-MS method for zircon samples from the metasedimentary rocks reveals that the depositional age can be constrained to the period between 250 and 222 Ma. Geochemical data reveal low to intermediate degrees of weathering of the source material and compositionally low to intermediate maturity. Detailed analyses of detrital zircon U–Pb-Hf geochronology and geochemistry show that these metasedimentary rocks are derived from a bidirectional provenance. The predominant derivation is from Permian–Early Triassic felsic-intermediate igneous rocks of central Jilin Province and adjacent regions in the northern margin of the North China Craton, although felsic-intermediate igneous rocks and continental material in the eastern segment of the Central Asian Orogenic Belt from the Cambrian–Carboniferous represent additional sources and minor amounts of Paleoproterozoic–Neoproterozoic material have been input from the North China Craton. A number of geochemical indicators and tectonic discrimination diagrams collectively indicate a continental island arc-active continental margin setting for the deposition of the protoliths of the metasedimentary rocks. The results of geochemical and geochronological analyses of the provenance and tectonic setting of the metasedimentary rocks indicate that the Dongnancha Formation was likely deposited in an intermountain basin in a post-orogenic fast uplift setting, suggesting that the final closure of the eastern segment of the Paleo-Asian Ocean in the Huadian area of central Jinlin Province likely occurred between the Early Triassic and Middle Triassic. 相似文献
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库车坳陷三叠系发育良好,出露齐全,主要由陆相碎屑岩组成。本文运用电子探针微区成分分析方法,对库车坳陷北部三叠系砂岩中石榴石、电气石、铬尖晶石进行了矿物化学成分分析。结果显示,碎屑石榴石主要富含铁铝榴石,其次为镁铝榴石、锰铝榴石,钙铝榴石含量较低,他们主要来自于低级-高级变质岩和花岗岩;电气石主要来自于变质沉积岩和花岗岩;铬尖晶石则主要源自岛弧玄武岩、洋岛玄武岩和与俯冲相关的橄榄岩。综合石榴石与电气石研究结果表明,上三叠统碎屑物质更多的来自于高级变质岩和花岗岩,而下三叠统碎屑物质主要源自低级变质岩和花岗岩。通过对比西天山榴辉岩、片麻岩中石榴石成分,本文所研究的高镁石榴石以低钙铝榴石含量与榴辉岩中石榴石相区别,而与片麻岩中石榴石成分相似。西天山榴辉岩在三叠纪时期可能尚未剥露至地表,但片麻岩已有相当范围的出露。上三叠统的碎屑铬尖晶石可能主要来自于中天山及南天山的岛弧岩浆岩及蛇绿岩,部分源自洋岛玄武岩,为南天山为多岛海造山提供了沉积学证据。 相似文献
16.
Mohammad KHANEHBAD Reza MOUSSAVI-HARAMI Asadollah MAHBOUBI Mehdi NADJAFI Mohammad Hosein MAHMUDY GHARAIE 《《地质学报》英文版》2012,86(5):1200-1210
Geochemical analysis of sandstones from the Sardar Formation (from two stratigraphic successions) in east-central Iran were used for identification of geochemical characterization of sandstones, provenance and tectonic setting. Sandstones in the two lithostratigraphic successions have similar chemical compositions suggesting a common provenance. Bulk-rock geochemistry analysis of Carboniferous sandstones from Sardar Formation indicates that they are mainly quartz dominated and are classified as quartzarenites, sublitharenites and subarkoses, derived from acid igneous to intermediate igneous rocks. Discrimination function analysis indicates that the sandstones of Sardar Formation were derived from quartzose sedimentary provenance in a recycled orogenic setting. Also, major and trace elements in sandstones of Sardar Formation (e.g., K2O/Na2O vs. SiO2) indicate deposition in a stable passive continental margin (PM). Chemical index of alteration (CIA) for these rocks (> 65%) suggests a moderate to relatively high degree of weathering in the source area. 相似文献
17.
Ioannis K. Georgiadis Antonios Koroneos Lamprini Papadopoulou Nikolaos Kantiranis Alexios E. Tamparopoulos Ananias Tsirambides 《Mineralogy and Petrology》2014,108(2):187-206
Garnet single crystals of several millimeters in diameter were collected from the uppermost horizon of a soil profile developing immediately on the gneissic rocks of the Vertiskos Unit of the Serbomacedonian Massif in northern Greece. The garnets were analyzed for major elements by EDS analyzer mounted on a scanning electron microscope, and the obtained data were utilized to determine their source rocks. Bivariate diagrams, spider diagrams as well as statistical analysis were used in order to correlate and compare the garnet composition of the basement rocks of the Vertiskos Unit with the existing reference data. This case study demonstrates the difficulty in assigning a source rock to sediment, using only the chemical compositional of detrital garnet. Direct linking of the detrital garnets and the outcropping rocks is not always possible despite well documented outcrop lithologies. This is largely due to a complex metamorphic evolution that leads to overlapping compositions between garnets originating from different lithologies that have undergone similar metamorphic processes and alteration effects. 相似文献
18.
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
19.
Modal analysis, bulk-rock geochemistry and phase chemistry of sandstones of the Miocene Fat'ha and Injana formations, northern Iraq, show that the clastics were derived from heterogeneous sources that include basic igneous and metamorphic rocks as well as older sedimentary rocks. The sandstones are generally carbonate-rich lithic arenites. Their geochemistry supports the petrographic results and indicates that they are all Fe-rich, lithic or quartz arkosic sandstones. According to geochemical data, garnets are derived from metamorphic sources, hornblende is of igneous origin, and clinopyroxenes, are produced by basic igneous rocks. Epidote is most probably to be a product of disintegration of metamorphic rocks, essentially, metamorphosed igneous rocks. Rutile geochemistry implies low-grade metamorphic and basic to ultrabasic igneous sources. Chemical composition of chromian spinels indicates that they are derived from Alpine-type peridotite. The ophiolitic-radiolarite belts of Taurus-Zagros as well as the uplifted Cretaceous and Paleocene strata of north and northeastern Iraq are likely to be the major source of clastics to the Fat'ha–Injana basin, a foreland basin formed as a result of the continental Arabian and Turkish/Iranian plates collision. 相似文献