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峨眉大火成岩省的岩石地球化学特征及时限 总被引：47，自引：5，他引：47
本文根据盐源－丽江岩区和攀西岩区峨眉山玄武岩的地球化学组成，包括各种氧化物之间的关系、微量元素标准化曲线、Th/Yb与Ta/Yb、Ce/Nb与Th/Nb，以及^87Sr/^86Sr与^143Nd/^144Nd值的相互关系，重点对峨眉山玄武岩地幔源的地球化学特点、上扬子地区岩石圈地幔的地球化学特征及成因、地幔热柱与岩石圈地幔的相互作用，以及峨眉山玄武岩的喷发时限进行了初步探讨。 相似文献
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在北祁连山东段老虎山地区分布着一套奥陶记蛇绿岩，主要包括变质橄榄岩、辉长岩，以及玄武岩和沉积岩互层。沉积岩主要是浊积岩，包括砂岩、粉砂岩，硅岩等。主要元素地球化学特征表明，偏碱性拉斑玄武岩与洋底玄武岩相似。除了个别玄武岩接近N－MORB特征，大多数样品为E－MORB。多数具Nb负异常。地球化学特征表明，老虎山玄武岩形成于弧后盆地。其εNd(t)值在＋3．0－＋8．9之间，（^87Sr/^86Sr)i值为0．7030－0．7060，表明亏损地幔源区中可能有富集地幔成分加入。砂岩岩石学特征和硅岩地球化学特征都表明沉积岩形成于靠近陆缘环境。 相似文献
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峨眉山二滩玄武岩地球化学特征 总被引：3，自引：0，他引：3
峨眉山大火成岩省二滩地区玄武岩w(S iO2)/%=40.5~59.65;普遍高碱,w(K2O N a2O)=2.64%~7.67%。w(T iO2)=2.10%~6.53%,T i/Y>500,该区玄武岩属于高钛(HT)型玄武岩;其M g#=58~84,明显高于高于宾川高钛玄武岩(31~53),说明岩浆演化程度明显低于宾川高钛玄武岩浆。岩石样品中Sr显示明显负异常,暗示了二滩玄武岩经历了广泛的斜长石结晶分离;而Eu不显异常,则反映了玄武岩岩浆中有高Eu3 /Eu2 比值的存在,其环境为氧化环境。在二滩玄武岩和宾川高钛玄武岩中,N i,Z r,T iO2和M g#均显示了明显差异,说明二滩玄武岩具有独立的地球化学特征。二滩玄武岩不相容元素(R b,B a,Th,U,N b,T a,L a,C e等)配分曲线与O IB相似,及其T a/Y b vs Th/Y b双变量图解也显示出了富集地幔特征,这些特征反映了峨眉山二滩玄武岩源区为富集地幔源,玄武岩岩浆可能为地幔柱物质。此外,B a/Th,Z r/N b,L a/N b,B a/N b等比值介于EM I O IB和EM II O IB之间,以及C e/Pb比值也说明:二滩玄武岩缺少H IMU O IB端元组分,是EM I O IB和EM II O IB两端元的混合产物。 相似文献
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分布于云南宾川地区、厚逾5000m的晚二叠世峨眉山玄武岩以拉斑玄武岩为主,少量碱性玄武岩。根据它们的岩相学和主量元素、微量元素特征,将其划分为两个地球化学类型:低钛玄武岩(LT)和高钛玄武岩(HT)。低钛玄武岩主要分布于岩石剖面的中下部,其主要地球化学标志为低Ti/Y(<500),高Mg#(048～067),低的∑REE(<120μg/g)、(La/Yb)N(<6)和(Sm/Yb)N(<25)。高钛玄武岩分布于剖面的顶部,以高Ti/Y(>500),低Mg#(039～053)、高的∑REE(>150)、(La/Yb)N(>9)和(Sm/Yb)N(>3)为特征。根据LT的分异指数和Th、U异常特征等,将其分为LT1和LT2两个亚类。其中LT1位于岩石剖面下部,表现为明显的Th和U正异常,高Mg#(061～067)和低Nb/U比值等。LT2位于岩石剖面中部,具Rb、Ba正异常,无Th和U异常和较低的分异指数(Mg#=048～054)。LT玄武岩可能是峨眉地幔热柱主活动期地幔柱头部熔融的产物,后经较弱的橄榄石+单斜辉石±斜长石结晶分异形成。剖面最底部的LT1玄武岩显示较强的“壳源”印记,可能与岩石圈地幔中富集组份的活化有关。这些壳源物质的参与程度自底部向上有降低的趋势。晚期HT玄武岩为地幔热柱消亡期的产物,其在地壳浅部经历强烈的以斜长石为主的结晶分异,壳源物质的混染不明显。 相似文献
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研究区峨眉山玄武岩分布于扬子地块西缘,冈达概组分布于其邻区的中咱微陆块。峨眉山玄武岩与冈达概组下段玄武岩均具有富碱、高钛特征,大部分属于碱性玄武岩系列,峨眉山玄武岩Mg#变化范围为0.31~0.70,属于适度演化过的岩浆,冈达概组下段玄武岩Mg#=0.34~0.43。总体上,冈达概组下段玄武岩比峨眉山玄武岩更富Ti,高FeO*,低MgO,低SiO2。两组玄武岩均有轻稀土强烈富集的特征,富集大离子亲石元素和高场强元素,但部分具有Sr、Zr负异常,均属板内玄武岩,岩浆来源于富集地幔,在地幔柱作用下产生。峨眉山玄武岩Rb、Ba有明显的波动,可能是受到源区混染作用影响,其微量元素比值表现出EM1-OIB与EM2-OIB的混合特征,起源于石榴石二辉橄榄岩,熔融程度为4%~7%。冈达概组下段玄武岩元素比值较稳定,与EM1-OIB具有很大的相似性,也起源于石榴石稳定区,其形成深度比峨眉山玄武岩深,熔融程度较低,为2%~5%,可能是产生于地幔柱边缘。中咱微陆块、扬子地台西缘的二叠系玄武岩源区物质均受峨眉山地幔柱影响,具有很大的亲源性,峨眉山地幔柱的活动为板块的裂解提供了动力。 相似文献
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通过1∶5万区域地质调查,在峨山县甸中地区新发现了镁铁—超镁铁质碱性岩体,其岩性为含石榴磷灰辉石岩及正长辉长岩。岩石地球化学表明,该岩体SiO2含量为（42. 74% ~ 45. 11%）,普遍具有高MgO（8. 78% ~ 11. 13%）、富铁（全铁含量）、低TiO2（0. 88% ~ 2. 45%）,低Na2O（0. 17% ~ 0. 62%）、富碱的特征;富集Rb、Ba、Sr、Th等大离子亲石元素（LILE）,相对亏损Nb、Zr、Ti、Hf等高场强元素（HFSE）及重稀土元素Yb、Y;岩浆形成过程中具中等的部分熔融程度（约10% ~ 15%）,且后期经历了明显的结晶分异作用。对辉石岩及辉长岩进行锆石U- Pb LA- ICP- MS定年,年龄分别为260. 2 ± 1. 6 Ma（MSWD = 0. 4,n= 10）和264. 0 ± 1. 3 Ma（MSWD = 2. 4,n = 23）,属中二叠世晚期,与峨眉山玄武岩具有相似的地球化学特征及侵位年龄。结合区域资料及上述特征,本文认为,峨山县甸中地区镁铁—超镁铁质碱性岩体应属于峨眉山地幔柱活动产物,是峨眉山玄武岩的侵入相,代表了峨眉山玄武岩的一个分枝柱头;本次的发现,对丰富峨眉山大火成岩省资料具有重要的意义。 相似文献
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内蒙古集宁新生代玄武岩的地幔源区特征：元素及Sr-Nd-Pb同位素地球化学证据 总被引：7，自引：8，他引：7
内蒙古集宁玄武岩区位于华北克拉通北缘，东邻汉诺坝玄武岩区。由亚碱性的拉斑玄武岩及碱性的橄榄玄武岩、碧玄岩和碱玄岩组成。玄武岩的SiO2与TiO2含量分别为44．10～52．27wt．％和1．57～2．95wt．％，Mg^#（43—63）及Ni含量（27～210ppm）变化范围较大。集宁玄武岩的微量元素原始地幔标准化曲线及REE球粒陨石标准化曲线与OIB相似，Sr、Nd同位素比值显示了较汉诺坝玄武岩富集的特征。研究表明，虽然集宁玄武岩浆经历了一定程度的橄榄石、单斜辉石的分离结晶作用，但微量元素及Sr、Nd、Ph同位素特征排除了幔源岩浆在喷发到地表过程中受到地壳物质显著混染的可能性。^143Nd／^144 Nd ^87Sr／^86Sr vs．^206Ph／^204Pb的线性相关性表明，集宁玄武岩至少来自两个地幔端元组分：EMI和PREMA，且端元组分与汉诺坝玄武岩相似。尖晶石二辉橄榄岩的低程度部分熔融（2～5％）熔体与石榴石二辉橄榄岩更低程度部分熔融（〈2％）熔体的混合，可以解释集宁玄武岩稀土元素的变化特征。推测EMI位于岩石圈地幔之内且源区深度〈70km，PREMA则来自软流圈地幔。集宁碱性玄武岩与亚碱性玄武岩之间的地球化学差异，可能只是来自岩石圈地幔的EMI型熔体和来自软流圈地幔的PREMA型熔体在形成玄武岩浆时参与混合的比例不同，暗示该地区的岩石圈地幔与软流圈地幔之间经历了强烈的相互作用。集宁玄武岩与汉诺坝玄武岩相似的Sr、Nd、Pb同位素比值及相关性，说明它们具有相似的地幔源区，汉诺坝玄武岩的地球化学差异同样可以用EMI与PREMA组分对岩浆贡献程度的不同来解释。 相似文献
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Emily Keeble David I. Whiteside Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):99-119
Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco. 相似文献
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The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts 总被引：4，自引：0，他引：4
The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H2O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H2O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species. 相似文献
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Muriel Rocher Stéphane Baize Stéphane Jaillet Edward Marc Cushing Yannick Lozac&#x;h Francis Lemeille 《Comptes Rendus Geoscience》2003,335(8):701-708
Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ1 roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003). 相似文献
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正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level 相似文献
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正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7), 相似文献
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正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci- 相似文献
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正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli- 相似文献
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正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.) 相似文献
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正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861 相似文献