Structure, geometry and formation of brittle discontinuities in anisotropic crystalline rocks of the Central Gotthard Massif, Switzerland     

Christian Zangerl  Simon Loew  Erik Eberhardt 《Eclogae Geologicae Helvetiae》2006,99(2):271-290

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Fluid Transfer in High-grade Metamorphic Terrains Intruded by Anorogenic Granites: The Thor Range, Antarctica     

BUCHER  KURT; FROST  B. RONALD 《Journal of Petrology》2006,47(3):567-593

A composite intrusive igneous complex in the central mountainrange of Queen Maud Land (Thor Range), Antarctica, displayscharacteristic features of anorogenic granites. A suite of massiveintrusives and various sets of dykes and satellite intrusionsare ferroan, alkalic to alkali–calcic, and weakly peraluminous.An early set of plutons consists of charnockitic alkali-granites;a later group of plutons comprises fayalite Qtz-syenites. Coarsemesoperthite is the dominant mineral in all rocks, quartz isabundant and plagioclase is a minor mineral. Olivine (fayalite)is the characteristic mafic mineral, but subcalcic augite andoccasionally pigeonite or orthopyroxene are present. In mostsamples, amphibole is the dominant mafic mineral and its compositionis close to end-member hastingsite. It contains high concentrationsof F and Cl. Some samples contain igneous fluorite. Thermobarometrysuggests a temperature of 900 ± 25°C and a pressureof 0·4 ± 0·1 GPa for the crystallizationconditions of the pyroxene–olivine assemblages. The solidustemperature of 800–850°C for both suites of plutonicrocks is typical of water-deficient granitic melts. The estimatedlow water activity of 0·3–0·5 at solidusconditions is consistent with the high halogen content of thebulk-rocks and their constituent minerals. In the absence ofan aqueous fluid, the halogens remained in the minerals at thesolidus. Oxygen fugacity stayed below QFM in all igneous rocksabove solidus. This is typical of melts derived from partialmelting of mafic source rocks. The igneous rocks were locallyaffected by at least three distinct episodes of hydration. Asthe melt approached solidus conditions, fayalite and pyroxenewere locally transformed into hastingsite as a result of increasingfugacity of volatile components. Fayalite-free and fayalite-bearingigneous rocks are arranged in banded structures. Subsolidushydration locally modified the igneous rocks and transformedpyroxene- and fayalite-bearing granites into biotite-granitesand hornblende-granites in which all evidence of former high-Thistory was erased. This local hydration of igneous rocks occurredin response to uptake of H₂O that had been given off by gneissicxenoliths as a result of progressing, continuous, dehydrationreactions. The reactions in the gneiss xenoliths were drivenby contact metamorphism. This exchange of H₂O between igneousand metamorphic rocks occurred in a fluid-absent regime at temperaturesof about 750°C. Late reaction veins formed by hydraulicfracturing of the plutonic rocks and indicate the presence ofa low-density fluid phase at amphibolite facies conditions. KEY WORDS: anorogenic granite; fayalite; hastingsite; fluid recycling; Antarctica  相似文献   

西藏西北部旋风沟地区古近纪潜花岗斑岩的发现及意义     

钟华明  童劲松  夏军  鲁如魁 《安徽地质》2006,16(4):247-251,261

潜花岗班岩为火山颈相,其锆石U-Pb同位素年龄为32±0.2Ma。岩石具有富Al、Th和LREE特征,Eu负异常不明显,表明不是由基性浆演化而成,而是由加厚陆壳底部熔融形成的。结合区域构造、沉积记录和火山岩组合特征,潜花岗斑岩形成于大陆拉张环境。潜花岗斑岩年龄的确定制约了新生代沉积地层的年代,同时也为藏北地区陆内拉张时代的确定提供了依据。  相似文献   

LA-ICPMS Zircon U-Pb Dating for Three Indosinian Granitic Plutons from Central Hunan and Western Guangdong Provinces and Its Petrogenetic Implications   总被引：1，自引：0，他引：1  

PENG Bingxi  WANG Yuejun  FAN Weiming  PENG Touping  and LIANG Xinquan Key Laboratory of Isotope Geochronology  Geochemistry  Guangzhou Institute of Geochemistry  Chinese Academy of Sciences  Guangzhou  Guangdong Graduate School of the C 《《地质学报》英文版》2006,80(5):660-669

1 Introduction Much attention has been paid to the structure, magmatism and sedimentation associated with the Indosinian Orogeny within the South China Block (SCB) since Deprat (1914) and Fromagat (1932) proposed the term “Indosinian movement” based on two unconformities between pre-Norian and pre-Rhaetian times during the early Triassic in Vietnam. However, this timing has been debated in terms of the Indosinian tectonic evolution within the SCB (Guo et al., 1983; Hsü et al., 1990…  相似文献   

福建石牛山水蚀花岗岩石蛋地貌特征及成因研究   总被引：2，自引：0，他引：2  

梁诗经  文斐成  陈斯盾  揭育金  魏勇  胡祚林 《福建地质》2006,25(2):65-74

石牛山主峰出露晚白垩世石牛山组晚期侵入相钾长花岗斑岩,山体浑厚壮观,石蛋千姿百态。石蛋、石堡及崖壁上分布着深浅不一的石脊、石槽及大小不同的石臼、石盆、石穴等微地貌,构成独具特色的“水蚀花岗岩石蛋地貌”。经研究,钾长花岗斑岩是形成水蚀花岗岩石蛋的物质基础,风化剥蚀、大气降水击蚀及其流水侵蚀是形成石脊、石槽、石臼、石盆、石穴的主要外动力地质作用。  相似文献   

华南新元古代裂谷系沉积超覆作用及其开启年龄新证据   总被引：7，自引：1，他引：7       下载免费PDF全文

王剑  曾昭光  陈文西  汪正江  熊国庆  王雪华 《沉积与特提斯地质》2006,26(4):1-7

黔东南1∶5万高武幅、宰便幅区域地质调查结果表明,新元古界下江群是一套沉积超覆于中元古界四堡群之上的裂谷系楔状地层,其底部甲路组沉积底砾岩高角度(不整合)沉积超覆于四堡群复理石浊积岩之上,或沉积超覆于侵入四堡群之中的摩天岭花岗岩之上。取自该地区沉积超覆面之下摩天岭花岗岩样品的TIMS锆石U-Pb同位素年龄为825.0±2.4Ma,表明该地区新元古代裂谷系开始接受沉积的时间应该晚于825±2.4Ma;而取自沉积超覆面之上甲路组底部同沉积基性火山岩样品的TIMS锆石U-Pb同位素年龄为814±13Ma,这一年龄大致代表了该地区新元古代沉积超覆的开启时间,且与目前已获得的华南其它地区新元古代裂谷系沉积超覆的开启时间(820Ma)十分接近。本项研究成果支持华南裂谷系沉积超覆的开启时间为820Ma左右的观点。  相似文献   

东天山阿其克库都克断裂南侧花岗岩和花岗闪长岩锆石SHRIMP U-Pb测年及其地质意义   总被引：11，自引：2，他引：11  

孙桂华  李锦轶  王德贵  高立明  宋安江 《地质通报》2006,25(8):945-952

东天山地区古生代的构造格局一直是地质界争议的问题之一.本文对阿其克库都克断裂南侧花岗岩和花岗闪长岩2个岩体进行锆石SHRIMP U-Pb定年,分别获得318Ma±5Ma和350Ma±7Ma的206Pb/238U表面年龄,综合分析岩体结构及锆石的矿物学特征,将上述2个年龄分别解释为所研究的花岗岩和花岗闪长岩的侵位年龄.通过对已有资料的综合研究,得出如下结论:①中天山地区在古生代期间的构造背景为类似安第斯型的活动陆缘或岛弧链,其形成与南天山洋盆岩石圈板块向北的俯冲作用有关;②花岗闪长岩锆石中还保留有继承锆石的信息,表明研究区存在老于503Ma±9 Ma的基底物质;③研究区内沿阿其克库都克断裂右行走滑变形事件的下限时间是350Ma±7Ma,很可能发生在石炭纪以后.  相似文献   

豫西南内乡地区金矿成矿与花岗岩、构造的关系   总被引：2，自引：0，他引：2  

常秋玲  卢欣祥宋锋 《地质通报》2006,25(8):997-1004

对产在河南省内乡地区五朵山花岗岩体内外接触带的金矿床(点)的地质构造背景、矿床地质特征、控矿构造及成矿流体等进行了较为全面的阐述,认为花岗岩与金矿的关系不是直接的而是间接的,构造对金矿的控制是第一位的,区内所有的矿化都受断裂构造的控制.五朵山岩体周围,尤其是西南部的岩体内外接触带、断裂构造发育区、富含黄铁矿和金属硫化物的地段为金矿的有利找矿区.  相似文献   

甘肃北山旧井岩体BS03号钻孔岩石地球化学特征     

范洪海  闵茂中  王驹  陈璋如  金远新  季瑞利  徐健 《铀矿地质》2006,22(2):90-98

文章对旧井岩体BS03号钻孔的岩石学、岩石化学以及同位素地球化学特征等进行了研究。结果表明:BS03号钻孔所见的主要岩石类型为似斑状二长花岗岩,其次为英云闪长岩、石英闪长岩及中粗粒花岗岩、伟晶岩、细晶岩等。似斑状二长花岗岩、黑云母花岗岩以及英云闪长岩的铝碱指数(ASI)为1.0左右,均为准铝质;而石英闪长岩的铝碱指数(ASI)仅为0.66~0.68,表现为明显的铝不饱和。上述各类岩石均表现为I型花岗岩的稀土配分曲线特征,且其稀土配分曲线总体较为相似,说明它们之间具有一定的成因联系。Nd、Sr同位素地质特征揭示:该区花岗岩的成岩物质来源于下地壳,并可能有上地幔物质的介入。  相似文献   

甘肃北山大石山A型花岗岩体的地球化学特征及构造意义   总被引：10，自引：0，他引：10  

齐瑞荣  黄增保  金霞 《岩石矿物学杂志》2006,25(2):90-96

甘肃北山大石山岩体主要由角闪花岗岩和二长花岗岩组成,岩石的化学成分特点为过铝质(Al_2O_3含量为 12.18%～13.37%)、富硅(SiO_2含量为74.22%～78.38%)、偏碱(Na_2O+K_2O 为7.60%～8.50%),FeO~T/MgO 值高,CaO 和 MgO 含量低(分别为0.01%～0.99%和0.05%～1.15%),富含 Y、Nb 等高场强元素(HFSE)以及 F、Sr、 Ba 和 REE(∑REE=102.3×10~(-6)～120.02×10~(-6))低。这些特点与本区的 I 型和 S 型花岗岩有明显差别,是一种典型的 A_2型花岗岩。大石山岩体 Rb-Sr 等时线年龄为273 Ma,表明北山地区在海西晚期即进入造山后拉张裂解环境。  相似文献