Mineralogy,M-type tetrad effect and radioactivity of altered granites at the G. Abu Garadi shear zone,central Eastern Desert,Egypt     

El Nahas H.A.  El Feky M.G.  Mira H. 《中国地球化学学报》2011,30(2):153-164

The G. Abu Garadi area is covered mainly by metasediments, alkali feldspar granites and stream sediments. The alkali feldspar granite is traversed by a major strike-slip fault trending in an N-S direction as well as two subordinate sets of faults trending NW to WNW for the first one and NE for the second one. These faults represent the shear zones affected by magmatic (syngenetic) as well as hydrothermal (epigenetic) activities causing alteration of the granitic rocks. The most common alteration features are albitization, greisenization and koalinitization. The mass balance calculations of the studied altered samples show enrichments in Zr, Y, Ni, U, Th and Ga and depletions in Zn, Sr, Nb, Ba, Pb, Cu and V. Only the greisenized samples exhibit a significant enrichment in Nb, ∑REE budget and pronounced lanthanide tetrad effect (M-type), especially TE1,4, while weakly expressed tetrad effects are for the other albitized and koalinitized samples. Mineralogically, the common accessory minerals in the altered samples include samarskite-(Y), betafite, uranothorite, zircon, fluorite and cassiterite. The greisenized granites contain high eU and eTh than the other altered types, where they are characterized by an assemblage of the radioactive minerals; samarskite-(Y), betafite, uranothorite in addition to zircon. The inter-element relationships between U and Th and also their ratios illustrate that the radioelement distribution in these granites is mainly governed by magmatic processes, in addition to post-magmatic ones. The distribution of chemical elements and the fractionation of some isovalents within the shear zone are largely controlled by the newly formed mineral phases. With respect to uranium mobilization, uranium migrated from the host alkali feldspar granites of G. Abu Garadi, while the shear zones acted as traps for the migrated uranium. Moreover, U migrated in the shear zone during greisenization and albitization, and migrated out during koalinitization.  相似文献   

Petrogenesis of granitic rocks of the Jabal Sabir area,South Taiz City,Yemen Republic     

Rasmy I.El-Gharbawy 《中国地球化学学报》2011,30(2):193-203

The Tertiary granitic intrusive body(～21 Ma) of the Jabal Sabir area was emplaced during the early stages of the Red Sea opening.This intrusive body occupies the southern sector of Taiz City.It is triangular in shape,affected by two major faults,one of which is in parallel to the Gulf of Aden,and the other is in parallel to the eastern margin of the Red Sea coast.The petrogenesis of such a type of intrusion provides additional information on the origin of the Oligo-Miocene magmatic activity in relation to the rifting tectonics and evolution of this part of the Arabian Shield.The granitic body of Jabal Sabir belongs to the alkaline or peralkaline suite of A-type granites.It is enriched in the REE.The tight bundle plot of its REE pattern reflects neither tectonism nor metamorphism.This granite body is characterized by high alkali(8.7%-10.13%),high-field strength elements(HFSE),but low Sr and Ba and high Zn contents.The abundance of xenoliths from the neighboring country rocks and prophyritic texture of the Jabal Sabir granite body indicate shallow depths of intrusion.The major and trace elements data revealed a fractional crystallization origin,probably with small amounts of crustal contamination.It is interpreted that the Jabal Sabir intrusion represents an anorogenic granite pertaining to the A-type,formed in a within-plate environment under an extensional tectonic setting pertaining to rift-related granites.  相似文献   

华南印支期产铀和非产铀花岗岩黑云母矿物化学成分差异   总被引：6，自引：0，他引：6  

章健  陈卫锋  陈培荣 《大地构造与成矿学》2011,35(2):270-277

华南印支期花岗岩与铀成矿关系密切.根据花岗岩赋存铀矿的能力,将华南印支期花岗岩分为产铀花岗岩和非产铀花岗岩.前者以诸广山岩体和大富足岩体为代表,后者以白马山岩体和瓦屋堂岩体为代表.利用黑云母电子探针矿物化学成分来研究产铀与非产铀花岗岩的特征和差异,进一步指导华南印支期花岗岩的铀矿找矿勘探工作.与非产铀花岗岩相比,产铀花...  相似文献   

中国东南部中生代基性岩脉时空分布与形成机理   总被引：2，自引：1，他引：1       下载免费PDF全文

娄峰  马浩明  刘延勇  李宏卫  杨燕娜  陈耀均 《地学前缘》2011,18(1):15-23

中国东南部发育的基性岩脉见于中生代各个时期,其年龄从内陆至沿海逐渐变新,与区内花岗岩年龄有相同的变化趋势,但两者活动高峰期不重合。基性岩脉主要发育于花岗岩体内部的拉裂带,鲜见穿过花岗岩上方或周围的沉积变质盖层。中生代各时期的基性岩脉与相应时期的中酸性和基性火山岩浆活动具有清晰的分带现象。进一步研究表明,基性岩脉与同期基性火山岩应是同源不同相的产物,而中酸性喷发的岩浆与基性喷发(侵入)的岩浆,则可能分别来自壳内熔融层和壳下(地幔)熔融层或壳内岩浆层的上部和下部。中酸性与基性岩浆活动的"错峰"现象和基性岩脉带的"迁移"现象,均与本区中生代陆壳系统的内能变化有关。  相似文献   

华南花岗岩暗色微粒包体的岩石化学组成特征及其意义   总被引：2，自引：0，他引：2       下载免费PDF全文

彭卓伦  Rodney Grapes  庄文明  张献河 《地学前缘》2011,18(1):74-81

对华南诸多花岗岩体暗色微粒包体的野外调查表明, 非均一包体是包体中最普遍的类型,常具有暗色基性边.岩石化学分析结果表明,包体边缘的岩性为二长岩-石英二长岩-二长闪长岩,中心则为石英二长闪长岩-英云闪长岩.从包体中心到边缘,具有Si、Ca含量和Na/K比值降低,K、Al、Ti、P和Fe+Mg含量升高的变化趋势,揭示包体应...  相似文献   

赣南区域铀成矿特征     

钟启龙 《国外铀金地质》2011,(3):147-150,162

归纳总结赣南地区不同类型铀成矿特征,认为赣南铀成矿具有多期、多阶段的特点,提出区域铀成矿控制因素主要为富铀变质岩基底、富铀岩浆岩和断裂构造。  相似文献   

福州花岗岩区大直径地热深井主要钻井技术     

田勇 《福建地质》2011,30(2):177-182

在福州大直径地热深井钻探施工中,使用钻井能力大于600m的大型水文钻机及相关配套设备,选用HA、HJ系列掌背强化金刚石保径、中-高抗压强度镶齿三牙轮钻头,采用 气举反循环钻井工艺,成功施工十余口550～1 200m优质高温大口径地热深井,介绍了其主要钻井技术,对今后深层回灌钻井施工具积极的作用.  相似文献   

福建泉州笔架山花岗瓷石矿地质特征及成因分析     

林耀忠 《福建地质》2011,30(3):218-223

泉州笔架山花岗瓷石矿贮存于钾长花岗岩中心柏和花岗斑岩中,矿石化学成分高硅、富、碱、贫铁镁。矿体埋藏浅、质优、规模大、易采易选易加工。开发利用远景看好。  相似文献   

老挝中北部花岗岩地球化学特征及其地质意义   总被引：2，自引：0，他引：2  

贾润幸  方维萱  胡瑞忠 《矿物岩石》2011,31(3)

老挝NM矿区位于中北部长山(Truong Son)岩浆-构造内。在二叠-三叠纪的印支运动期间,Sibumasu板块沿Nan-Uttaradit缝合线与印支板块拼接后,在印支板块的东部形成了北西向右旋的长山(Truong Son)岩浆-构造剪切带。NM矿区的花岗岩可分为中粗粒花岗岩、斑状花岗岩和细粒花岗岩。本区不同类型花岗岩的地球化学特征显示其ACNK值多介于0.9～1.1之间,为高钾钙碱性花岗岩;微量元素中多富集Cs,Rb,Th,U,K而相对亏损Ba,Sr等大离子亲石元素,高场强元素分异明显,Nb,P,Ti表现出明显的负异常;稀土元素相对富集轻稀土,轻稀土元素分馏程度高而重稀土元素分馏程度不明显,铕具中等或明显的负异常,上述特征表明本区不同类型花岗岩的物质来源相似。结合本区的大地构造特征和花岗岩的地球化学特征来看,本区花岗岩可能形成于印支碰撞造山后期的挤压-剪切环境。同时岩浆在从中粗粒花岗岩向斑状花岗岩和细粒花岗岩的结晶演化过程中,TFe,TiO2,MgO,CaO,Na2O的含量逐渐降低,而SiO2和K2O的含量相对增加,Fe,Cu,Zn(Pb)等矿化主要与其中的斑状花岗岩的关系较为密切。  相似文献   

New U-Pb zircon and Ar/Ar muscovite age constraints on the emplacement of the Lizio syn-tectonic granite (Armorican Massif, France)     

Romain Tartèse  Marc Poujol  Gilles Ruffet  Philippe Boulvais  Philippe Yamato  Jan Košler 《Comptes Rendus Geoscience》2011,343(7):443-453

LA-ICP-MS U-Pb analyses performed on zircon grains from the Lizio granite yielded an emplacement age of 316 ± 6 Ma. Typical S-C structures show that the Lizio granite was emplaced contemporaneously with dextral shearing along the northern branch of the South Armorican Shear Zone and that it was therefore active at that time. ⁴⁰Ar/³⁹Ar analyses performed on muscovite grains yielded plateau dates ranging between 311.5 and 308.2 Ma. Muscovite chemistry is typical of primary magmatic muscovite, which precludes a late fluids-induced resetting of the K-Ar isotopic system. ⁴⁰Ar/³⁹Ar dates thus likely correspond to the cooling ages below the argon closure temperature. Considering the uncertainties on the measured ages, we can propose that either the Lizio granite cooled down quickly in less than a million of years or that it remained in a hot environment for several millions of years after its emplacement. This latter scenario could have been sustained by shear heating during dextral shearing along the northern branch of the South Armorican Shear Zone.  相似文献