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   

福建湄州岛镁铁质岩墙群与寄主花岗岩的形成时差、地球化学及成因   总被引：2，自引：0，他引：2  

董传万  周超  顾虹艳  马骁雄  吕青 《吉林大学学报(地球科学版)》2011,41(3):735-744

福建湄洲岛的镁铁质岩墙群侵入于花岗岩中。镁铁质岩墙主要由斜长石(An=45~55,中-拉长石)、普通角闪石及少量辉石和石英等组成,锆石SHRIMP U-Pb年龄为(95±2)Ma。寄主花岗岩主要由石英、钾长石、斜长石(An=22~25,更长石)及少量的黑云母组成,锆石SHRIMP U-Pb年龄为(105±3)Ma。它们的形成时差约10 Ma。在岩石地球化学上,镁铁质岩墙群具有低CaO、MgO、TiO2而高Al2O3、轻稀土元素和大离子亲石元素富集、高场强元素亏损等特点,(87Sr/86Sr)i=0.705 2~0.705 4,εNd(t)=-0.03~1.57,与福建沿海同时代镁铁质岩墙群相似。寄主花岗岩与沿海高钾钙碱性花岗岩基本相同,都具有高硅、富碱的特点,它们的w(SiO2)>75%,A/CNK=1.05~1.12,w(K2O+Na2O)=7.68%~8.12%,w(K2O)>w(Na2O),(87Sr/86Sr)i=0.705 5,εNd(t)=-3.92。综合研究表明:湄洲岛寄主花岗岩是由受消减作用影响的岩石圈地幔部分熔融而产生的玄武岩浆底侵,并熔融中下地壳所产生的花岗岩浆形成;而镁铁质岩墙是底侵、滞留并经过结晶分异的玄武质岩浆,因地壳再次伸展,而沿花岗岩体中节理侵入形成。湄洲岛花岗岩与镁铁质岩墙群形成于伸展构造环境,对应福建沿海2次地壳伸展事件。湄洲岛花岗岩和镁铁质岩墙群的研究为沿海晚中生代构造-岩浆活动提供了一个新例证,同时为福建沿海晚中生代岩石圈伸展时限提供了制约。  相似文献   

黑河市五道沟地区早二叠世A型花岗岩成因   总被引：1，自引：0，他引：1  

郭奎城  张文龙  杨晓平  王磊  史冬岩  于海涛  苏航 《吉林大学学报(地球科学版)》2011,41(4):1077-1083

根据岩石学、岩石化学、地球化学及同位素等特征,对黑河市五道沟地区早二叠世碱长花岗岩进行了构造成因研究。该套岩石具高硅、富碱、低钙镁、偏铝质-过铝质特点,且富Rb、Th、K等大离子亲石元素,相对亏损Ba、Sr、P、Ti、Nb等元素,稀土元素具有典型的海鸥式分配样式,总体具有典型A型花岗岩特征;其形成于额尔古纳—兴安地块与松嫩—张广才岭地块挤压拼贴后的伸展环境。黑河市五道沟地区A型花岗岩的最新厘定对该地区晚古生代构造演化的研究及区域成矿规律的探讨具有重要意义。  相似文献   

渭河盆地富氦天然气井分布特征与氦气成因     

李玉宏  卢进才  李金超  陈高潮  魏仙样 《吉林大学学报(地球科学版)》2011,(Z1):47-53

渭河盆地的石油钻井、地热井及秦岭北缘水文井中普遍发现含高体积分数氦气显示,其氦体积分数之高为国内外少见。渭河盆地天然气氦同位素3He/4He为(2.1～76.0)×10-8,属壳源氦,个别样品有少量幔源氦加入,形成了独特的壳源高氦-富氦天然气。氦气体积分数较高井临近富铀、钍的花岗岩体,说明壳源氦来源于花岗岩的放射性衰变;个别样品有一定的幔源氦加入,表明区内也有一定的幔源氦运聚过程。渭河盆地新近—古近系具有良好圈闭与运移条件,为氦气赋存提供了良好条件。  相似文献   

桂北摩天岭含铀花岗岩体岩石地球化学特征   总被引：2，自引：0，他引：2  

邹明亮  舒孝敬  范立亭  梁永东 《矿物岩石地球化学通报》2011,30(4):415-422

本文按摩天岭含铀花岗岩体的花岗岩、弱蚀变花岗岩、钾交代花岗岩和硅质交代花岗岩4种岩石类型,探讨了岩石中的常量元素、大离子亲石元素(LILE)、高场强元素(HFSE)和稀土元素(REE)含量特征及相互间的关系。其中含铀钾交代花岗岩表现为强钾长石化、强绿泥石化和弱赤铁矿化,U含量与次生黑云母关系密切;含铀硅质交代花岗岩的U含量与微晶石英伴生的铁质有关。通过剖析不同类型岩石的地球化学特征,指出成矿流体的元素主要来自花岗岩,产铀岩石具明显的LLH特征;伴随铀矿化的增强,K/Ba、Rb/Sr值降低,而Ba/Rb值增高;含铀钾交代花岗岩和硅质交代花岗岩的HFSE和REE含量呈共轭消长和重稀土(HREE)相对富集的特征。提出伴随断裂开启多期成矿流体的叠加更有利于铀的富集,LLH特征,以及K/Ba、Rb/Sr值降低与Ba/Rb值增高可作为含铀花岗岩体的地球化学判别依据。  相似文献   

皖南及邻区燕山期两个类型花岗岩地球化学对比与岩石成因   总被引：9，自引：0，他引：9  

翁望飞  支利庚  蔡连友  徐生发  王邦民 《矿物岩石地球化学通报》2011,30(4):433-448

皖南周边分布着40余处大小不等的燕山期花岗岩体,依据岩石年龄可划分出2个幕次:一是130～170Ma,平均145Ma,为晚侏罗世-早白垩世早期(J3-K11),以花岗闪长(斑)岩为主;二是109～132.2Ma,平均123.5Ma,为早白垩世中、晚期(K12),岩性为花岗岩。研究表明,J3-K11花岗闪长岩为C型、高钾钙碱性埃达克岩,发育于造山后构造,应力由挤压转变为伸展的转折期,源自印支期加厚地壳部分熔融。而K21幕花岗岩为A2型花岗岩,产生于造山后的构造伸展环境,源自正常安山质地壳在印支期加厚地壳熔融结束之后继续受地幔物质底侵部分熔融。埃达克岩与斑岩铜矿及金、银等矿床成因上密切相关,A型花岗岩富集稀土元素及W、Zr、Nb、Ta、U等。因此加强皖南及邻区埃达克岩和A型花岗岩的研究,可为该地区寻找斑岩铜矿床及稀土、稀有金属等矿床提供一个新的思路和方向。  相似文献   

Application of a coil‐type TDR probe for measuring the volumetric water content in weathered granitic bedrock     

Shin'ya Katsura  Ken'ichirou Kosugi  Takahisa Mizuyama 《水文研究》2008,22(6):750-763

As a first step toward describing water flow processes in bedrock, a coil‐type time domain reflectometry (TDR) probe capable of measuring volumetric water content, θ, in weathered bedrock at three depths was prepared. Because the coil‐type TDR probe is large in diameter (19 mm), it can be installed even in highly weathered bedrock more easily and appropriately than conventional TDR probes that consists of two or three rods of small diameter (5‐8 mm). The probe calibrations suggest that the values measured by the probe are very sensitive to changes in θ. Using the calibrated probe together with commercially available profile soil moisture sensors, the θ profile was monitored for 1 year. Even rainfall events with relatively small cumulative rainfall of 15 mm increased the bedrock θ, and the increments were comparable to those in the soil. After the end of the rainfall events, the bedrock θ displayed a more rapid drop than the soil, and varied little during the period of no rainfall. The water storage showed similar tendencies. These observations suggest that the bedrock θ is controlled by clearly distinguishable macropores and micropores within the bedrock. It is concluded that the coil‐type TDR probe is very effective in determining θ in weathered bedrock, and that bedrock, conventionally defined by conducting cone penetration tests and treated as impermeable, does conduct and hold substantial amounts of water, and therefore contribute greatly to hydrological processes in headwater catchments. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

登封箕山北麓硅化破碎带含矿地质特征     

赵华中  李国忠  左培锦 《河南国土资源》1994,(2)

登封箕山北麓硅化破碎带主要产于上寒武统白云岩中，成群成带分布。矿化严格受地层、岩性、构造条件控制。本文着重硅化破碎带的含矿地质特征、矿化类型、元素组合、异常分布和围岩蚀变等成矿地质条件分析研究，认为太古代变质绿岩和富钾花岗岩类是“矿源层”，其成因应属低温热液充填型。  相似文献   

Analytical simulation of the dynamic compressive strength of a granite using the sliding crack model     

H. B. Li  J. Zhao  T. J. Li  J. X. Yuan 《国际地质力学数值与分析法杂志》2001,25(9):853-869

A sliding crack model is employed to simulate rock strength under dynamic compression. It is assumed that the growth and nucleation of a sliding crack array presented results in the shear fault failure and dominate the mechanical properties of rock material. The pseudo‐tractions method is used to calculate the stress intensity factor of the sliding crack array under compression. With the utilization of a dynamic crack growth criterion, the growth of the sliding crack array is studied and the simulated strengths of a granite under dynamic compression are correspondingly obtained. It is concluded that the simulated rock strengths increase with increasing strain rates at different confining pressures, and the rising rates have a trend to decrease with increasing confining pressures. It is also indicated that the simulated rock strengths increase with increment of confining pressure at different strain rates, and the rising rates are almost identical at different strain rates. The simulation results are validated by the experimental data for the granite. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献