黑龙江金厂铜金矿区晚三叠世—早侏罗世花岗杂岩锆石U—Pb定年和岩浆热演化史示踪

黑龙江金厂铜金矿床地处兴蒙造山带的北东端,兴凯—延边中生代岩浆构造带北部。对该矿区花岗岩杂岩体开展锆石CL图像、U--Pb定年和演化史示踪,结果表明它较好地记录了该区晚三叠世早期—早侏罗世岩浆连续作用的热演化史。岩浆演化大致经历了6个阶段:岩浆房冷却结晶、早期岩浆缓慢结晶、岩浆上涌过程中快速结晶、主体花岗岩浆降温结晶、晚期岩浆热液结晶和残余岩浆热液结晶过程。整个岩浆演化过程至少经历了23Ma,呈现相对连续的岩浆就位过程。     

江西宜丰县大港超大型含锂瓷石矿床地质特征及成因机制探讨

大港含锂瓷石矿床产于宜丰钽铌锂稀有金属成矿带甘坊花岗岩岩体内,属典型的含锂云母碱长花岗岩型矿床。含锂瓷石矿体厚度21.62～148.88 m,其中w(Al2O3)为15.38%～23.97%,w(Li2O)为0.30%～1.06%,同时伴生Rb、Cs、Ta、Nb等稀有金属。矿石矿物组成为钠长石、锂云母或锂白云母,白度达80%以上。化学组成上,表现出富硅,贫铁、镁、钛,高磷的特征;铝饱和指数A/CNK值大于1.20,Zr/Hf比值(<12)与Nb/Ta比值(<2)极低,表明具有高分异的过铝质S型花岗岩特性。由构造环境判别图解可知,大港含锂云母碱长花岗岩应形成于同碰撞或后碰撞早期阶段的伸展构造背景下,极低的CaO/Na2O比值(<0.2),指示岩体的源区应为富黏土矿物的变质泥质岩。     

辽北西丰地区晚侏罗世营厂岩体LA-ICP-MS锆石U-Pb年龄及岩石地球化学特征

营厂岩体分布于辽北西丰县和隆镇境内，研究结果表明，该岩体主要为似斑状二长花岗岩，锆石²⁰⁶Pb/²³⁸U年龄加权平均值为156.1 Ma±1.5 Ma，形成时代为晚侏罗世。营厂岩体w（Na₂O）/w（K₂O）平均值为1.07，属高钾钙碱性系列；里特曼指数σ平均值为2.15，属钙碱系列；铝饱和指数A/CNK平均值为1.16，A/CN平均值为1.99，属过铝型；Rb、Sr、Ba、Th、Hf含量偏高，Cr、Ni、Co、V、Rb、Zr、Nb等元素含量低，为"S"型花岗岩特征。稀土元素总量平均值为w（ΣREE）＝82.80×10^-6，w（LREE）/w（HREE）=15.76，w（La）_N/w（Yb）_N=24.32，表明其轻稀土相对富集，重稀土相对亏损，稀土配分曲线右倾。δEu=0.80，铕弱负异常，说明成因与板块运动有关，w（Sm）/w（Nd）=0.20，w（Ba）/w（Sr）=1.60，w（K）/w（Rb）=249.15，表明具有壳源性质。营厂岩体具有埃达克岩的特点，其属于受太平洋板块向欧亚板块俯冲作用的影响，在挤压环境下加厚下地壳部分熔融，从而形成活动陆缘型花岗岩。     

Geochronology,petrogenesis and tectonic implications of the Zhongchuan granitic pluton in the Western Qinling metallogenic belt,China

The Zhongchuan district is an important component of the metallogenic belt in the Western Qinling. The Zhongchuan granite pluton occurring in the centre of the Zhongchuan metallogenic area has been poorly constrained, though the Triassic granite in Western Qinling has been well documented. In‐situ zircon U–Pb ages, Hf isotopic compositions and whole‐rock geochemical data are presented for host granite and mafic microgranular enclaves (MMES) from the Zhongchuan pluton, in order to constrain its sources, petrogenesis and tectonic setting of the pluton. The distribution of major, trace and rare earth elements apparently reflect exchange between the MMES and the host granitic rocks mainly due to interactions between coeval felsic host magma and mafic magma. The zircon U–Pb age of host granite (231.6 ± 1.5 to 235.8 ± 2.3 Ma) has overlapping uncertainty with that of the MMES (236.6 ± 1.3 Ma), establishing that the mafic and felsic magmas were coeval. The Hf isotopic composition of the MMES (ε_Hf(t) = −13.4 to 4.0) is distinct from the host granite (ε_Hf(t) = −15.7 to 0.0), indicating that both enriched subcontinental lithosphere mantle (SCLM) and crustal sources contributed to their origin. The zircons have two‐stage Hf model ages of 1064 to 1798 Ma for the host granite and 858 to 1747 Ma for the MMES. This suggests that the granitic pluton was likely derived from partial melting of a Late Mesoproterozoic crust, with subsequent interaction with the SCLM‐derived mafic magmas in tectonic affinity to the South China Block. Copyright © 2012 John Wiley & Sons, Ltd.     

广西花山航空伽马能谱特征及找矿预测

广西花山岩体为多期（次）侵位花岗岩体，在岩体内部具有良好的铀成矿地质条件。文章基于航空伽马能谱实测资料，对花山花岗岩体的放射性分布特征进行了研究。研究结果显示，花山岩体整体处于放射性偏高场-高场区域，岩体中心偏南部位的铀含量有明显增高趋势，望高单元的核部和华美单元具有明显的铀迁入特征，F参数高值区分布在望高单元的核部，根据元素的迁移富集规律，圈定出铀矿成矿的有利部位，为扩大华南地区铀矿勘探区域提供了地球物理基础资料。     

东喜马拉雅构造结南迦巴瓦岩群花岗质片麻岩的初步研究

野外地质填图和研究发现,东喜马拉雅构造结高喜马拉雅结晶岩系中有古老的花岗岩侵入,并在鲁霞地区圈定了9个花岗质侵入体。古老的花岗质岩石主要侵位于南迦巴瓦岩群直白岩组中,与南迦巴瓦岩群一起经历了麻粒岩相变质作用而形成花岗质片麻岩套。岩石类型有花岗闪长质片麻岩、黑云母花岗质片麻岩、闪长质片麻岩等。岩石化学研究表明这些花岗片麻岩套具“S”型特征,可能有深部幔源物质的加入。花岗岩形成深度在2～5km之间．侵位时代为552～525Ma,为新元古代晚期,属泛非期陆内演化阶段的产物。高喜马拉雅地区在元古宙末期形成了结晶基底。     

糜棱岩化过程中锆石的稳定性 ——以西南三江高黎贡、西盟地区花岗质糜棱岩为例

自然条件下锆石的稳定性对于合理解释锆石年龄及深入理解锆石同位素年代学有重要意义.本文对西南三江造山带高黎贡山和西盟地区的花岗质糜棱岩进行了显微构造和锆石U-Pb年代学研究.高黎贡山和西盟糜棱岩中主要造岩矿物长石、石英、云母发生了明显的变形和重结晶,而锆石则以独立晶体或以残留核的形式保存了原始的岩浆结构.高黎贡山和西盟糜...     

陕西丹凤富铷伟晶岩中褐钇铌矿矿物学及地球化学特征

东秦岭的商南—丹凤地区分布着众多含稀有金属矿化的花岗伟晶岩,在该地区的富铷花岗伟晶岩中首次鉴定出褐钇铌矿,其主要产出于富石榴子石的微斜长石花岗伟晶岩中,多与石榴子石、锆石、磷钇矿、铌钽铁矿等副矿物伴生,为花岗质岩浆晚期结晶产物.电子探针分析表明,褐钇铌矿除了含有Y、Nb、REE、Ta、Ti等主要元素,还含有较高含量的放...     

U and Th Contents and Th/U Ratios of Zircon in Felsic and Mafic Magmatic Rocks: Improved Zircon-Melt Distribution Coefficients

High-precision data on U and Th contents and Th/U ratios of zircon obtained using secondary ion mass spectrometry analysis have been collected from the literature. Zircon in the granitic rocks has median values of 350 ppm U, 140 ppm Th, and Th/U=0.52; the recommended zircon-melt partition coefficients are 81 for DU and 8.2 for DTh. In zircon from mafic and intermediate rocks, the median values are 270 ppm U, 170 ppm Th, and Th/U=0.81, and the recommended zircon-melt partition coefficients are 169 for DU and 59 for DTh. The U and Th contents and Th/U ratios of magmatic zircon are low when zircon crystallizes in equilibrium with the melt. Increasing magma temperature should promote higher Th contents relative to U contents, resulting in higher Th/U ratios for zircon in mafic to intermediate rocks than in granitic rocks. However, when zircon crystallizes in disequilibrium with the melt, U and Th are more easily able to enter the zircon lattice, and their contents and Th/U ratios depend mainly on the degree of disequilibrium. The behavior of U and Th in magmatic zircon can be used as a geochemical indicator to determine the origins and crystallization environments of magmatic zircon.