桂北豆乍山岩体放射性地球化学特征及其干热岩资源潜力研究

对桂北豆乍山岩体钻孔样品进行了放射性生热元素含量、岩石密度和岩石热导率测试.结果 显示该岩体花岗岩U平均含量为17.49×10-6,Th平均含量为27.54×10-6,K2O平均含量为4.64％,放射性生热率平均值6.46 μW/m3,高于地壳平均值及大部分华南其他岩体的放射性生热率值;岩石密度平均在2.57 g/cm...     

浙江洪公铝质A型花岗岩类的岩石地球化学及其构造环境

初步研究表明,以往被认为是典型的I型花岗岩质岩石的浙江洪公岩体应为铝质A型花岗岩质岩石。该岩体以高钾为特征,K2O 达5％以上,K2O/ Na2O＞1.2,准铝-过铝质（A/NKC=0.80 ～1.14）;FeO*/MgO比值大（平均14.20）,高于M型、S型和I型花岗岩;富含稀土元素（ΣREE=313.09×10-6～523.73×10-6）,具有较高的Ga/Al（′104）值（2.92～4.29）和（Zr+Nb+Ce+Y）元素组合值（551.5′10－6～987.4′10－6）,而亏损Ba、Sr、P、Ti等;Nd同位素模式年龄为1.3—1.6Ga,反映洪公岩体主要起源于地壳物质的部分熔融。区域背景、构造被动定位特点和地球化学综合分析表明,洪公岩体形成于拉张的构造环境。     

粤北地区产铀岩体的铀矿化特征及其成矿机制探讨

粤北地区是中国花岗岩型铀矿最为重要的大型矿聚集区,其主要的产铀花岗岩体是诸广山岩体和贵东岩体,均为多期多阶段的复式岩体,主要以印支期和燕山期的花岗岩为主。粤北地区的铀矿床主要由诸广山的长江铀矿田、澜河铀矿田、鹿井铀矿田和贵东岩体的下庄铀矿田组成,根据铀的成矿特征可分为硅化带型、交点型和碱交代型。粤北地区的铀成矿流体主要来自于地幔,而不是以往认为的花岗岩浆期后热液,铀源主要是粤北产铀岩体的印支期花岗岩。因此在华南开展新一轮铀矿找矿时,跳出以往“沿带找矿”的老思路,聚焦于印支期岩浆作用与铀矿床的关系,并重点关注华南地区可能的地幔柱或热点区域。     

北秦岭中生代沙河湾岩体环斑结构特征及有关问题的讨论

该岩体的环斑结构主要发育于边部含巨斑状黑云角闪石英二长岩中 ,环斑长石粒径一般 2cm× 4cm。形态多呈自形、半自形 ,有些为卵形。环斑长石由核部钾长石和多层或单层斜长石外壳两部分构成。钾长石内核呈肉红色 ,一般是由单颗粒组成 ,具卡氏双晶 ,普遍发育规则的条纹结构 ;中心部分钾长石分子含量Or为 95 ,边部为 84。外壳斜长石牌号一般为An2 0± ,为奥长石。内核和外壳中均发育石英、斜长石、黑云母、角闪石等矿物的包裹体 ;包裹体在其边部较多 ,中部较少 ,钾长石斑晶中的石英包裹体呈不规则的凹面状和水滴状。岩石中主要矿物具有 2个世代。这些特征显示 ,沙河湾岩体中的环斑结构与典型的环斑结构是相同的。亦表明典型的环斑结构可以出现于不同的时代和构造环境。由于其形成时代和产出背景不同于典型环斑花岗岩 ,该岩体属典型环斑花岗岩还是一种新的似环斑花岗岩还有待于进一步研究。     

招平断裂带中段深部结构构造——来自地震剖面的证据

玲珑花岗岩岩基东侧的招平断裂带是胶西北矿集区的主要控矿构造之一。布设于招平断裂带中段大尹格庄矿区的地震剖面,揭示了招平断裂带中段深部的结构构造特征,地震剖面显示,玲珑岩基内部有多个类似"拱弧构造"的岩浆侵入形成的弧形界面,由此推测存在2~3期的岩浆活动。剖面显示了3期构造组合样式,第1期为以招平断裂带和宋家河断裂为组合倾向SE的铲式断裂,底部似汇入统一的构造滑脱带;第2期为倾向NW的错断了招平断裂带的反倾伸展断裂;第3期为NE向延伸以花状构造为特征的走滑断裂。前两期反映构造发育处于伸展环境,第3期显示为左行走滑。招平断裂带深部延伸存在分支复合现象,形成由2个主裂面夹持的透镜状岩片。地震反射剖面数据的获得对深刻理解该区域中生代岩浆构造演化过程和深部找矿具有重要的借鉴意义。     

浙江沐尘石英二长岩体的岩石地球化学特征及构造意义

出露于江山-绍兴断裂带西南段东南侧的沐尘岩体,以发育暗色包体和环斑长石为特征,具有显著的岩浆混合作用.寄主岩为二长岩-石英二长岩组合,包体岩石为二长闪长岩.二长岩组合.造岩矿物有钾长石、斜长石、石英、普通角闪石和黑云母.岩石富碱(Na2O K2O=6.58%～10.42%,平均8.41%)、高钾(K2O/Na2O=0.72～1.45,平均1.16)、贫钛(TiO2=0.37%～1.22%,平均0.76%)、富集大离子亲石元素和轻稀土元素,具有钾玄质系列的岩石地球化学特征.该岩体侵位于后碰撞弧构造环境,是早白垩世早期该区重要的构造.岩浆热事件的产物.     

内蒙古苏尼特左旗地区堆晶角闪辉长岩的发现及地质意义

通过详细的野外工作和室内研究，发现苏尼特左旗附近较广泛地分布有一种主要由角闪石和外长石组成的堆晶岩，其化学成分属基性岩范畴，可定名为堆晶角闪辉长岩。这类岩体具清楚的层状构造、堆晶结构．岩石化学成分、稀土元素、结构和构造等特征均表明，该类岩石是由富水的拉斑玄武岩浆经分离结晶作用形成的，是造山带火成岩组合中的一个主要组成部分，形成于造山构造岩浆旋回的早期阶段。     

Advective heat transfer and fabric development in a shallow crustal intrusive granite — the case of Proterozoic Vellaturu granite,south India

Syntectonic plutons emplaced in shallow crust often contain intermediate-to low-temperature deformation microstructures but lack a high-temperature, subsolidus deformation fabric, although the relict magmatic fabric is preserved. The Proterozoic Vellaturu granite emplaced at the eastern margin of the northern Nallamalai fold belt, south India during the late phase of regional deformation has a common occurrence of intermediate-to low-temperature deformation fabric, superimposed over magmatic fabric with an internally complex pattern. But high-T subsolidus deformation microstructure and fabric are absent in this pluton. The main crystal plastic deformation and fluid enhanced reaction softening was concentrated along the margin of the granite body. Resulting granite mylonites show Y-maximum c-axis fabric in completely recrystallized quartz ribbonds, dynamic recrystallization of perthites, and myrmekite indicative of fabric development under intermediate temperature (∼ 500–400°C). The weakly-deformed interior shows myrmekite, feldspar microfracturing and limited bulging recrystallization of quartz. The abundance of prism subgrain boundaries is indicative of continuing deformation through low-temperature (∼ 300°C). The relative rates of cooling influenced by advective heat transfer and deformation of the pluton seem to control the overall subsolidus fabric development. The rapid advective heat transfer from the interior in the early stages of subsolidus cooling was followed by slow cooling through intermediate temperature window as a well-developed phyllosilicate rich mylonitic skin around the granite body slowed down conductive heat loss. Low-T crystal plastic deformation of quartz was effected at a late stage of cooling and deformation of the shallow crustal granite body emplaced within the greenschist facies Nallamlai rocks.     

Magmatic structures in the Krkonoše–Jizera Plutonic Complex,Bohemian Massif: evidence for localized multiphase flow and small-scale thermal–mechanical instabilities in a granitic magma chamber

The present paper examines magmatic structures in the Jizera and Liberec granites of the Krkonoše–Jizera Plutonic Complex, Bohemian Massif. The magmatic structures are here interpreted to preserve direct field evidence for highly localized magma flow and other processes in crystal-rich mushes, and to capture the evolution of physical processes in an ancient granitic magma chamber. We propose that after chamber-wide mixing and hybridization, as suggested by recent petrological studies, laminar magma flow became highly localized to weaker channel-like domains within the higher-strength crystal framework. Mafic schlieren formed at flow rims, and their formation presumably involved gravitational settling and velocity gradient flow sorting coupled with interstitial melt escape. Local thermal or compositional convection may have resulted in the formation of vertical schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in magma pressure. After the cessation or deceleration of channel flow, gravity-driven processes (settling of crystals and enclaves, gravitational differentiation, development of downward dripping instabilities), accompanied by compaction, filter pressing and melt segregation, dominated in the crystal mush within the flow channels. Subsequently, magmatic folds developed in schlieren layers and the magma chamber recorded complex, late magmatic strains at high magma crystallinities. Late-stage magma pulsing into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final crystallization. We emphasize that the most favorable environments for the formation and preservation of magmatic structures, such as those hosted in the Jizera and Liberec granites, are slowly cooling crystal-rich mushes. Therefore, where preserved in plutons, these structures may lend strong support for a “mush model” of magmatic systems.