GEOCHEMICAL EFFECTS OF MAJOR ELEMENTS DURING FLUID-ROCKS INTERACTION IN MARINWOBO FAULT IN THE SOUTH MARGIN AREAS OF ALTAI MOUNTAINS

There are four types of metamorphic rocks in the Marinwobo fault, i. e, cataclasite, mylonite,mictosite and migmatitic granite, and the formation of these rocks is due to the progressive metamorphism of the pyroclastics. The fluids play a very important role in the metamorphic process of these rocks in the Marinwobo fault, the most important feature is that the fluids not only result in the migration of the major elements of the deformation rocks, but also result in the volume loss of the deformation rocks in the deformation process. Thus the migration laws of the major elements in different stages of the progressive metamorphic process are discussed according to mass balance equations. Finally, the quantitative analysis of the mass loss and volume loss of the different rocks the in Marinwobo fault is discussed in this paper.     

试述福建顺昌南舟萤石矿地质特征

顺昌南舟萤石矿位于顺昌县埔上镇南舟村境内，1996年福建省区域地质调查队开展1：5万埔上幅区调时发现矿体，后开展普查工作表明该矿床规模大、交通方便，易于开采，现已投入开发利用。南舟萤石矿成矿地质特征在闽北丰富的萤石资源中具有一定代表性。     

略阳煎茶岭铜镍硫化物矿床Re—Os同位素年龄及其地质意义

采用矿石Re-Os同位素方法对陕西省煎茶岭硫化镍矿床矿石进行了成矿年代学研究,获得了878士27 Ma(1σ)的等时线年龄,首次厘定了该矿床成矿时代为新元古代,成岩成矿基本同时.通过对878 Ma硫化镍矿石初始Re-Os同位素体系的γOs计算和Re/Os值分析表明,其yOs和Re/Os值变化范围大,深部条带状矿石的Re/Os值仅为0.05,yOs为-6.70;块状矿石的Re/Os值范围为4.24～24.43,γOs为-15.37～+280.65,说明成矿过程中有壳源物质的混染;两件样品的γOs为负值(-15.37,-6.70),可能指示其超镁铁质岩浆来源于Re亏损地幔.煎茶岭超基性岩体年龄及其镍矿石的Re-Os等时线年龄与扬子克拉通北缘火山岩浆活动时间相对应,它们是扬子克拉通西北缘晋宁期构造岩浆成矿作用的产物.     

Experimental evidence for diamond-facies metamorphism in the Dora-Maira massif

The peak metamorphic conditions of subducted continental crust in the Dora-Maira massif (Western Alps) have been revised by combining experimental results in the KCMASH system with petrologic information from whiteschists. Textural observations in whiteschists suggest that the peak metamorphic assemblage garnet+phengite+kyanite+coesite±talc originates from the reaction kyanite+talc↔garnet+coesite+liquid. In the experimentally determined petrogenetic grid, this reaction occurs above 45 kbar at 730 °C. At lower pressures, talc reacts either to orthopyroxene and coesite or, together with phengite, to biotite, coesite and kyanite. The liberated liquid contains probably similar amounts of H₂O and dissolved granitic components. The composition of the liquid in the whiteschists at peak metamorphic conditions, a major unknown in earlier studies, was probably very similar to the liquid composition produced in the experiments. Therefore, the experimentally determined petrogenetic grid represents a good model for the estimation of the peak metamorphic conditions in whiteschists. Experimentally determined Si-isopleths for phengite further constrain peak pressures to 43 kbar for the measured Si=3.60 of phengite in the natural whiteschists. All these data provide evidence that the whiteschists reached diamond-facies conditions.

The fluid-absent equilibrium 4 kyanite+3 CELADONITE=4 coesite+3 muscovite+pyrope has been calibrated on the basis of garnet and phengite compositions in the experiments and serves as a geothermobarometer for ultra-high-pressure (UHP) metapelites. For graphite-bearing metapelites and kyanite–phengite eclogites, forming the country rocks of the whiteschists, peak metamorphic pressures of about 44±3 kbar were calculated from this barometer for temperatures of 750 °C estimated from garnet–phengite thermometry. Therefore, the whole ultra-high-pressure unit of the Dora-Maira massif most likely experienced peak metamorphic conditions in the diamond stability field. While graphite is common in the metapelites, diamond has not been found so far. The absence of metamorphic microdiamonds might be explained by the low temperature of metamorphism, the absence of a free fluid phase in the metapelites and a short residence time in diamond-facies conditions resulting in kinetic problems in the conversion of graphite to diamond.     

The crustal fluid evolution and the causes of earthquakes(Ⅲ)

Ｔｈｅｃｒｕｓｔａｌｆｌｕｉｄｅｖｏｌｕｔｉｏｎａｎｄｔｈｅｃａｕｓｅｓｏｆｅａｒｔｈｑｕａｋｅｓ（Ⅲ）ＣＨＡＮＧ－ＦＡＮＧＸＵ（徐常芳）ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｌｏｇｙ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅｉｊｉｎｇ１０００...     

关于银山矿床成矿作用的几个问题——兼与《江西银山铜铅锌金银矿床》的作者商榷

银山多金属矿床是一个特大型火山—潜火山热液矿床,具有复杂的多期多阶段的成矿作用和有序的成矿分带。成矿作用主要为火山—潜火山热液作用,但在此之前,还经历了一期由韧脆性剪切带形成而引起的动力变质热液作用。根据矿体与3个旋回潜火山岩体的时空关系,火山—潜火山热液成矿作用又可分为两个成矿期和5个成矿阶段。矿床地质地球化学研究表明成矿作用在空间上具有定向迁移的特点,结合流体动力学计算机数值模拟认为定向迁移的根本原因是构造岩浆脉动和隐伏岩体形态产状。笔者认为,矿区深部可能有隐伏岩体,但对隐伏的斑岩铜矿床不应抱很大希望     

Deep structure of the northeastern Japan arc and its implications for crustal deformation and shallow seismic activity

Seismic tomography studies in the northeastern Japan arc have revealed the existence of an inclined sheet-like seismic low-velocity and high-attenuation zone in the mantle wedge at depths shallower than about 150 km. This sheet-like low-velocity, high-attenuation zone is oriented sub-parallel to the subducted slab, and is considered to correspond to the upwelling flow portion of the subduction-induced convection. The low-velocity, high-attenuation zone reaches the Moho immediately beneath the volcanic front (or the Ou Backbone Range) running through the middle of the arc nearly parallel to the trench axis, which suggests that the volcanic front is formed by this hot upwelling flow. Aqueous fluids supplied by the subducted slab are probably transported upward through this upwelling flow to reach shallow levels beneath the Backbone Range where they are expelled from solidified magma and migrate further upward. The existence of aqueous fluids may weaken the surrounding crustal rocks, resulting in local contractive deformation and uplift along the Backbone Range under the compressional stress field of the volcanic arc. A strain-rate distribution map generated from GPS data reveals a notable concentration of east–west contraction along the Backbone Range, consistent with this interpretation. Shallow inland earthquakes are also concentrated in the upper crust of this locally large contraction deformation zone. Based on these observations, a simple model is proposed to explain the deformation pattern of the crust and the characteristic shallow seismic activity beneath the northeastern Japan arc.     

福建行洛坑钨矿床白钨矿Sm-Nd等时线年龄及微量元素地球化学特征

行洛坑超大型钨矿床位于福建省宁化县东部,是武夷山成矿带内最大的钨矿床,具有储量大、品位低、黑钨矿与白钨矿资源量相近的特点。白钨矿作为含钨矿物,其形成年龄可以代表矿床的成矿时代,其地球化学特征反映了成矿作用环境和过程。文章在对行洛坑钨矿床钨矿脉特征、黑钨矿与白钨矿赋存状态开展调查的基础上,挑选白钨矿单矿物进行了Sm-Nd等时线测年和微量元素测试。研究结果显示,白钨矿结晶年龄为（142.6±2.8）Ma,略小于黑钨矿原位U-Pb年龄（150.5±8.1）Ma和石英流体包裹体Rb-Sr等时线年龄（147.5±2.9）Ma,与矿区隐伏岩体成岩年龄143.5~149.5 Ma在误差范围内完全吻合,也与矿物结晶世代关系吻合,都属于晚侏罗世的产物,说明钨成矿与隐伏岩体成岩近于同时或稍晚发生。白钨矿中微量及稀土元素特征显示第一世代成矿流体中Eu³⁺ < < Eu²⁺,指示成矿流体为还原性流体;第二世代成矿流体中Eu³⁺ > > Eu²⁺,指示成矿流体为氧化性流体。行洛坑钨矿成矿与华南中生代大规模成矿作用及其大地构造背景和动力学环境密切相关。     

试论大厂锡多金属矿田矿化蚀变分带特征

大厂矿田矿化蚀变分带特征十分明显, 在水平方向, 整个矿田可分为西、中、东３ 个矿带。西、东矿带主要产出锡石—硫化物型矿床, 围岩蚀变类型主要有硅化、钾长石化、电气石化、绢云母化、碳酸盐化等。中矿带主要分布矽卡岩型锌铜硫化物矿床, 并有锑钨石英脉型矿床叠加其上。整个矿田矿化蚀变分带又具明显的不对称性, 并且每一种矿化类型又表现出各自的分带特点。大厂矿田的总体矿化蚀变分带特征与传统的顺向或逆向分带不同, 反映了多成因、多期次叠加成矿及蚀变的特点     

区域成矿流体的形成与演化

成矿流体是富含挥发份、碱金属的含矿卤水 ,其中碱金属来源于岩浆热液、变质热液、海水及通过水岩作用从岩石中萃取等 ;而挥发份来源于地幔、水岩作用与有机质分解作用。成矿流体中的硫也是多来源的 ,硫的活度与氧逸度有关 ,高温还原环境H2 S的活度降低 ;成矿流体的同位素分馏与水岩作用强度有关 ,控制同位素分馏的基本因素是温度及水岩比值。根据成矿流体的成分及物理化学性质 ,可以分类为高温硅钾卤水、中温碳酸盐卤水及低温硫酸盐型卤水。成矿流体没有固定的来源 ,在一定地质条件下 ,任何来源的热水流体都可以形成成矿流体。控制成矿流体形成的主要地质作用是岩浆作用、变质作用、地热增温作用及构造作用等。文中根据地质作用类型对区域地质流体进行划分 ,可分为岩浆作用区域成矿流体 (以高温硅钾卤水为主 ,可以有高温到中低温的流体分带 ) ,沉积作用区域成矿流体 (以中低温碳酸盐及硫酸盐型卤水为特征 ) ,大洋盆地区域成矿流体 (与岩浆岩区域成矿流体类似 ,有高温到低温的流体分带 )和变质作用区域成矿流体 (变质程度不同而有不同的流体类型混合 )。