挪威某些铜镍矿石中单斜磁黄铁矿出溶体的退火和粗化

在挪威某些正岩浆铜镍矿床的矿石中，六万磁黄铁矿基质内的单斜磁黄铁矿叶片是高温时形成的磁黄铁矿固溶体在降温过程中出溶的产物。出溶叶片宽度和间距的加大、叶片的带状分布、楔形尖端、箱状扭曲和复杂叶片等结构，表明出溶产物在不高于单斜-六方转变温度（254℃）的条件下发生过显著的退火和粗化。重结晶的六方磁黄铁矿基质中所保存的单斜变种甚少，表明变质作用所引起的矿石重结晶，可使磁黄铁矿吸收其中的单斜出溶体而发生均匀化。     

陕西银硐子-大西沟菱铁银多金属矿床热水沉积岩相特征及成因

陕西银硐子 -大西沟特大型菱铁银多金属矿床赋存于中泥盆世吉维特期之上的热水岩相中,其微相可划分为热水同生沉积 -沸腾交代微相、热水同生交代微相、热水同生沉积微相、热卤水渗滤交代微相、热水混合沉积微相。热水沉积岩富Na、Si、Fe、Mg、Mn、Ba、Cu、Pb、Zn、As、Ag、B等。在热水沉积盆地中,由富Ba的硫酸质热水、富Fe碳酸质热水以快速化学沉淀方式发生同生沉积成矿作用形成重晶石、菱铁矿层。银多金属矿层是由不同成分、性状、富Na、B、Si的铝硅酸质、硼酸质热水与前两类热水相互混合而形成热水混合体系,这种非平衡体系发生了剧烈地化学反应而使矿质发生骤沉。     

Cikidang Hydrothermal Gold Deposit in Western Java, Indonesia

Abstract. The Cikidang gold deposit, discovered in 1991, is located within the Bayah dome, a Tertiary-Quaternary volcanic zone at west end of Java, which is well known as a gold district (e.g., Pongkor and Cikotok mines). Typical low-sulfidation quartz-adularia-sericite(-calcite) vein deposits represent the gold deposit in the district.
The Cikidang vein system comprises four sub-parallel quartz-adularia-sericite(-calcite) veins that are rich in manganese oxide and limonite with very poor amount of sulfides. These vary from 0.5 to 2.7 m thick and extend for up to 1,000 m long. The vein trends roughly N-S and dip 60 to 86° toward west. The ore grades vary from trace to 74.9 g/t Au and 1.2 to 225.0 g/t Ag. A K/Ar age determination on adularia yielded 2.4 Ma for the Cikidang vein.
The ore minerals are represented by electrum, argentite, aguilarite and pyrite. Electrum shows the compositional ranges of Ag (50–65 atom %). The gangue minerals are dominated by quartz with variable amounts of calcite, sericite, adularia, clay minerals, manganese oxide and limonite. The vein textures are so variable as banded, colloform, comb, brecciated and massive. Host rocks, composed of Miocene lapilli tuff and breccia, suffered from pervasive hydrothermal alterations. Wall rocks adjacent to the vein are characterized by argillic and propylitic alteration.
The fluid inclusion study of the Cikidang vein shows homogenization temperatures ranging from 170 to 260°C. Salinities are low, generally below 3 wt% NaCl equivalent. Oxygen isotope results suggest meteoric water in origin for ore fluids responsible for the Cikidang deposit.     

病态线性方程组的简单迭代解法

针对地球物理反问题中经常碰到的病态线性方程组的求解问题。本文提出了一种简单迭代（ＳＩ）算法,从理论上证明了解序列收敛且收敛到方程组的真解,然后给出了几个算例,将计算结果与对付病态问题能力很强的ＣＧ类算法的结果进行了对比,结果表明：ＳＩ算法具有极强的抗病态能力,计算精度明显高于ＣＧ类算法,但计算速度稍低于后者     

河南小秦岭东闯金矿床矿物标型特征研究

东闯金矿床为特大石英脉型金矿。通过对矿石中主要矿物黄铁矿、石英及自然金等的标型特征研究,探讨了矿床的成因及评价指标,认为金矿成矿与岩浆热液和老变质岩系（太华群）关系密切。     

Separation and Precise Measurement of Lithium Isotopes in Three Reference Materials Using Multi Collector‐Inductively Coupled Plasma Mass Spectrometry

Lithium separation technique for three reference materials has been established together with precise determination of lithium isotope using a Neptune multi collector-inductively coupled plasma mass spectrometry (MC-ICP-MS). The solutions of lithium element standard reference materials, potassium, calcium, sodium, magnesium and iron single element, were used to evaluate analytical methods applied. Three separate stages of ion-exchange chromatography were carried out using organic cation-exchange resin (AG 50W-X8). Lithium was enriched for the three stages using different eluants, which are 2.8 M HCl, 0.15 M HCl and 0.5 M HCl in 30% ethanol, respectively. The columns for the first and second stages are made of polypropylene, and those for the third stage are made of quartz. Total reagent volume for the entire chemical process was 35 mL for three reference materials. The recovery yielded for the three stages is 98.9–101.2% with an average of 100.0%, 97.6–101.9% with an average of 99.9%, and 99.8–103.3% with an average of 100.6%, respectively. The precision of this technique is conservatively estimated to be ±0.72–1.04‰ (2σ population), which is similar to the precision obtained by different authors in different laboratories with MC-ICP-MS. The δ7Li values (7Li/6Li relative to the IRMM-016 standard) determined for andesite (AGV-2) and basalt (BHVO-2) are 5.68‰ (n=18), 4.33‰ (n=18), respectively. The δ7Li value (7Li/6Li relative to the L-SVEC standard) determined for IRMM-016 is –0.01‰ (n=15). All these analytical results are in good agreement with those previously reported. In addition, the results for the same kinds of samples analyzed at the MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, are consistent with those obtained at the Plasma Laboratory, University of Maryland, within analytical uncertainty. According to these experiment results, it is concluded that this proposed procedure is a suitable method for determining the lithium isotopic composition of natural samples.     

1220铀矿田同位素地球化学和矿床成因研究

1220铀矿田分布于中生代后地台构造-岩浆活化带中1220破火山口周围。成矿过程中有三期热液活动和两期矿化作用。第一期是碱交代型矿他,第二期是萤石-水云母型矿化。将沥青铀矿的~(238)U/~(204)Pb—~(206)Pb/~(204)Pb等时年龄作为成矿年龄,它略低于火山活动年龄。通过氧、碳、硫、铅和锶同位素研究,对成矿溶液来源及演化、成矿过程和成矿物质来源等问题进行了探讨,得出了成矿溶液由岩浆水和大气降水混合组成,成矿物质主要来源于火山岩浆的结论。     

Zebra and boxwork fabrics in hydrothermal dolomites of northern Canada: Indicators for dilational fracturing,dissolution or in situ replacement?

Zebra and boxwork fabrics in Manetoe and Presqu'ile hydrothermal dolomites provide critical data for discrimination between hypotheses for their origin. In a unique occurrence, sets of weakly imbricated, decimetre‐sized curvilinear lenticles of white dolospar are developed within sub‐metre sized tongues of greyish‐white dolomitized crinoidal packstone and grainstone. This nascent zebra fabric has developed along wavy to nodular intra‐bed sedimentary partings. Primary bedding can be traced through dolomitized masses containing these fabrics, into the surrounding undolomitized limestone. All zebra and boxwork fabrics are confined within single beds, consistent with an early burial time of origin. No change in bed thickness occurs across zebra or boxwork fabrics within beds; this indicates a dissolutional, rather than a dilational, origin for the creation of pore space partly cemented with white dolospar. The dolomitized groundmass displays an abruptly gradational or sharp transition to centripetal saddle dolomite cement, which partially to nearly completely, occludes vugs. Circulation of geothermally heated hypersaline Devonian Elk Point basinal sea water brines led to dissolution and replacive dolomitization of limestone adjacent to vugs, and near‐contemporaneous precipitation of white dolospar within dissolutional vugs, consistent with geochemical simulations. The presence of downward‐extending galleries of white dolospar‐cemented solution‐collapse breccia provides further support for an interpretation of regional thermally driven convection of hydrothermal evaporative sea water brines across a broad area of northern Canada. The absence of gases under pressure in vacuoles within fluid inclusions from Manetoe and Presqu'ile dolospars is also more consistent with a dissolutional and contemporaneous dolomitization origin for these fabrics, rather than an origin involving dilational fracturing for space creation and dolospar precipitation. The ubiquitous presence of zebra and boxwork fabrics in hydrothermal dolomite reservoirs indicates that they are not confined fault zones and instead occur wherever precursor limestones had relatively greater porosity and permeability prior to dolomitization.     

Transformation of magnetite to hematite and its influence on the dissolution of iron oxide minerals

Deformed rocks of the Itabira Iron Formation (itabirites) in Brazil show microstructural evidence of pressure solution of quartz and iron oxides; it appears that magnetite was dissolved and hematite precipitated. The dissolution of magnetite seems to be related to its transformation to hematite by oxidation of Fe²⁺ to Fe³⁺. The transformation of magnetite to hematite occurs along {111} planes, and results in the development of hematite domains along {111} that are parallel to the foliation. The difference in volume created by the transformation of magnetite to hematite and the shear stress acting on the interphase boundaries allow fluids to migrate along these planes. The dissolution of magnetite involves the hydrolyzation of the Fe²⁺—O bonds at interphase boundaries of high normal stress. The high fugacity of oxygen in the fluid phase promotes the reaction of Fe²⁺ (in solution) with oxygen. Fe²⁺ ions oxidize to Fe³⁺ and precipitate as hematite platelets with their longest axes oriented parallel to the direction of maximum stretching. The transformation of magnetite to hematite during deformation plays an important role in the fabric evolution of the iron formation rocks. The transformation along {111} creates planes of weakness that facilitate fracturing. The fracturing plus the dissolution result in a reduction of magnetite grain size, and the oriented precipitation results in layers of hematite platelets. These processes produce a new fabric characterized by a penetrative foliation and lineation.     

碱性溶液中坡缕石水解作用动力学实验研究

对安徽官山地区沉积型、热液型坡缕石进行碱性溶液中水解作用的动力学实验研究.结果表明:沉积型坡缕石较热液型更耐碱,且两种坡缕石均存在明显的差异溶解现象,即四面体硅的溶解速率要略大于八面体铝阳离子的溶解速率.碱溶液中沉积型、热液型坡缕石水解动力学均适宜采用圆柱体扩散控制模型模拟,其浸出率x对反应时间t的关系可表示为(1-x)+xlnx=kt.在实验条件下沉积型坡缕石水解过程中,Al3+和Si4+反应表观活化能分别为18.16 kJ/mol和18.53 kJ/mol.热液型坡缕石水解过程中,Al3+和Si4+反应表观活化能分别为31.2 kJ/mol和32.95 kJ/mol.