基于CWI方法的门源MS6.9地震余震定位研究

门源发生M_S6.9地震后,余震目录中含有大量的单台事件,为了解决单台事件的定位不准确性,利用尾波干涉(CWI)的震源定位方法将门源台记录到震后8小时内的101次单台事件进行重定位,该方法主要通过计算事件对尾波部分的间距不确定性矩阵,从而估计聚类中具有相似震源机制的地震事件对之间的间距,通过优化这些事件对的间距来解决聚类中一组事件的相对位置。最后,对定位结果进行评估,得到相对可靠的定位结果。     

西藏班公湖—怒江缝合带东段丁青蛇绿岩中的铬铁矿:产出特征与类型

丁青蛇绿岩体位于班公湖—怒江缝合带东段,该缝合带与雅鲁藏布江缝合带并列,是寻找我国铬铁矿床的重要地区。该蛇绿岩体呈近南东向展布,总面积近600 km2,主要由地幔橄榄岩、辉石岩、辉长岩、辉绿岩、玄武岩、斜长花岗岩、硅质岩和泥质岩组成。根据空间分布,丁青蛇绿岩分为东、西两个岩体。在前人工作基础上,通过地质填图、实测剖面、探槽和钻孔编录,共发现豆荚状铬铁矿矿点83处,其中东岩体27处,西岩体56处。根据铬铁矿产出和围岩特征,丁青铬铁矿可分为4种产出类型。类型I:矿体呈脉状产出,围岩为条带状或透镜状纯橄榄岩和块状方辉橄榄岩;类型II:矿体呈透镜状、豆荚状或不规则团块状产出,围岩为薄壳状纯橄榄岩和斑杂状或块状方辉橄榄岩;类型III:矿体呈浸染状弥散分布于纯橄榄岩中,围岩为条带状纯橄榄岩和块状或斑杂状方辉橄榄岩;类型IV:矿体呈条带状产出,围岩为条带状或透镜状纯橄榄岩和具定向结构的方辉橄榄岩。根据矿石构造特征,主要分为块状、脉状、浸染状、浸染条带状4种类型。块状和脉状铬铁矿为矿石的主要类型,少量为浸染状和浸染条带状,局部纯橄榄岩中发育极少量瘤状或豆状构造。本研究选择了13处代表性铬铁矿点开展了详细的岩石学、矿相学、矿物学和矿物化学等工作。根据矿石中铬尖晶石的矿物化学特征,可将丁青铬铁矿矿体分为高铬(Cr#=78～86)、中高铬(Cr#=60～74)、中铬(Cr#2=30～51)和低铬(Cr#=9～14)4种类型(Cr#=100×Cr/(Cr+Al))。丁青东岩体赋存有中高铬型和中铬型铬铁矿,缺少高铬型铬铁矿;西岩体赋存有高铬型和中铬型铬铁矿,缺少中高铬型铬铁矿。同时在丁青东、西岩体内均发现存在一种Cr#极低的铬铁矿,暂定为"低铬型铬铁矿"。这些不同类型的铬铁矿体与野外产出有一定的对应关系,也可能后者制约了它们的成因。与罗布莎岩体中的典型高铬型铬铁矿对比,丁青豆荚状铬铁矿在矿物组合和矿物化学成分等方面具有许多相似性,认为存在较大的找矿空间。     

基性-超基性侵入岩中-大比例尺专题地质填图实践——以塔里木板块东北部坡北岩体为例

目前,1∶5万地质填图规范中缺少对基性-超基性侵入岩填图方法的系统总结。以塔里木东北部坡北基性-超基性岩体为例,开展专题地质填图实践,在岩体地质、地球物理、遥感和地球化学综合调查的基础上,建立了科学问题、地质填图、矿床预测相结合的填图方法。将坡北基性-超基性岩体作为一个岩浆序列,根据岩浆性质与含矿性特征划分为2个岩浆亚序列,5个岩浆单元,分别对应不同的岩性组合。与岩浆亚序列相对应存在2类岩浆矿床,其中赋存铜镍矿化的岩相主要为橄榄岩相,含磁铁矿、钛铁矿的岩相主要与辉长岩、辉长苏长岩、辉石岩相有关。从野外踏勘、实测剖面等多个角度探讨了基性-超基性侵入岩1∶5万专题地质填图的方法,为此类工作提供了有益探索。     

场分立体显示系统的硬件实现

根据双摄像机的几何模型,提出了一套双眼立体显示系统的设计方案——场分立体视觉系统。硬件采用流行的ＰＣＩ总线与计算机相连,能够实时获取２个摄像机图像,并能按双眼成像要求的频率工作,产生一个增强的三维世界。     

华为P40手机北斗三频观测数据质量及噪声分析

研究华为P40手机终端北斗三频观测数据质量及噪声特性,通过与测量型接收机对比分析发现,P40手机海思芯片具有较好的北斗三号信号捕获能力,B1I、 B1C和B2a三频信号信噪比略低于测量型天线,且3个频点均存在与终端芯片相关的系统误差。外置天线零基线实验结果表明,P40手机海思芯片零基线定位精度达到mm级,伪距和载波相位噪声可达到测量接收机噪声精度水平,B2a伪距噪声优于0.5 m,3个频点的相位噪声均优于2 mm。     

Geochronology and Geochemistry of the Granite Xenolith within the Lamprophyre at the Zhenyuan Gold Deposit (Yunnan Province, SW China)

The xenoliths in host rocks of hydrothermal gold deposits can generally provide much geochemical information of the deep rocks, which may have an implication for the sources of ore-forming materials. Geochronology and geochemical characteristics are reported for a granite xenolith, which is enclosed by the lamprophyre in the Zhenyuan gold deposit (Yunnan Province, SW China). This granite xenolith mainly consists of K-feldspar, quartz, and plagioclase with trace amounts of magnetite, titanite, apatite, zircon, and sulfides. Zircons from the granite xenolith yield a weighted average U-Pb age of 281.1 ± 1.3 Ma (MSWD = 2.1), which could represent the crystallization age of this granite xenolith. The Ti-in-zircon geothermometer and the Mn concentration in apatite calculate that this granite xenolith formed at 685 ± 43°C with the logfO2 values ranging from NNO + 3.7 to NNO + 6.4. The zircons in the granite xenolith have a restricted range of positive εHf(t) values ranging from +9.4 to +10.8, and the corresponding Hf TDM2 model ages range from 588 to 678 Ma. The zircon U-Pb age and the Hf isotopic compositions indicate this granite xenolith within the lamprophyre is mainly derived from partial melting of juvenile crustal rocks before the completed closure of the Ailaoshan Ocean. The pyrites in the granite xenolith have higher Bi concentrations, and lower As, Sb, and Tl concentrations than the gold-bearing pyrites of the ores in the Zhenyuan gold deposit. The low Au concentrations of the pyrites together with the ore-forming age of the Zhenyuan gold deposit (Oligocene) indicate the granite xenolith may have limited contribution to the gold mineralization of the Zhenyuan gold deposit.     

甘肃龙首山东段小口子镁铁-超镁铁质岩体岩石学、地球化学及年代学研究

阿拉善地块南缘龙首山地区以产出新元古代的金川铜镍硫化物矿床而著名,围绕金川矿床外围寻找铜镍矿一直备受关注。小口子镁铁-超镁铁质岩体位于龙首山东段,主要由蛇纹岩、单辉橄榄岩、橄榄辉石岩组成,岩体中局部发现了星点状硫化物,硫化物由黄铁矿、黄铜矿组成,没有发现铜镍矿体,仅有部分磁铁矿化,前人研究认为小口子岩体可能是金川铜镍矿床同期的岩浆事件产物。本次研究通过岩石地球化学研究显示,小口子岩体镁铁比值为5.31~8.74,高于一般赋存铜镍矿岩体的镁铁比值。样品球粒陨石标准化的稀土元素配分曲线为平坦型,稀土元素总量低,暗示岩石具有橄榄石堆晶特征;Sr,Nd同位素研究显示:ε_(Nd)(t)=6.09~7.77,指示岩浆源区为亏损型地幔特征;微量元素比值与同位素模拟计算结果指示母岩浆经历了微弱的中上地壳物质混染。岩体中单颗粒锆石U-Pb年龄为284.4±3.5Ma,结合区域地质对比,小口子镁铁-超镁铁质岩体的形成背景可能与古亚洲洋的闭合或俯冲之后的伸展作用相关。     

班- 怒带东段丁青蛇绿岩中镁铁质岩石年代学及构造背景

丁青蛇绿岩位于班公湖-怒江缝合带东段,分为东、西两个蛇绿岩体,丁青西蛇绿岩体缺乏基性岩年代学研究。对丁青西地质填图显示,蛇绿岩主要由方辉橄榄岩、纯橄榄岩、辉绿岩、玄武岩及辉长岩组成。其中玄武岩、辉长岩及辉绿岩出露在宗白区域,玄武岩和辉绿岩与下侏罗统沉积岩呈构造接触,辉长岩呈岩脉侵入到下侏罗统沉积岩中。岩石地球化学研究表明,玄武岩和辉长岩同属于碱性基性岩石,其中玄武岩具有典型洋岛玄武岩的稀土和微量元素特征,可能形成于与地幔柱有关的洋岛环境。在玄武质凝灰岩中挑选出的锆石测年,获得U-Pb年龄为198.7±3.8Ma,属早侏罗世。辉长岩的稀土和微量元素含量低于典型洋岛玄武岩,但其REE和微量元素具有OIB的特征,与典型OIB相比,辉长岩的HREE发生了一定程度富集。辉长岩锆石的U-Pb年龄为164.3±2.6Ma,认为辉长岩在形成过程中受到了软流圈地幔和岩石圈下部LVZ中富集熔体的共同作用,其形成于大陆边缘裂谷环境;辉绿岩成分属于拉斑系列岩石,其REE和微量元素曲线显示辉绿岩同时具有N-MORB和E-MORB的特征。辉绿岩锆石U-Pb年龄为114.2±1.3Ma,其形成晚于玄武岩。结合区域地质,认为辉绿岩形成于受地幔柱影响的弧后扩张脊环境。本研究提供了丁青西蛇绿岩新的年代学和岩石学证据,为探讨丁青蛇绿岩的形成和演化历史提供了新的证据。     

Two‐Stage Sulfide Mineral Assemblages in the Mineralized Ultramafic Rocks of the Laowangzhai Gold Deposit (Yunnan,SW China): Implications for Metallogenic Evolution

The Laowangzhai gold deposit, located in the Ailaoshan gold belt (SW China), is hosted in various types of rocks, including in quartz porphyry, carbonaceous slate, meta‐sandstone, lamprophyre, and altered ultramafic rocks. In contrast to other wall rocks, the orebodies in altered ultramafic rocks are characterized by the occurrence of a large amount of Ni‐bearing minerals. The ore‐forming process of the orebodies hosted by altered ultramafic rocks can be divided into two stages: pyrite‐vaesite‐native gold and gersdorffite‐violarite stages. The contents of As and Sb increased during the evolution of ore‐forming fluid based on the mineral assemblages. Thermodynamic modeling of the Ni‐Cu‐As‐Fe‐S system using the SUPCRT92 software package with the updated database of slop16.dat indicates the fS₂ in ore‐forming fluid decreases significantly from stage I to stage II. The decreases of fS₂ due to crystallization of sulfides and fO₂ due to fluid–rock reaction were responsible for ore formation in altered ultramafic rocks of the Laowangzhai gold deposit. Geological evidence, the in situ sulfur isotope values of pyrite, and the other published isotopic data suggest that the ore‐forming fluid for ultramafic rock ores was dominantly composed of evolved magmatic fluid with the important input of sediments.     

Geochronology and geochemistry of the Huilvshan gabbro in west Junggar (NW China): Implications for magma process and tectonic regime

Mineralogy and Petrology - Gabbro plutons, consisting of clinopyroxene and plagioclase with trace amounts of magnetite, titanite, and apatite, intruded into Early Carboniferous volcanic-sedimentary...