Microthermometric measurement of fluid inclusions and its constraints on genesis of PGE-polymetallic deposits in Lower Cambrian black rock series, southern China

Systematic microthermometric measurements of fluid inclusions in the PGE-polymetallic deposits hosted in the Lower Cambrian black rock series in southern China were performed, and the results suggest: (1) there exist two types of fluid inclusions. TypeⅠis of NaCl-H2O system with low-medium salinity, and its homogenization temperatures (Th) and salinities are 106.9- 286.4℃ and ( 0.8- 21.8) wt%NaCl eq. respectively; TypeⅡ is of CaCl2-NaCl-H2O system with medium-high salinities, and its homogenization temperatures and salinities range from 120.1℃ to 269.6℃ and ( 11.4- 31.4) wt%NaCl eq., respectively. The typeⅡ fluid inclusions have been discovered for the first time in this kind of deposits; (2) two generations of ore-forming fluids were recognized. Characteristics of fluid inclusions in the PGE-polymetallic ores and carbonate-quartz stockworks in the underlying phosphorites are almost of no difference, they may represent ore-forming fluids at the main metallogenic stage. The peak value of homogenization temperature of those fluid inclusions is about 170℃, while their salinities possess a remarkable bimodal distribution pattern with two peak values of (27-31) wt%NaCl eq. and (4-6) wt%NaCl eq. On the contrary, fluid inclusions in the carbonate-quartz veins in the hanging wall may represent ore-forming fluids at the post-metallogenetic stage. The homogenization temperatures and the peak values of salinities are mostly 130-170℃ and (12-14) wt%NaCl eq., respectively; (3) nobel gas isotopic composition analyses in combination with the microthermometric measurements of fluid inclusions suggest that the ore-forming fluids at the main metallogenetic stage were probably derived from mixing of basinal hot brines with the CaCl2-NaCl-H2O system and seawater with the NaCl-H2O system; (4) in the Early Cambrian, the basinal hot brines were trapped in the Caledonian basins, which were distributed along the southern margin of the Yangtze Craton, and where giant thick sediments were accumulated, and expelled and migrated laterally along the strata because of the pressure caused by overlying sediments. The basinal hot brines absorbed Ni, Mo, V, PGE from the surrounding rocks and were transformed into ore-bearing hydrothermal fluids with the CaCl2-NaCl-H2O system and medium-high salinities, then ascended along faults and mixed with seawater of the NaCl-H2O system, and finally PGE-polymetallic deposits or occurrences were formed in the black rock series.     

华南地区7-10月两类区域性极端降水事件特征及环流异常对比

利用1981—2016年7—10月中国753站逐日降水资料、气象信息综合分析处理系统（MICAPS）逐日站点降水资料、日本东京台风中心西北太平洋热带气旋（TC）最佳路径资料和NCEP/NCAR再分析资料集,分析了华南地区区域性日降水极端事件（RDPE事件）的统计特征及环流异常。根据华南地区RDPE事件的发生是否受热带气旋影响将其分为TCfree-RDPE和TCaff-RDPE两类事件,其中TCaff-RDPE事件占42%且集中发生在8月4—5候;TCfree-RDPE事件以7月发生频数最多,占其总频次的1/2以上。TCfree-RDPE事件发生时,华南地区受异常气旋性环流控制,来自西太平洋和中国南海的暖湿气流与北方冷气团在此汇合并形成一条狭长的水汽辐合带,低层辐合、高层辐散,显著强烈的上升运动为TCfree-RDPE事件的发生与维持提供了有利条件;与此同时,波扰动能量由高原东北侧及河西走廊地区向华南一带传播并在华南显著辐合,有利于华南上空扰动的发展和维持。TCaff-RDPE事件发生时,华南上空由低层到高层的斜压环流结构更为明显,异常上升运动更加强烈,热带气旋在其运动过程中携带了大量源自孟加拉湾、中国南海和西太平洋地区的水汽并输送至华南地区,水汽辐合气流更为强盛。同时,波扰动能量由高纬度地区沿河西走廊向下游传播,但在华南地区辐合不甚明显。两类极端事件发生时,加热场上的差异亦明显。华南及邻近地区上空的大气净加热及其南侧大范围区域的净冷却所形成的加热场梯度对TCfree-RDPE事件的发生有利。而TCaff-RDPE事件发生时,〈Q₁〉和〈Q₂〉在经向上由18°N以南、华南及其邻近地区、32°N以北呈负—正—负的异常分布型,正距平值更高,加热场梯度更大,有利于TCaff-RDPE事件的维持。这些结果有利于人们认识和预测华南区域性日降水极端事件的发生。      

华南地区定点形变预测指标建设

基于《中国震例》及其它相关资料,构建华南地区定点形变预测指标体系,分类整理形变干扰库和形变异常库,列举出部分预测效能较好的形变指标,结果表明：华南地区区分干扰和前兆异常的工作量较大,排除干扰后实际发生的前兆异常次数不多。各省均有少量测项对于台站周边200～300 km范围内ML4.5地震有较好的映震效果。华南地震预测指标体系开展的一系列建设工作,将对未来更有效更科学地利用前兆观测数据打下基础。     

三水盆地发现5000万年前化石

日前,中科院古脊椎动物与古人类研究所研究员经实地考察证实,广东三水盆地发掘出了华南首个5000万年前鸟化石,同期发现的还有2只青蛙化石、20余块5000万年前的骨舌鱼类化石以及完整的茂名无盾龟化石。“三水盆地发现的鸟化石,既是华南地区始新世又是中新世发现的第一块。”中科院古脊椎动物与古人类研究所研究员张江永评价认为,“2只青蛙化石是华南地区的首次发现,     

Comparison of different land-surface perturbation methods in short-range ensemble forecasts

为了比较不同陆面扰动方法对短时集合预报的影响,本研究设计了陆面模式扰动实验(LSMPE),初始土壤湿度扰动实验(ISMPE),陆面-大气耦合系数扰动实验(LCCPE)以及大气扰动对照实验(GEFSPE).结果表明,在三组陆面扰动实验中,LSMPE能代表最大的不确定性且误差最小;ISMPE的离散度要比LCCPE稍大,但是...     

华南地区中生代以来构造应力场的基本特征

本文认为,华南地区于燕山旋回中早期主压应力轴是北西——南东和北西西——南东东向的。燕山晚期以来,主压应力轴基本上是北东——南西和北东东——南西西乃至近东西向的。     

华南地区石炭纪海平面波动与沉积效应

根据华南地区上泥盐统一石炭系地层剖面．古生物．岩性岩相及区域性海进海退旋回沉积特征，可划分出四个海平面波动旋回。特别是一、二两个旋回，引起了一系列的沉积效应，如形成含煤岩系，生物演变等；第四个旋回表现相对较弱一些；第三个旋回则表现为广泛的白云岩化。这四个海平面波动旋回与澳洲、欧洲海平面波动旋回相对应．它们均受到晚泥盐世-石炭纪冈瓦纳大陆冰川旋回的影响。这四个海平面波动旋回对华南地区地层古生物，岩相古地理以及沉积矿产具有明显的控制作用。     

古代锡矿今何在：关于我国古代文明史上一大疑案的探讨

中原地区是我国古代青铜冶炼中心,却未见一处锡矿产地,当时炼锡原料从何而来,迄今仍为一大疑案。多数学者偏向源于华南,现知这里锡资源丰富,自然易圆其说,但也有认为就地取材于中原的,只是现今没有见到它的产地。笔者从锡矿的找矿前提分析,亦认为不能排除中原地区古时开采过,今后还找得到锡矿的可能性。