江西大吉山五里亭花岗岩单颗粒锆石U-Pb同位素年龄及其地质意义探讨

江西大吉山五里亭花岗岩一直被认为是与大吉山钨矿有关的早阶段花岗岩体 ,时代为燕山早期。但实际上大吉山地区各阶段花岗岩体之间的时空关系并不清楚 ,前人的某些年龄数据也存在相互矛盾之处。本文利用单颗粒锆石 U - Pb化学法 ,对五里亭花岗岩进行了年代学研究 ,获得 2 38.4± 1Ma的岩体侵位年龄 ,这个年龄属印支期。本文还结合某些岩石学、地球化学特征研究及与相邻岩体的对比 ,认为五里亭花岗岩确应归属于印支期 ,因此 ,五里亭岩体与大吉山钨矿没有成因上的直接联系。五里亭花岗岩侵位年龄的厘定和该地区更多印支期花岗岩的不断发现 ,表明印支运动在华南的影响超出了人们以往的认识。在此基础上 ,本文还对华南印支运动和印支期花岗岩的问题进行了简单的讨论     

地质标本数字化实践研究新进展、问题与展望

地质标本作为地质历史和地学研究的见证物,是地质生产、研究与教学的核心材料和基础资源,是博物馆的立馆之本、服务之基,更是博物馆数字化的重点和难点。本文通过回顾总结中国地质博物馆十多年的数字化实践,以及横向对比国内外博物馆领域的数字化工作基础上,并结合测绘、光谱等领域的最新进展,进一步明确了数字标本的概念,数字标本的来源不局限于对现有标本的数字化,可超越传统标本尺度空间的限制,直接到标本采集点面向地质体进行无损采集,从而极大地开展标本采集、典藏、研究与科学传播工作。利用环拍-摄影测量法、矩阵拍摄法、拼接拍摄法等方法,对地质体进行大尺度的数字采集、后期加工形成数字地质体,因其具有地质体野外产出的空间关系、纹理特征、质地色泽等视觉特征,等同于在虚拟空间中再现了野外地质体,实现了地质体的数字化典藏,随着数字地质体的量的积累,孤立的地质体连成片,理论上讲可以实现典藏地壳。数字地质体不仅具有对已有地质体的数字化保护意义,而且具有科研、科普价值。自主研制的地质标本三维影像获取系统基本上解决了地质标本三维数字化存在的表面纹理信息清晰度低、高光材质及透明材质效果差、后期人工干预工作繁琐与艰巨这三个关键问题。最后,指出了当前数字标本正经历着由三维到多维的蝉变,综合分析了现代信息提取技术获取蕴藏在实体地质标本中专业信息的可行性,展望了多维数字标本实现的技术手段及其应用前景。     

中俄蒙毗邻地区主要金属矿产分布特征

通过介绍中俄蒙毗邻地区区域地质背景、成矿区划及区内金、银、铜、铅锌、铁等主要金属矿产资源概况,归纳总结了该区主要金属矿床的时空分布特征:金属矿床分带特征明显,成矿时期集中于燕山期,成矿作用主要与蒙古-鄂霍次克构造带拼合-碰撞造山作用有关.     

西范坪铜矿成矿作用初步研究——兼论还原硫对斑岩铜矿成矿的制约

对西范坪斑岩铜矿的蚀变作用、流体包裹体特征等进行了研究,指出该矿床是由两期岩浆流体叠加作用所形成的.第一期热液作用形成了磁铁矿化和黑云母化,并形成了无矿石英脉;第二期热液形成了阳起石化;早晚两期热液的混合引起了钾长石化及强烈的矿化.由于第二期流体的叠加,将还原硫(H2S)带到浅部,并与第一期富铜的高盐度流体相混合,从而形成铜硫化物的沉淀.第二期富含还原硫流体的加入,是西范坪斑岩铜矿床形成的重要控制因素之一.     

富钆镝易解石的发现

该矿物产于铀钍混合矿化的中粗粒黑云母花岗岩中。本文研究了产状、共生矿物、结晶特性、物理及化学性质并与易解石、钍易解石、铀易解石、钇易解石等作了对比。该矿物铀、钍、铅等含量均较高,在稀土含量中,钆、镝含量高达稀土总量的27％,故定名富钆镝易解石。     

横断山不同成因类型花岗岩类岩石中黑云母的标型特征

本文研究了横断山区不同成因类型花岗岩类岩石中黑云母的化学成分、微量元素、结构和物理性质等。结合花岗岩类岩石的成因类型,将黑云母分为三个亚种:富镁黑云母(MF=1.3—1.5)、镁黑云母(MF=1—1.3)和富铁黑云母(MF=0.5-1)。     

Mechanism and Modes of Microbial Minerogenesis of Polymetallic Nodules on the Ocean Floor

This paper presents a quantitative analysis of the relations of the occurrence of polymetallic nodules with the geochemical actions of microbes in the seawater, pore water and sediments at the bottom of the eastern Pacific Ocean basin. Emphasis is laid on the relations of the activity intensity and biochemical transformation rate of aerobic bacteria (iron bacteria, Thiobacillus thioparus, halobacteria and manganese-oxidizing bacteria) and anaerobic bacteria (sulphate-reducing bacteria, denitrifying bacteria, Thiobacillus denitrificans) with mineralization. The experimental research on the migration and accumulation of ore-forming elements caused by microbial and chemical actions shows that the microbes have changed the conditions of oxidation and reduction in the system, and their effect on the element precipitation is much stronger than the chemical actions and accelerates the enrichment of Fe and Mn. It demonstrates that the microbes can change the environment to promote the accumulation of ore-formin     

Five-Stage Model of the Palaeozoic Crustal Evolution in Xinjiang

The great majority of the Palaeozoic orogenjc belts of Central Asia are of the intercontinental type, whose evolution always follows a five-stage model, i.e. the basal continental crust-extensional transitional crust-oceanic crust-convergent transitional crust-new continental crust model. The stage for the extensional transitional crust is a pretty long, independent and inevitable phase. The dismembering mechanism of the basal continental crust becoming an extensional continental crust is delineated by the simple shear model put forward by Wernike (1981). The continental margins on the sides of a gently dipping detachment zone and moving along it are asymmetric: one side is of the nonmagmatic type and the other of the magmatic type with a typical bimodal volcanic formation. In the latter case, however, they were often confused with island arcs. This paper discusses the five-stage process of the crustal evolution of some typical orogenic belts in Xinjiang.     

Accelerated Exhumation During the Cenozoic in the Dabie Mountains: Evidence from Fission-Track Ages

Zircon and apatite fission-track dating indicates that the exhumation of the Dabie Mountains tended to be accelerated in the Cenozoic and that the exhumation of the eastern Dabie Mountains was more and more intense from south to north, which is in accordance with the more and more intense dissection from south to north, as is reflected by the modern geomorphologic features of the Dabie Mountains. The accelerated exhumation during the Cenozoic was related to the high elevation of the Dabie Mountains resulting from Late Cretaceous-Palaeogene detachment faulting and subsequent fault-block uplift and subsidence. The average elevation at that time was at least about 660 m higher than that at the present. The intense exhumation lagged behind intense uplift.     

Laihunite—A new iron silicate mineral

Laihuite reported in the present paper is a new iron silicate mineral found in China with the following characteristics:

1. This mineral occurs in a metamorphic iron deposit, associated with fayalite, hypersthene, quartz, magnetitc, etc.
2. The mineral is opaque, black in colour, thickly tabular in shape with luster metallic to sub-metallic, two perfect cleavages and specific gravity of 3.92.
3. Its main chemical components are Fe and Si with Fe³⁺>Fe²⁺. The analysis gave the formula of Fe Fe _1.00 ³⁺ ·Fe _0.58 ²⁺ ·Mg _0.03 ²⁺ ·Si_0.96O₄.
4. Its DTA curve shows an exothermic peak at 713°C.
5. The mineral has its own infrared spectrum distinctive from that of other minerals.
6. This mineral is of orthorhombic system; space group:C _2h ^/5 ?P2₁/c; unit cell:α=5.813ű0.005,b=4.812ű0.005,c=10.211ű0.005,β=90.87°.
7. The Mössbauer spectrum of this mineral is given, too.