信阳群的解体及其大地构造意义

通过对原信阳群标准地层剖面的深入研究,查明该岩石—地层单位实属变形十分复杂的构造地层体。古生物资料表明,原信阳群南湾组确属中—晚泥盆世地层;而同位素定年结果则显示,原信阳群龟山组纯系前泥盆纪变质杂岩组成的构造地层体。据此,笔者认为原信阳群应解体。本文着重从岩石、构造分析入手,对新解体出的不同地质体分别就其地层涵义、构造归属作了较系统的论述,并扼要阐明各自发展演化的大地构造意义。     

广东莲花山燕山早期断裂动热变质带的基本特征及形成机制的探讨

莲花山断裂带是一条多期变形变质带。研究表明,该变质带既有某些区域变质作用的特征,又有明显不同之处。变质带明显受断裂带控制,切割地层界线,线型雁列,发育于地热异常高值区和应力集中带,温度梯度陡,变化快,变质相带侠窄。它不论在时空展市上,还是在形成机制上,都与断裂构造带密切相关,据此认为该期变质作用是在动力和热力都比较活跃的环境中形成,是温度、压力和构造应力综合作用的结果。     

The higher grade metamorphic zonation of the Sambagawa metamorphic belt in central Shikoku, Japan

The higher grade metamorphic zonation of the Sambagawa (= Sanbagawa) belt is established for the first time for the whole area of central Shikoku. As discontinuous reactions to define the isograd are absent, the metamorphic grade is primarily determined by the Mg-Fe partitioning between garnet and chlorite along representative traverses. However, for regional mapping, mineralogical features of the pelitic schists, such as using mineral assemblages of more than divariant equilibrium, the modal garnet to chlorite ratio, and the optical properties of chlorite, are employed as auxiliary criteria.
The presence of the highest grade mineral zone in the middle of the structural level is confirmed, but its spatial distribution is far more complex than hitherto accepted. Thermal axes are now confirmed at three different structural levels. A model is presented in which the stacking of thrust sheets of different grade took place while metamorphic reactions were in progress. Thermal readjustment brought a continuous metamorphic temperature gradient across and within the thrust sheets. Tectonic blocks of metagabbro and ultramafic rock were emplaced synchronously with thinning and subsequently also re-equilibrated. Local anomalies of metamorphic grade, represented by mixing of schists of different metamorphic grade, exist, but they are due to a later stage event.     

鞍本地区鞍山群变质矿物及变质作用

鞍本地区鞍山群变质岩出露区可分为鞍山、辽阳、本溪三个小区。所有的变质岩均属角闪岩相,从西向东,变质程度递增。三个小区最先出现的特征变质矿物分别是铁铝榴石、十字石和夕线石。退化变质作用由西向东递减,在东-西鞍山矿区已退变为绿片岩相,在绿泥片岩中普通角闪石仅作为残留矿物出现在绿泥石的核心。鞍山小岭子矿区有紫苏辉石、红柱石和尖晶石组合,它们是燕山期花岗岩围岩中的接触变质矿物。     

新疆贝勒库都克钾长花岗岩交代蚀变及锡矿化特征

贝勒库都克钾长花岗岩是一个富含Sn、As和F的岩体,具同熔型特征,是形成贝勒库都克锡矿的母岩.在岩体形成的后期,经历了钾化—钠化—云英岩化三个交代蚀变阶段.Sn、As等成矿、伴生元素的析出和富集发生在钠化和云英岩化两个阶段,形成了一定规模的锡矿床.     

太湖三山岛击变岩的发现及其意义

太湖三山岛击变岩,宏观特征表现为崩解裂理;微观特征出现石英颗粒的晶体弯曲、多组微页理的面型特征、机械双晶、震变玻璃、焦石英及柯石英相变产生的放射状裂隙等,是陨石撞击地表的一种特殊地质现象。它的发现,是太湖成因研究中的重要进展。     

新疆博罗霍洛山地区上志留统博罗霍洛山组沉积构造背景分析

新疆中天山西段的博罗霍洛山地区,在早古生代具有裂陷带性质。上志留统博罗霍洛山组形成于该裂陷带的最后闭合阶段,具有其特殊的形成时间和沉积特征。通过对该组地层的沉积学、岩石学及地球化学等方面的分析,本文较深入地讨论了其沉积环境及其沉积构造背景。认为该组岩石为浊流沉积物,其形成与活动性较强的大陆边缘区有着密切的关系,其陆源物质来源以当时存在于裂陷带以南的具有一定陆壳厚度和中等成熟度的“伊宁古陆”区为主。     

Petrology, geothermobarometry and C-O-H-S fluid compositions in the environs of Rampura-Agucha Zn-(Pb) ore deposit, Bhilwara District, Rajasthan

The massive Zn-(Pb) sulfide ore body at Rampura-Agucha in Bhilwara district, Rajasthan, occurs within graphitic metapelites surrounded by garnet-biotite-sillimanite gneiss containing concordant bodies of amphibolite. These rocks and the sulfide ores have been studied to estimate the pressure, temperature and fluid composition associated with upper amphibolite facies metamorphism. Geothermobarometric calculations involving garnet-biotite and garnet-hornblende pairs, as well as sphalerite-hexagonal pyrrhotite-pyrite and garnet-plagioclase-sillimanite-quartz assemblages indicate that the most pervasive P-T condition during peak of regional metamorphism was 650°C and 6 kb, and was attained between the first and second deformations in the region. Some temperature-pressure estimates also cluster around 500°C–5.1 kb which probably represent retrograde cooling during unloading. Consideration of devolatilization equilibria in the C-O-H-S system at the pervasive metamorphic conditions mentioned above shows that the metamorphic fluid was H₂O-rich ( ) but also had a substantial component of . and were the other important phases in the fluid. CO (X_CO = 0.002) and were the minor phases in the fluid. It is probable that a part of this aqueous fluid was consumed by re-/neocrystallization of hydrous silicate phases like chlorite during the retrogressive metamorphic path, so that fluid entrapped in quartz below 450°C was rendered CO₂-rich (Holleret al 1996).     

The influence of karst features on environmental studies in Turkey

 The carbonate rocks of Turkey, which underlie about one third of the country, possess major water resources with great potential for electricity generation and water supplies. The ongoing development of karst features, especially in the southern part of Turkey, demonstrates specific environmental problems that occur in many karst water supply projects. Karst aquifers, springs, sinkholes, dolines, poljes and other karst features are of great importance from the standpoint of karst water resources and environmental research studies. In karst regions, conservation and protection of groundwater resources for both qualitative and quantitative evaluations is possible only when the catchment area is determined accurately. Since the catchment area in karst terrains is not limited by the surface drainage boundaries and the groundwater flows through well-developed coduits or fissures, the equations used in non-karstic areas cannot be applied to such karstic regions. Studies on the development of karst features and its environmental impacts in Turkey are of recent origin. Therefore, many unreliable methods are being applied in karstic areas. For example, the use of "shallow holes or sinkholes and fault zones" for septic water waste disposal or as sewage by those who are not familiar with karst, sometimes causes very serious problems of extensive groundwater pollution. This paper discusses the development of different karstic features in Turkey and case studies on its environmental impacts. Received: 27 December 1995 · Accepted: 10 July 1996     

河南嵩县七亩地沟金矿床成矿流体来源及演化——来自矿床地质和流体包裹体的证据

河南省嵩县七亩地沟金矿床位于华北克拉通南缘的熊耳山地区。矿床赋存在中元古代熊耳群中酸性火山岩中,矿体严格受构造断裂带控制,主要呈脉状产出,矿石以石英脉型占主导,少量蚀变岩型;主要矿石矿物为黄铁矿、少量方铅矿、闪锌矿、黄铜矿等。围岩蚀变以硅化、绢云母化、绿泥石化和碳酸盐化为主。成矿过程从早到晚可分为3个阶段:石英-黄铁矿阶段、黄铁矿-石英-多金属硫化物阶段和石英-方解石阶段。不同成矿阶段的石英和/或方解石中广泛发育流体包裹体。早阶段和中阶段石英中CO_2型流体包裹体、NaCl-H_2O型流体包裹体、含子矿物流体包裹体均有发育,晚阶段方解石中主要发育NaCl-H_2O型流体包裹体。从早阶段到晚阶段,流体包裹体均一温度分别为254~397℃、221~397℃、162~237℃,盐度w(NaCleq)从早阶段的3.52%~21.88%和34.95%~45.33%双峰值,经中阶段的0.42%~13.83%和29.11%~42.48%双峰值,到晚阶段w(NaCleq)为0.35%~5.86%。CO_2型包裹体估算的早阶段和中阶段捕获压力为93~199 MPa和47~169 MPa,晚阶段NaCl-H_2O型包裹体估算的捕获压力为28~64 MPa,相应的成矿深度为3.4~7.2 km、1.7~6.2 km和2.9~6.5 km,指示成矿发生在地壳隆升过程中,区域应力场由挤压向伸展转变。流体沸腾作用是导致硫化物和金等成矿物质快速沉淀的主要机制,通过沸腾和大气降水的混合,成矿流体系统由富CO_2向贫CO_2流体演化,由变质流体向大气降水演化。