论藏东玉龙斑岩铜矿带岩浆侵入时代

本文综合了玉龙斑岩铜矿带花岗岩类的K-Ar年龄数据,首次提供了Rb-Sr等时线、~(39)Ar-~(40)Ar全熔融法和U-Pb等时线年龄,确证岩浆侵入时代在早第三纪始新世至渐新世期间,且可划分为早(52.0±2.8Ma)、中(40.1±1.3Ma)、晚(33.2±1.3Ma)三期。     

湘东赣西Cystophrentis的发现及岩关阶地层划分

<正> 湘东赣西早石炭世地层解放前几乎没有记载。1954年,廖士范等在茶陵潞水建立“大节湖灰岩”,划为下石炭统,与下伏的余田桥“系”(自下而上包括麻石岭段、煤炭冲段、井冲段、翻下段、荒塘段)为假整合接触。1963年刘亚光在萍乡麻山,1965年湖南区测队在株洲三望桥均找到珊瑚Pseudouralinia和腕足类,确定大节湖灰岩相当于湘中下石炭统     

论扬子古陆东南边缘造山带形成时代

对扬子古陆东南缘浅变质岩层、花岗岩类、构造变形特征研究表明：“板溪杂岩”不是早古生代到三叠纪形成的；而是元古代前震旦纪形成的。由“板溪杂岩”组成的造山带不是中生代板块碰撞的产物，而是元古代华南地体向杨子地体俯冲一碰撞形成的造山带。在后来的地质时期受邻区造山事件的影响，对本区构造起了改造作用。     

Homoceras带时代归属的讨论

关于Homoceras带的时代归属是有争议的,一种意见认为应属上石炭统底部(如石炭系三分则为中石炭统底部);另一种意见则认为应属下石炭统顶部,因此Homoceras带的层位问题,实质上牵涉到上、下(或下、中)石炭统的分界问题。本文对含Homoceras的广西南丹七圩和贵州水城德坞剖面作了分析,以Homoceras带菊石的壳铈变化、缝合线演变特征看,更接近于下石炭统的Eumorphoceras带。另外与Homoceras相共生的腕足类Gigantoproductus,Striatifera是典型的下石炭统化石,因而我国Homoceras带应置于下石炭统顶部。     

黔东南金矿形成时代的确定兼论湘黔加里东金矿带

黔东南金矿是赋存在新元古代浅变质岩系中的石英脉型金矿,变质岩的原岩是一套火山-沉积岩,由凝灰岩、凝灰质砂岩、粉砂岩等组成,多具清楚的条纹韵律结构,反映了一种浊流沉积的环境。石英脉的产出受背斜构造和剪切断裂控制,有整合层间脉与断裂破碎带充填脉两种类型。石英脉的组成比较简单,除石英外,主要是硫化物类矿物及捕获的围岩成分。通过对5个矿点的石英中包裹体的Rb-Sr同位素测定和等时线法定年,确定其成矿时代为加里东期,与比邻的湘西同类型金矿的形成时代一致。根据赋矿地层岩性、地质演化历史与构造环境的比较,圈划出了一个湘黔加里东金矿带,对今后的找矿工作会有参考价值。     

论滑坡的时代问题

正科学界定古滑坡、老滑坡和新滑坡的时代,既有理论意义,也有应用价值。基于形成时代的滑坡概念或术语定义原则应该是含义明确、科学有据、易于接受和便于应用。关于滑坡时代的认识已经历过相当长的时期。原苏联Ф.П.萨瓦连斯基(1932)、B.B.波波夫(1958)先后提出现代滑坡、老滑坡、古滑坡和埋藏滑坡的概念。卢螽槱(1984)提出古滑坡是在更新世或更早的时代曾有滑动,在现代已相对稳定的滑坡;老滑坡是已稳定的;新滑坡是正在活动的。胡广韬(1995)认为古滑坡发生于15万年以前;老滑坡发生于0.5~15万年之间;新滑坡发生于0.5万年以来。晏同珍(2000)认为古滑坡发生于更新世晚期及以前;老滑坡发生于全新世中早期;新滑坡发生于全新世晚期。     

论东河塘组的时代

东河塘组在塔里木盆地分布广泛，长期以来被视为早石炭世早期的沉积。近年来，开展了对巴楚小海子露头剖面和塔里木盆地沙漠覆盖区钻井剖面的深入研究，积累了大量资料。根据露头和井下东河塘组及其上覆、下伏地层层序的辨别和所含古生物化石的鉴定，认为东河塘组的地质时代应属于晚泥盆世，大致可与塔西南的奇自拉夫组进行对比。     

论官亭群的时代归属

官亭群一名最早由甘肃综合地质大队西秦岭地质队(1964)命名,命名地点在甘肃宕昌以南的通北口、甘江头、邓邓桥、官亭、秦峪、大峪一线,岩性为砂页岩夹薄层灰岩、角砾状灰岩,厚度大于6 320m,他们将其时代归为二叠纪—三叠纪。以后陕西区测队完成的1:5万武都幅(1971)、甘肃地质局所编甘肃区域地层表(1980)均沿用了官亭群一名,但总的来说对官亭群时代认识并不清楚。     

On the age of KREEP

Many lunar highland rocks have been extensively metamorphosed during the late heavy bombardment of the Moon 3.9–4.0 AE ago. Rubidium and other, more volatile elements were preferentially mobilized during this event, which resulted in a considerable scatter of RbSr model ages. This scatter can be considerably reduced by estimating the original Rb content on the basis of Sm or other, less mobile, incompatible elements. The principal uncertainty on the corrected model ages of 4.25–4.45 AE comes from the original Sm/Rb ratio.Highland rocks enriched in incompatible elements in most cases are mixtures between KREEP-basalt and other highland rock types. After corrections for Rb mobilization 3.9–4.0 AE ago, slight isotopic differences among KREEP-enriched rocks from different landing sites becomes noticeable. These differences correspond to different meteoritic groups as defined by Morgan et al. (1974). Apparently there existed slightly different KREEP basalt reservoirs, with formation ages ranging from 4.25 to 4.45 AE. These reservoirs were partly exposed through impacts of basin-forming planetesimals 3.9–4.0 AE ago. The resulting impact melts were contaminated with meteoritic material from the bombarding planetesimals.The $\text{4.63 ± 0.1}$ AE RbSr isochron of trace element poor highland rocks (Schonfeld, 1976) is determined by a K,Rb- and Ba-rich component, which formed earlier and independently of KREEP basalts.     

On the age of the Hoxnian interglacial

Fifteen new radiocarbon datings from British Pleistocene deposits are described. The datings are related to the classic Pleistocene succession and shown to be consistent with the stratigraphic sequence of East Anglia. On the basis of these datings, an absolute chronology is developed. According to this chronology, the glacial drifts of East Anglia ought to postdate 40,000 B.P. and hence belong to the Last Glaciation of the British Isles. The Hoxnian interglacial of this chronology is dated between about 25,500-21,000 B.P. The conventional age for the Hoxnian interglacial is 175,000–120,000 B.P. The validity of the radiocarbon datings is considered and some of the implications and problems of a revised age for the Hoxnian interglacial are reviewed.     

龙泉关韧性剪切带的新认识

龙泉关韧性剪切带五台山花岗岩－绿岩地体与阜平高级变质地体的接触部位，它不仅改造了“阜平群”而且也改造了“五台群”宏观构造，显微组构和矿物组合研究表明，龙泉关韧性剪切带经历了两期变形作用，早期发生于恒山古陆块－车厂弧地质体－阜平古陆块碰撞过程中，形成低角度逆冲型韧性剪切带，使地壳显著增厚，晚期发生于增厚同的纵向伸展过程中，使地壳得以均衡发展，形成低角度伸展型韧性剪切带，龙泉关韧性剪切带的变形特征反映     

On the age of the Kiruna Greenstones,Northern Sweden

Three types of zircons from an albite diabase sill within the Kiruna Greenstone Group have been investigated to determine their age and order of crystallization. The youngest, pink and transparent zircons probably crystallized in late fissures and in association with a thermal event. The intermediate, white zircon populations could not be readily dated because of significant lead loss. The lead 207/206 ages of both the pink and white zircons agree roughly with that of the Sm-Nd isochron (about 1.93 Ga) on secondary minerals from a Kiruna greenstone (Skiöld and Cliff). The oldest, brown zircons indicate an age of about 2.2 Ga, and probably reflect the initial crystallization of the rock. The formation of the early Proterozoic greenstones in the Kiruna area thus commenced about 2.2 Ga ago or earlier. These results are consistent with the proposed chronostratigraphy of the Jatulian formations in Finland (e.g., Simonen; Meriläinen). A time interval of at least 0.3 Ga is assumed for the volcano-sedimentary period which pre-dates the Svecokarelian orogeny of the Kiruna area.     

On the age of mylonites within the Mont Blanc massif

Abstract

Three generations of mylonites occur in the Mont Blanc Massif :

— the first one has produced mylonitic schists trending N20°E, of regional extension; the late Variscan Mont Blanc granite intruded these mylonites;

— the second one has affected large areas in the Mont Blanc granite, with the same N20°E direction;

— the third one is located along rather narrow bands N45°E, in the granite as well as in the older mylonitic schists.

All theses mylonites have been generated under (Bi) - greenschist facies conditions. They exhibit steeply plunging schistosity and lineation. They are all ante-Alpine; paradoxically, Alpine structures within the massif do not exhibit a striking appearence.     

论河北南部太原组的时代问题

<正> 近年来,本文作者在太行山东麓峰峰至元氏一带对晚古生代主要含煤地层作了比较系统的研究,采集了大量的动、植物化石,于原上石炭统太原组上部的野青灰岩层中,发现了大量二叠纪的非有孔虫Geinitzina,Pachyphloia,类Nankinella 及其砂泥岩夹层中发现常见于山西组、下石盒子组的Lobatannularia等植物证明了本区石炭、二叠系的界线应重新厘定,二叠系之底界应置于野青灰岩层之下。     

安徽庐枞火山盆地铀矿床类型研究

在收集整理前人成果基础上,着重分析了庐枞盆地铀成矿地质特征及地球化学特征。盆地内铀矿化与石英正长岩具密切时空关联,石英正长岩是与火山岩同源并有时空联系的潜火山岩;潜火山岩外带砂岩层间破碎带和贯通潜火山岩与砂岩的断裂及其旁侧裂隙密集带构造是主要控矿构造,隐爆角砾岩构造亦控矿;与铀矿物伴生的金属矿物为中低温热液矿床标型矿物,铀矿石伴生元素及矿床内普遍而强烈发育的硅化,与潜火山岩型金属矿床特征相似。认为火山盆地内铀矿床类型应归属于潜火山岩型矿床,并进而对今后的铀矿勘查工作提出了建议。