我国前寒武纪变质岩的构造特征

我国前寒武纪变质岩系的主要构造变形特征是:线型韧性剪切带及逆冲推覆构造发育,一般都遭受了多期变形、变质和强烈的构造置换作用,显生宙再造作用强烈,发育各种类型的穹隆构造。这些特征反映了前寒武纪地壳结构的不均一性和水平运动为主的构造体制.据构造置换、构造组合样式等划分出五种变质岩系构造类型,并对它们的制图原则和研究方法,作了相应的讨论。     

Internal structures and U–Pb ages of zircons from a tuff layer in the Meishucunian formation, Yunnan Province, South China

The Precambrian/Cambrian (PC/C) boundary is one of the most important intervals for the evolution of life, represented by prominent biological evolution from the first appearance of soft-bodied animals from the late Neoproterozoic to the sudden diversification of animals with mineralized skeletons in the Cambrian. In South China several areas contain many fossils and are well exposed, suitable for the investigation of PC/C boundary. However, geochronological relationships are still poorly known because of lack of combined detailed investigations of internal structures of zircons and in-situ U–Pb dating.We focus on the internal structure of zircons from a tuff layer within Bed 5 in the Meishucun section on which we undertook cathodoluminescence (CL) imaging and in-situ U–Pb dating with LA-ICP-MS and nano-SIMS. Over 600 zircons from the tuff layer were classified into three types based on their CL images: oscillatory rims, inherited cores and dull structures. U–Pb dating of the internal structure of the zircons by LA-ICP-MS clearly shows a distinct unimodal age population dependent on the structure: 531 ± 17 Ma for the oscillatory rims and 515 Ma for the dull structures. The clear oscillatory zonation, the prismatic morphology, and their occurrence indicate that the oscillatory rims were formed from felsic magmatism, and that the U–Pb nano-SIMS age of 536.5 ± 2.5 Ma records the depositional age of the tuff. Our results indicate that the PC/C boundary is situated below Bed 5, and therefore the bottom of Zone 1 (Marker A) is more appropriate for the PC/C boundary than is the top of Zone 1 (Marker B). The age of a positive anomaly (P2) in the early Cambrian is estimated to be ca. 536 Ma.     

大别山高压-超高压变质期后伸展构造格局

大别山高压、超高压变质期后构造格架的最显著特征是以罗田片麻岩穹隆为核部的多层伸展拆离滑脱带的发育,并由它们将超高压变质单元、高压变质单元和蓝闪－绿片岩单元分隔成垂向叠置的席状岩片,类似于变质核杂岩的基本结构样式。这种伸展构造格架制约了高压、超高压岩石的展布,而在较大榴辉岩体中保存的缩短或挤压组构则是以高压、超高压变质作用为标志的陆－陆碰撞事件的记录。正确地区分挤压组构与伸展组构是识别大别山带内高压     

河北省铁矿类型及勘查开发现状

河北省是我国重要的铁矿产地。全省铁矿可归纳为5种成因类型,即沉积变质型铁矿、岩浆岩型铁矿、矽卡岩型铁矿、沉积型铁矿和火山热液型铁矿。在对不同类型铁矿地质特征进行总结的基础上,对全省铁矿的资源勘查和开发利用现状进行了梳理,对河北省铁矿资源禀赋特征进行了分析,提出了铁矿勘查、开发及管理中的问题和建议。     

关于防洪调度智能决策支持系统的分析与设计

防洪调度智能决策支持系统（ＦＣＤＩＤＳＳ）是实现防汛指挥管理科学化和现代化的重要手段。通过对ＦＣＤＩＤＳＳ的分析。论述了ＦＣＤＩＤＳＳ的总体设计、模型库设计和知识库设计,提出了在进一小详细设计中应注意的问题。     

大别地块超高压变质省构造学--以东冲河为例

大别山英山县东冲河地区大比例尺（１∶１万）地质制图和详细构造解析指出,大别地块超高压变质省最明显的构造特征,是叠加在先期挤压组构上的伸展组构,区域上表现为古老变质核杂岩几何学型式及多层低缓角度伸展拆离带,因此,局部地区在平面和横过超高压变质省的地质剖面上看到的是由不同岩片组成的构造柱或堆垛,呈现出“假单斜”。野外和显微构造观察也表明,运用构造解析方法,可以在不同尺度上判别中朝克拉通与扬子克拉通碰撞过程（２４０～２１０Ｍａ）及超高压变质岩石折返初期产生的挤压组构、折返及抬升过程中形成的伸展组构、以及伴随超高压岩石减压退变质作用的硅铝壳岩石部分熔融作用。东冲河地区超高压岩石构造学特征为深入研究整个大别—苏鲁超高压—高压变质带的形成和折返动力学过程,提供了一个窗口,并证实了“原地”模式     

A petrogenetic study of the garnet pyroxenite enclaves in spinel peridotite,North Dabieshan,China

Recently, garnet pyroxenite enclaves within peridotites occurring near Raobazhai, Huoshan County, have been discovered. The garnet pyroxenite is small pods, decimeters in size, enclosed within intensively serpentinized peridotites. Major mineral components comprise: garnet (Prp_25–35), sodium augite (Jd_10–25) with a small amount of ilmenite. There are two stages of retrometamorphism: the retrogressive granulite facies mineral assemblage is superimposed by that of amphibolite facies. The host rocks of the garnet pyroxenite are spinel peridotites, including spinel harzburgite and lherzolite. Due to intensive serpentinitization, only 5%–40% of the relic olivine (Fo_92–93) are preserved. The orthopyroxenes are Mg-rich (En_87–93) with bending of cleavages and granulation at their margins showing intracrystalline plasticity. On the basis of garnet-clinopyroxene Fe?Mg exchange equilibrium geothermometry proposed by Ellis & Green (1979) and Krogh (1988)K _D=4.06–5.28;T=793–919°C,P=1.5 GPa are estimated for the garnet pyroxenite. It is inferred that the peridotites are mantle rocks about 60 km in depth. During the exhumation of the orogenic belt, it was tectonically emplaced into the lower crust in the solid state and then uplifted to the shallow depth. Obviously, this kind of garnet pyroxenite must be petrogenetically related to its host rock. The REE distribution pattern and the Ni?Co?Sc diagram reveal that they are chemically equivalent to the basaltic melt and ultramafic residua respectively derived from partial melting of mantle rocks.     

Extensional Tectonic Framework of Post High and Ultrahigh Pressure Metamorphism in Dabieshan, China

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｓｔｕｄｙｏｆｈｉｇｈ－ｐｒｅｓｓｕｒｅ（ＨＰ）ａｎｄｕｌｔｒａｈｉｇｈ－ｐｒｅｓｓｕｒｅ（ＵＨＰ）ｍｅｔａｍｏｒｐｈｉｃｒｏｃｋｓｉｓｏｎｅｏｆｔｈｅｍａｊｏｒｈｏｔｔｏｐｉｃｓｉｎｔｈｅｓｏｌｉｄｅａｒｔｈｓｃｉｅｎ...     

南海北部活动构造及其对天然气水合物的影响

海底天然气水合物与活动构造关系极为密切,随着近十几年来海底天然气水合物勘探与研究取得的重要进展,相关活动构造也正在逐渐受到关注。通过对断裂、地震、气底辟以及海底火山活动等构造活动的多种表现形式的研究,分析了南海北部活动构造的特征。在南海北部,存在北东向、北东东-东西向、北西向3组活动断裂,其中北西向断裂切割其他两组,形成最晚。这些活动断裂以继承性为主,北东向和北东东向断裂均为切割地壳或岩石圈的大断裂。南海北部的震中呈带状分布,在东部呈北东走向,而西部受红河走滑断裂的影响,震中整体为北西走向分布。气底辟是对天然气水合物形成有重要指示意义的构造,同断裂一样,气底辟为气源垂直向上移动至形成水合物的温压带提供了良好的通道。南海北部分布的火山岩由东到西顺时针旋转。从地震剖面可以看出,岩体明显受张性断裂控制。东部天然气水合物的分布受北西向活动断层的影响较大,而西部则与海底滑坡密不可分。