Magnetotelluric investigation of lithospheric electrical structure beneath the Dharwar Craton in south India:Evidence for mantle suture and plume-continental interaction

Broad-band and long period magnetotelluric measurements made at 63 locations along -500 km long Chikmagalur-Kavali profile,that cut across the Dharwar craton (DC) and Eastern Ghat Mobile Belt (EGMB) in south India,is modelled to examine the lithosphere architecture of the cratonic domain and define tectonic boundaries.The 2-D resistivity model shows moderately conductive features that intersperse a highly resistive background of crystalline rocks and spatially connect to the exposed schist belts or granitic intrusions in the DC.These features are therefore interpreted as images of fossil pathways of the volcanic emplacements associated with the greenstone belt and granite suite formation exposed in the region.A near vertical conductive feature in the upper mantle under the Chitradurga Shear Zone represents the Archean suture between the western and eastern blocks of DC.Although thick (-200 km) cratonic (highly resistive) lithosphere is preserved,significant part of the cratonic lithosphere below the western DC is modified due to plume-continental lithosphere interactions during the CretaceouseTertiary period.A west-verging moderately conductive feature imaged beneath EGMB lithosphere is interpreted as the remnant of the Proterozoic collision process between the Indian land mass and East Antarctica.Thin (-120 km) lithosphere is seen below the EGMB,which form the exterior margin of the India shield subsequent to its separation from East Antarctica through rifting and opening of the Indian Ocean in the Cretaceous.

EFFECTS OF TURBULENT COHERENT STRUCTURE ON PLUME DIFFUSION IN ATMOSPHERE BOUNDARY LAYER

The simulation tests of plume diffusion have been carried out in an open water channel,in which a Laser Doppler Velocitymeter,optical concentration measurement and flow visualization technology have been used.Through experiments and theoretical analyses,the effects of environmental wind field,surface roughness and discharge condition of elevated source on plume diffusion have been investigated.The plume dif- fusion mechanism has been elucidated reasonably,based on the turbulent coherent structure theory.

A Study of Plume Rise from Multi-tube Chimney and Types of Chimney Structure

This paper tries to determine the economical type of reinforced concrete chimney structure based on the same effective height of chimney. The simulated experiments of wind tunnel are performed for the study, which compare multi-tube chimney with single tube chimney based on the same buoyancy flux of plume. According to the comparison among the experiment results and the previous study of plume rise, the paper defines some final plume rise models. Finally, the paper gives the cost-benefit analysis after making cost estimation for different types of chimney structure and recommends the economical and reasonable type of chimney structure in light of the same environmental benefits.

Characteristics of mantle branch structure in western Shandong and its roles in minerogenesis and ore-controlling

This work deals with the characteristics of mantle branch structure in western Shandong Province, China, with respect to the distribution characteristics and ages of the regional strata, the development of ring-like and radial faults, the development of gently inclined detachment-slip structures in the axial part, mantle-source magmatic activities, regional petrology, petrochemistry and isotope geology. The study indicated that the N-W sharply plunged ductile shear zone in the region of western Shandong cuts through the mantle rocks detached from the deep-seated North China mantle sub-plume, hence leading to unloading in response to depressurization and thereafter the formation of anatexis magma. The intense and complete magmatic evolution series not only manifests a variation trend of alkalinity of magma from high to low and its intrusive depth from deep to shallow, but also reflects that the wall-rock alteration shows a general evolution trend from strong to weak. The evolution of mantle structure played an important role in controlling endo-mineralogenesis, accompanied with the rise of the country rocks. As a result, typical mantle branch structures were formed as observed in western Shandong. At the top of the mantle branch structure was developed an obvious detachment-tilt fault block, and some endogenic ores, at the same time, were uplifted onto the shallow levels.

Cascaded Evolution of Mantle Plumes and Metallogenesis of Core- and Mantle-derived Elements

Mineral deposits are unevenly distributed in the Earth's crust, which is closely related to the formation and evolution of the Earth. In the early history of the Earth, controlled by the gravitational contraction and thermal expansion, lighter elements, such as radioactive, halogen-family, rare and rare earth elements and alkali metals, migrated upwards; whereas heavier elements, such as iron-family and platinum-family elements, base metals and noble metals, had a tendency of sinking to the Earth's core, so that the elements iron, nickel, gold and silver are mainly concentrated in the Earth's core. However, during the formation of the stratified structure of the Earth, the existence of temperature, pressure and viscosity differences inside and outside the Earth resulted in vertical material movement manifested mainly by cascaded evolution of mantle plumes in the Earth. The stratifications and vertical movement of the Earth were interdependent and constituted the motive force of the mantle-core movement. The cascaded evolution of mantle plumes opens the passageways for the migration of deep-seated ore-forming material, and thus elements such as gold and silver concentrated in the core and on the core-mantle boundary migrate as the gaseous state together with the hot material flow of mantle plumes against the gravitational force through the passageways to the lithosphere, then migrate as the mixed gas-liquid state to the near-surface level and finally are concentrated in favorable structural expansion zones, forming mineral deposits. This is possibly the important metallogenic mechanism for gold, silver, lead, zinc, copper and other many elements. Take for example the NE-plunging crown of the Fuping mantle-branch structure, the paper analyzes ductile-brittle shear zone-type gold fields (Weijiayu) at the core of the magmatic-metamorphic complex, principal detachment-type gold fields (Shangmingyu) and hanging-wall cover fissure-vein-type lead-zinc polymetallic ore fields (Lianbaling) and further briefly analyzes the source of ore-forming material and constructs an ore-forming and -controlling model.

Study on the Metallogenetism of Sub-mantle Plume and Mantle Branches in the Gold Mineralization Concentration Area of Northwest Jiaodong Peninsula

The northwest of Jiaodong peninsula is characterized by its greatest gold concentration area, enormous gold reserves and limited time interval （115±5Ma） of gold mineralization in China. Studies show that the east area of north China began its mantle plume evolution since the Yanshanian movement, and the Laiyang sub-mantle plume and its surrounding mantle branches such as those in Guojiadian, Aishan and Panshidian were formed in the mineralization concentration area of northwestern Jiaodong peninsula. With the development of mantle plume →sub-mantle plume → mantle branch→ favorable expending structures, the deep-derived hydrothermal fluid moved up to the favorable places, such as brittle-ductile or ductile-brittle shearing zones, the internal and external contact zones of intrusions, dense fracturing zones and the contact zones between dikes and countryrocks, and concentrated into deposits. Then the gold mineralization concentration zones that are centralized on mantle branches were formed. This study takes Guojiadian mantle branch as an example to discuss their metallogenetism and conclude the metallogenetic mode.

气液两相气泡羽流结构特征分析

气泡羽流的流动特性对气液传质及工业应用至关重要。对牛顿流体和非牛顿流体体系中气泡羽流运动特征进行综合分析。结合气液两相流动理论,阐述了全混气液体系水力学特性和羽流结构特征。分析全混气液体系中不同气相条件和液相性质下气泡羽流特征。结果表明:随着气相表观气速的增加,气液体系的水力学特性参数增加;随着液相质量分数的增加,气液体系水力学特性参数均降低。

场致发射电推力器羽流分布特性仿真

场致发射电推力器(FEEP)是微型电推进装置的典型代表。为深入理解结构参数对推力器性能的影响机制,本文采用PIC粒子模拟方法进行泰勒锥射流纳米尺度结构至宏观毫米尺度结构的羽流场仿真,并分析结构参数变化导致的羽流形貌差异及其对推力器性能参数的影响。研究结果表明:发射极高度是决定推力器束流是否会分叉的关键参数,低于300μm的发射极高度易于导致束流分叉并严重影响推力器性能和寿命;引出栅极槽宽是决定束流发散角和推力比冲性能的关键参数,其影响幅值可达30%~50%,羽流发散角随槽宽增加而增大,推力比冲随之减小;发射极-引出栅极间距对推力器性能影响相对较小,可在较大范围内支持推力器稳定高效工作。根据FEEP推力器性能随结构参数的变化规律,建议结构参数取值范围为:发射极高度500~1000μm,引出栅极槽宽2000μm左右,发射极-引出栅极间距360~1300μm。

幔壳运动及其成矿控矿作用——以小秦岭幔枝构造北矿带成矿控矿作用为例

燕山运动中晚期,华北东部地区进入了以伸展构造为主的地幔热柱演化阶段,小秦岭矿集区形成了典型的幔枝构造体系。深源含矿流体通过地幔热柱—地幔亚柱—幔枝构造,迁移到幔枝构造有利构造部位集聚成矿。北矿带是小秦岭幔枝构造主要成矿区之一,进入燕山运动晚期,幔枝构造中断裂活动相当强烈,同时沿断裂形成了一系列大型—超大型金矿床,以及多金属矿床。在众多成矿控矿因素中,区域性断裂构造应是重要的主导性因素,它们不仅是成矿流体的运移通道,而且往往成为重要的成矿储矿有利空间。特别是近年来深部地质勘查发现,地表沿区域性主干断裂展布的若干个大中型金矿,在一定深度上其成矿蚀变构造带却是串连在一起的,整个沿断裂展布的若干个大—中型金矿统称为某某某超大型金矿。每个区域性深大断裂控制着一个超大型金矿带。其形成超大型金矿的过程可以概括为:强烈的岩浆—变质杂岩上涌(隆)→上部盖层向外拆离滑脱→幔枝构造逐渐形成→断裂构造体系由压扭性转变为张扭性→含矿流体沿断裂贯入→成矿物质冷却结晶→形成超大型金矿的模式。

阜平—五台幔枝构造的时空结构及其对区域岩浆与金属成矿的控制作用

幔枝构造是牛树银团队提出的地幔热柱的第三级构造单元,很好地解释了华北地区内生金属矿床的时空分布规律,并在地质找矿中得到进一步的实践和证明。对位于太行山中—北段和五台山—恒山地区的阜平—五台幔枝构造的三维空间、形成时代、成矿特征与控矿作用进行讨论,并建立了其成矿系统模型,为区域找矿勘查提供技术支撑。

Spiral plume structures in turbulent natural convection between two vertical walls

By means of direct numerical simulation, coherent structures are investigated in turbulent natural convection between two vertical differentially heated walls. It is observed that large-scale spanwise vortices and spiral plume structures exist together in the flow. Spiral plume structures appear at the positions with relatively large helicity, large normal vorticity and high fluctuating temperature. In this note, the shape, the characteristics and formation of the spiral structures are studied and compared with those in Rayleigh-Benard convection. The conditional sampling analysis indicates the main properties of the spiral structures.

Hyperextended crustal structure of the Qiongdongnan Basin and subsequent magmatic influence from the Hainan mantle plume

The Qiongdongnan Basin(QDNB)is a rift basin located in the extension direction of the oceanic ridge of the Northwest Subbasin of the South China Sea.This basin is surrounded by Late Cenozoic Ocean Island Basalts(OIBs)magmatism associated with the putative Hainan mantle plume.However,how the Hainan mantle plume has affected the QDNB has not been studied in detail.To reveal the crustal structure of the QDNB and the possible influence of the Hainan mantle plume,we conducted a wide-angle seismic exploration from Hainan Island across the QDNB to the Xisha Block,and obtained the crustal structure by travel-time tomography.The results show that the crustal stretching factors of the Northern and Southern Rises of the QDNB are estimated to be 1.3-2.0,indicating slight or moderate crustal thinning.Whereas,the crustal stretching factor in the Central Depression of the QDNB is estimated to be more than 3.0,which means that the crust has been hyperextended.Controlled by two detachment faults(F2 and F11),the upper and lower crust show brittle and ductile thinning,respectively.Three anomalous low-velocity conduits penetrating the crystalline crust are developed in the Songnan Uplift and the Southern Rise of the QDNB.Their P-wave velocities are 5.5-6.0 km s^(−1),which are significantly lower than those of the surrounding crust(6.0-6.8 km s^(−1)).The Late Cenozoic magmatic intrusions(e.g.,sills and dikes)and hydrothermal activities can be observed in the sedimentary strata above these low-velocity conduits.We interpret that the low-velocity conduits might be the crustal magmatic footprints of the Hainan mantle plume,due to the correlated distributions of OIB-type magmatism,the magmatic intrusion patterns,the deep structure of the Hainan mantle plume and the high heat flow of 95 mW m^(−2).Thus,we propose that the crustal structure of the QDNB is the product of crustal hyperextension in the rifting stage and subsequently affected by the Hainan mantle plume magmatism.This study provides a typical case for understanding the influence of a mantle plume on the continental crust with pre-existing rift structures.

冀东峪耳崖金矿成矿地质环境及形成机制

冀东地区金矿集区是中国金矿主产地之一,文章以冀东地区峪耳崖金矿为例,探讨了陆壳深断裂岩浆活动下的峪耳崖金矿成岩成矿和形成机制,对峪耳崖金矿成矿地质背景、矿床特征、时空分布规律等进行了总结,综合前人的研究成果,峪耳崖金矿赋存于中元古界长城系高于庄组陆海相沉积地层,成矿岩体为中生代燕山期花岗岩。并与区域上金成矿条件进行对比分析,简述了成矿地层与岩体的关系,梳理了金矿床控矿因素、形成机制等问题,为今后进一步找矿勘查提供基础理论支撑。

冀东幔枝构造成矿作用及其地质找矿分析

简要回顾了从“变质核杂岩→盆山耦合→一盆多山→地幔热柱→地幔亚柱→幔枝构造”等研究过程,逐步完善成为幔枝构造成矿控矿理论体系。幔枝构造是地幔热柱多级演化的第三级单元,它不仅是陆内伸展构造的一种常见构造形式,也是重要的成矿控矿构造。深源含矿流体通过地幔热柱—地幔亚柱—幔枝构造—有利构造扩容带,迁移到幔枝构造的脆韧性—韧脆性主、次级拆离带,侵入岩体的内、外接触带,密集的构造裂隙带,多种脉岩与围岩的接触带等有利构造部位集聚成矿。在河北省建立了若干个幔枝构造,由于篇幅所限,仅解剖了冀东幔枝构造不同部位、不同成矿类型。核部是杂岩控矿—金厂峪金矿,侵入接触小岩体控矿—峪耳崖金矿,以及上盘盖层拆离带控矿—尖宝山金矿,探讨其核部岩浆-变质杂岩、外围拆离滑脱层以及上叠断陷盆地的成矿作用,确定找矿方向,总结成矿规律,归纳成矿模式,指导新一轮地质找矿。

热力构造的概念分类特征及其研究进展

热力作用是与应力、重力相类同的一类地质作用力。以往对其研究多有忽视,近年来研究进展较大。热力作用是盆地发育演化和改造的主要因素,随着大陆动力学研究的深化,大陆垂向热力作用及其热力构造陆续被发现。对目前尚无公认统一分类方案的热力构造,根据现今构造、地貌形态分为三类:正向穹窿型、负向塌陷型和边隆核陷型;按岩浆-热力作用影响深度等分为五种类型:(古)地热异常群集区、表浅层火山喷发-热液活动-浅成斑岩侵入型、热力背斜(热穹隆)型、中深层侵入型(含壳内热柱型)、地幔热柱型。深度分类的第二类表浅层火山喷发-热液活动-浅成斑岩侵入型又可再分为许多亚类:火山-热力管道、环状断裂、破火山口和火山塌陷、中浅成侵入型(含变质核杂岩和浅层热穹隆)、隐伏热力构造。热力背斜(热穹隆型)实际为中成或中浅成岩浆侵入型;中深层侵入型多在盆地基底或中下地壳内活动或造山带内产出,可称为地壳热异常柱,在地壳内分布规模不大,盆地下部一般难以直接见到,要依靠地球化学、地球物理等技术手段来确认;岩浆岩体侵入的深度不一,热力构造类型和发育程度不同;地幔(或地壳)热柱型影响深度最大,没有明显的地貌显示,要依靠深部构造岩石学、地球物理学等间接研究方法确认。地质-地球物理-地球化学综合研究应该是一种有效的研究方法。盆地深部多层结构研究发现热力构造区多具有明显的垂向极低电阻率值区和壳内低阻层,应为地壳热异常柱,有其特殊的热力作用环境。盆地深部热力作用与热力构造的复杂性和较强烈活动性,对盆地能源研究与评价及煤油气铀成矿成藏的勘探评价等方面均具有重要的影响意义。

华南地区中生代多金属矿床形成与地幔柱关系

华南地区中生代多金属矿床形成与地幔柱关系毛景文李红艳王登红彭聪（中国地质科学院矿床地质研究所，北京１０００３７）关键词多金属矿床地幔柱构造华南地区在华南地区，中生代有大量花岗质岩浆的侵位和成矿，形成了以柿竹园钨多金属矿床、大厂和个旧超大型锡多金属矿床...

华北地区两个世代深部构造的识别及其意义——燕山运动与深部过程

通过对华北地区地震层析成像成果的研究,将其深部构造划分为三带:1大型软流圈上涌柱带,主要出现两个大型软流圈上涌柱;2过渡带,呈现4个小型软流圈上涌柱(软块)与岩石圈较厚区(硬块)相间的构造格局;3巨厚岩石圈带,为巨厚岩石圈(鄂尔多斯硬块)稳定区。依据岩石圈热力学衰减原理,一定体积的深部构造可存留200～300Ma之久,而传导入浅表的热量则扩散较快。故以大地热流值为主,结合浅层岩浆活动可将本区中生代与新生代的软流圈上涌柱区分开来:渤海湾柱、大同柱和南阳柱属新生代,邯郸柱、中条柱和吕梁柱则属于中生代燕山期。在此基础上,建立了燕山期深部构造与浅表岩浆构造活动关系的模式:在强大的分散热力作用下,软流圈上涌柱柱头中大量热浮物质向上熔蚀薄的岩石圈及下地壳,混染而主要形成中酸性岩及有关矿产;而在软流圈上涌柱与岩石圈的陡接触处,由于该处热力集中,致使幔源物质底侵下地壳,并再熔融上侵形成偏碱性—碱性杂岩及相应矿产。

鲁西地区地质构造特征及其形成机制

根据区域地层(体)中部老外部新的环状分布,断裂构造的环状、放射状展布,核部缓倾拆离滑脱构造的发育特点,幔源岩浆活动以及区域岩石学、岩石化学、同位素地质学等方面的研究,探讨了鲁西幔枝构造特征及其形成机制。研究认为鲁西地区北西向陡倾韧性剪切带切割了深部华北地幔亚热柱向外拆离的地幔岩,导致其减压释荷形成深熔岩浆。岩浆演化序列表现出岩浆基性程度由高变低、侵入深度由深变浅、围岩蚀变由强变弱的总体演化趋势。由于强烈的岩浆上侵使得变质基底隆升、盖层拆离滑脱,形成典型的鲁西幔枝构造,在顶部则发育一系列明显的拆离掀斜断块。

华北东部地幔热柱的特征与演化

燕山运动以来,华北东部地区发生了翻天覆地之构造转变,构造体制从印支期末华北地块与扬子地块的拼贴-增生,转变为地幔热柱演化-区域伸展断陷。华北地幔热柱强烈上隆过程中,在岩石圈底部受阻并呈蘑菇状向外拆离流变,在使上部岩石圈发生热减薄-断陷的同时,向外拆离流变的地幔岩在盆地外围受到韧性剪切带的切割,导致深熔岩浆活动并带动围岩上隆,形成一系列次级隆起(幔枝构造)。地形地貌上亦从东部隆起的高原转变为一盆多山耦合格局——地幔热柱上部的热减薄断(拗)陷与外围的一系列幔枝构造的空间有机组合,即华北东部裂陷盆地西与太行造山带、北与燕山造山带、东与朝鲜半岛、南与大别造山带(即中心裂陷盆地与外围各幔枝构造)均为盆-山耦合关系。

冀东峪耳崖金矿成矿物质来源探讨

通过对峪耳崖金矿硫、铅、氢、氧、碳、稀有气体同位素、包裹体研究以及与区域对比分析,对金、银成矿物质来源进行探讨。认为峪耳崖矿区成矿物质应主要来自地核,受深部过程的约束,成矿物质随地幔热柱多级演化向地表迁移,在其上升过程中,与壳源物质发生部分混染,使所测同位素数据往往表现出以深源为主、并混有少量壳源物质的特征。