汉诺坝地区下地壳与壳-幔过渡带岩石波速实验研究

通过对汉诺坝新生代玄武岩中镁铁质麻粒岩相斜长辉石岩、榴辉岩相石榴辉石岩和辉石岩捕虏体,以及普通的太古代地体麻粒岩,进行高温高压下的波速测定和研究表明:高V p (7.0～8.0km/s)镁铁质捕虏体揭示现今下地壳和壳-幔过渡带组成特征,为幔源岩浆底侵导致地壳垂向增生和壳-幔过渡带形成提供了新证据;低V p (<7.0km/s)太古代地体麻粒岩,乃早期下地壳或上部下地壳的特点.     

辽西建平变质杂岩中花岗岩类岩石的锆石蒸发年龄及其地质意义

建平变质杂岩是辽宁西都太古代最下部地质单元,是华北地台北缘麻粒岩相带的重要组成部分。它由少量连续性很差的表壳岩及大量的ＴＴＧ岩石和其他深成侵入体组成。采用单颗粒锆石Ｐｂ蒸发法对其中的ＴＴＧ岩石及其他侵入岩进行了年龄测定。结果表明：本区ＴＴＧ花岗质岩浆约于２５２１Ｍａ开始活动,并于２５００Ｍａ左右达到高峰,形成了大量的ＴＴＧ质侵入体（包括部分喷出岩）;紧随其后,本区发生强烈的高级变质变形事件,此事件约于２４８３～２４９０Ｍａ达到高峰,使得已形成的岩石变成麻粒岩、紫苏花岗岩及斜长紫苏花岗岩等;于２４７２Ｍａ就位的与退变质作用有关的后构造花岗岩标志着本区高级变质变形事件的结束。据此,可以推测建平变质杂岩可能形成于陆块形成后不久即发生大陆碰撞和地壳加厚的晚太古活动大陆边缘的环境中。     

鲁东胶北地区的变形与变质演化史

本文依据在烟台－蓬莱－栖霞地区的详细构造与变质研究，分析胶北地区太古代以来的变形与变质演化历史及其意义．继太古代胶东群形成之后的胶东事件，在胶东群中造成了第一期的南北向构造和同构造麻粒岩相高级区域变质．于粉子山群沉积之后、大致１７亿年前发生的粉子山事件使胶北地区基底最后固结．这期造山事件在基底中产生了广泛的平缓变形面理、褶皱及同构造角闪岩相区域变质．晚石炭世的蓬莱事件，以北北东一南南西向挤压造成了蓬莱群及基底中普遍的北西西－南东东向褶皱及低绿片岩相区域变质．蓬莱事件是华北与扬子板块沿胶南带碰撞的结果．胶北地区的后蓬莱事件造成了局部的北北京向膝折和褶皱，并未伴生区域变质．这一变形事件可能是晚三叠世印支运动或侏罗纪燕山运动的结果．     

甘肃金川变质磁铁矿特征研究

在甘肃金川铜镍硫化物矿床周围实施JCSD钻探项目的过程中,发现磁铁矿化层.经过分析研究该磁铁矿化层的物质组分,时空分布及矿床成因等地质问题.表明金川龙首山铁矿含矿岩石及围岩主要为强烈变质的龙首山岩群晚元古界白家咀子组地层.磁铁矿化主要出现在斜长角闪岩和混合岩中.磁铁矿所赋存的斜长角闪岩经原岩恢复为沉积岩和火山岩两大类.表明铁元素的来源与陆源、火山沉积作用密切相关.进而说明磁铁矿属沉积变质型,区内的成岩作用即为成矿作用.磁铁矿的形成经历了陆源、火山沉积、区域变质改造和混合岩化改造等复杂的过程.     

辽西建平变质杂岩中花岗岩类岩石的锆石蒸发年龄及其？…

建平变岩杂岩是辽宁西部太古代最下部地质单元,是华北地台北缘麻粒岩相带的重要组成部分它由少量连续性很差的表壳岩及大量的ＴＴＧ岩石和其他深成侵入体组成。采用单颗粒锆石Ｐｂ函数法对其中的ＴＴＧ岩石及其他侵入岩进行了年龄测定。结果表明：本区ＴＴＧ花岗质夺浆约２５２１Ｍａ开始活动,并于２５００Ｍａ左右达到高峰,形成了大量的ＴＴＧ质侵入体（包括部分喷出岩）;紧随其后,本区发生强烈的高级变质变形事件,此事件约于     

内蒙古固阳地区新太古代侵入岩特征

内蒙古固阳地区分布着广泛的新太古代变质侵入岩,总体呈东西向带状,展布方向与区域构造线方向一致。岩石类型为斜长角闪岩、闪长岩、石英闪长岩、英云闪长岩,岩石总体为钙碱性系列,属于太古代TTG岩系的一部分;稀土配分曲线与高铝型TTG岩石的演化趋势相一致。在片麻状石英闪长岩中取2组锆石U-Pb年龄,获得2575～2676Ma锆石U-Pb等时线年龄,属新太古代末期。     

独山玉岩石学特征分析

独山玉矿区内岩石类型主要为次闪石化辉长岩、角闪岩及橄榄质科马提岩,岩石普遍呈碎裂、糜棱结构,总体属于铁质基性岩类.岩石蚀变普遍,特别是次闪石化遍及整个岩体.岩石是有明显的动力变质作用,显示出独山的个性格局.独山玉脉与次闪石化、钠黝帘石化和构造糜棱岩化关系密切.根据独山隐赋边界,推测整个基性岩区是玉石的成矿远景区.     

秦岭沙沟韧性剪切带长英质糜棱岩的变形变质作用

对秦岭沙沟韧性剪切带的主要岩石类型长英质糜棱岩的组构和变质矿物组合研究表明，其至少经历了３期构造事件，主变形期发生在角闪岩相条件下，温度约５３０℃；持续的岩浆分融／侵入和剪切作用是形成该糜棱岩的重要机制。     

秦岭沙沟韬性剪切带长英质糜棱岩的变形变质作用

对秦岭沙沟韧性剪切带的主要岩石类型长英质糜棱岩的组构和变质矿物组合研究表明，甚至少经历了３其构造事件，主变形其发生在角闪岩相条件下，温度约５３０℃；持续的岩浆分融／侵入和剪切作用是形成该糜棱岩的重要机制。     

松树沟超镁铁质岩体接触变质带中的矿物学

松树沟橄榄岩是一个弱蛇纹石化的超镁铁质岩体,它侵入在区域变质的斜长角闪片岩中。业已证明,该岩体有一个出露良好且未受破坏的高温变质带。可用以下证据来鉴定松树沟接触变质围岩:从远离接触带到靠近接触带斜长石成分愈来愈基性,由An_(12)—An_(60),角闪石的颜色从蓝绿—绿—褐绿—深褐色,辉石和柘榴石只局限于接触带的内部,向着接触带榍石减少,钛磁铁矿增多,穿过接触带,角闪石的化学成分表现出(Na K),Al和Ti的增多。     

煤田火区烧变岩成岩机理与利用

烧变岩是一种在以煤田火区为主要环境背景的复杂条件下,受燃烧变质作用和气液变质作用等影响产生的变质岩类。目前研究多聚焦于死火区岩层的岩石性质及水文地质意义,而缺乏对活火区烧变岩利用体系的研究。为了促进对烧变岩的研究,以砂岩为例分析了烧变岩的矿物成分与呈色,总结了以烧变岩为媒介探测火区的方法及其局限性,最后讨论了烧变岩层的热能回收及资源化利用。结果表明:在活火区新生的烧变岩其矿物成分随温度变化明显,而颜色随温度上升主要由铁、锰氧化物控制;根据矿物特性及热特征,烧变岩可以作为对煤火的探测依据,但探测方法均存在缺陷;热特征也体现了烧变岩蕴含一定体量的热能,可进行回收利用,而冷却后的烧变岩也具有丰富的用途。     

铜陵地区石炭系铁铜矿床的矿石组构组分特征

通过对铜陵地区主要铁铜矿床矿石组构研究表明，石炭系铁铜矿床中存在沉积成岩、热变质及热液充填、交代的矿石组构．结合矿石组分研究认为，铁、硫可能主要与石炭系有关，而铜质在原始沉积时较少，经后生变质改造，尤其是含矿热液的叠加再富集而成矿．该区存在两个系列，即沉积成岩－热变质系列（简称变质型）和热液充填交代系列（简称交代型）矿石，两个系列之矿物演化序列迥然不同，化学成分亦有明显差异。故认为铜陵地区石炭系铁铜（主）矿床属沉积成岩－（岩浆）热液叠加改造型矿床。     

新疆北山地区金矿床控矿因素与找矿标志

北山地区位于新疆东部塔里木地块东北缘，东西长约３００ｋｍ，南北宽约１００ｋｍ，近来发现了一系列金矿点。该区主要由古生界的沉积－火山岩系组成，局部含太古界至下元古界的结晶基底，覆中新生界盖层。两期重要的玄武质岩浆活动与金矿化有关。金矿点产于前寒武纪的准绿片岩中，但主要产于石炭纪的硅化和黄铁矿化岩石中，由走向ＮＥＥ－ＳＷＷ向的大型逆断层控制。金矿源来自上地幔部分熔融产生的玄武岩，后期经活化富集于北山地区南部推覆前缘叠瓦断层带中。矿物的晶形、成分、物性可作为良好的找矿标志。研究表明，北山地区有可能找到大型或超大型金矿床。     

太行山北段晚太古宙变质杂岩伸展变形带的初步研究

太行山北段太古宙的变质岩系自下而上分为阜平片麻杂岩、南营片麻岩和湾子层状岩系。阜平片麻杂岩和湾子层状岩系之间发育一条大规模低角度伸展变形带,沿该变形带南营片麻岩侵位。主变形带内部岩石发生强烈片理化,发育A型褶皱、鞘褶皱和眼球状岩块构造等韧性变形构造。其中矿物拉伸线理近 EW 向,剪切标志指示上盘(湾子岩系)向西,下盘(阜平片麻杂岩)向东的运动学特征。下盘发育平行于主变形带的小型韧性剪切带,上盘发育一系列铲形脆韧性断裂系。上、下两盘的PTt轨迹均为顺时针型,显示了地壳由褶皱增厚到拉伸减薄的隆升演化过程。     

Ca. 2.5 Ga TTG rocks in the western Alxa Block and their implications

The Alxa Block is considered part of the North China Craton, but the unambiguous Archean basement has not been reported. In this study, we present the first evidence of the Neoarchean rocks in the Beidashan area of the western Alxa Block. The petrographic and geochemical data show that these rocks are granodiorite with TTG (tonalite-trondhjemite-granodiorite) characteristics. Zircon U-Pb dating gave an age of 2522±30 Ma for the magmatic core and 2496±11 Ma for the metamorphic recrystallized rim. The near-identical age between the Latest Neoarchean magmatism and the high-grade metamorphism shows that these features were related to the same Latest Neoarchean-Earliest Paleoproterozoic tectonothermal event. The age-corrected Hf (t) value is mainly between 0.4 and 4.9. The two-stage zircon Hf model age ranges from 2.7 to 3.0 Ga, suggesting that the Mesoarchean- Neoarchean (2.7-3.0 Ga) juvenile crust was reworked at the end of the Neoarchean in the western Alxa Block. These data suggest that the western Alxa Block experienced a Mesoarchean-Neoarchean crust growth and Latest Neoarchean-Earliest Paleoproterozoic tectonothermal event similar to the North China Craton.     

Evidence of Nd isotope for unhomogeneity and origin of upper mantle of North China platform

Based on isptopic age of Sm-Nd and its initial composition and its evolution obtained during the recent years of archean metamorphic magnesio-ferro the vocanics of upper mantle of the North China platform, it is concluded that the isotopic composition of Archean upper mantle of the North China platform is not homogeneous, and values of I_ND don not change regularly through the whole Archean; in contrast, they present obvious differences in different regions. All this demands that the unhomogeneity of Archean upper mantle of the North China platform inherits initial unhomogeneity of origin, and the origin of the North China platform should contribute to uneven accumulation of planetesimals.     

Genesis of zircon and its constraints on interpretation of U-Pb age

Zircon U-Pb dating is the most commonly used method for isotopic geochronology. However, it has been a difficult issue when relating zircon U-Pb ages to metamorphic conditions in complex metamorphic rocks. Much progress has been made in the past decade with respect to the genesis of zircon and its constraints on interpretation of U-Pb age. Three methods have been proposed to link zircon U-Pb age to metamorphic conditions: ( i ) internal structure; ( ii ) trace element feature; (iii) mineral inclusion composition. Magmatic zircon shows typical oscillatory zoning and/or sector zoning, whereas metamorphic zircon has internal structures such as no zoned, weakly zoned, cloudy zoned, sector zoned, planar zoned, and patched zoned ones. Zircons formed in different geological environments generally have characteristic internal structures. Magmatic zircons from different rock types have variable trace element abundances, with a general trend of increasing trace element abundances in zircons from ultramafic through mafic to granitic rocks. Zircons formed under different metamorphic conditions have different trace element characteristics that can be used to relate their formation to metamorphic conditions. It is an effective way to relate zircon growth to certain P-T conditions by studying the trace element partitioning between coexisting metamorphic zircon and garnet in high-grade metamorphic rocks containing both zircon and garnet. Primary mineral inclusions in zircon can also provide unambiguous constraints on its formation conditions. Therefore, interpretation of zircon U-Pb ages can be constrained by its internal structure, trace element composition, mineral inclusion and so on.     

海拉尔盆地布达特群流体包裹体特征及来源

海拉尔盆地布达特群热流体活动频繁,脉体发育。脉体中发育3种不同类型烃类包裹体,即旱期富CH₄气态烃类包裹体、中期液态烃类包裹体、晚期气液两相烃类包裹体。通过对3种烃类包裹体宿卞矿物特征、均一温度测定、宿主矿物化学成分的分析,指出铁白云石脉的形成与岩浆成因及低温热液作用有关,石英脉的形成可能来源于深部流体。早期石英脉中富CH₄气态烃类包裹体可能同样来自于深部;中期铁白云石脉中液态烃类包裹体是热事件作用中高温变质水分解并携带了围岩中烃类物质进入裂缝中沉淀而成的;晚期石英脉、铁白云石脉中气液两相烃类包裹体则代表了布达特群油气成藏时油气运移、聚集的结果。结合沉积理藏史和热演化史恢复,认为布达特群成藏时间为60- 105 Ma,即伊敏组沉积初期开始,一直延续到青元岗组。     

Subduction age of Neo-Tethys oceanic crust in southwest Yunnan, China: Laser micro-area40Ar-39Ar dating

The basic granulite, which is considered to be the MORE based on geochemistry and isotopic characteristics[1], has been discovered recently as the enclaves in the Yingjiang island-arc magmatic suite on the border of Burma and west Yunnan, east of Myitkyina suture in the eastern Burma. The laser micro-area 40Ar-39Ar technique is used to date the age of garnet and cliopyroxene that is the result of the early metamorphic event. The isochron outcome is -74.4 Ma which is induced to be the age of the suduction event of the Myitkyina oceanic crust on the basis of the Cenozoic lithosphere tectonic evolution, tectonic thermal events and the age of deformation and metamorphism. The discovery of the high-grade or high-pressure metamophic rocks in the island-arc magmatic suite by the way of studying its P-T-t paths can provide a good way to study the age and process of oceanic crust subduction, slab break-off, metamorphic terrain exhumation and the evolution of paleoocean basin.     

Confirmation of ultrahigh-temperature metapelitic granulite in the Altay orogen and its geological significance

Through petrography, mineral compositions and P-T estimate results, an ultrahigh-temperature(UHT) metapelitic granulite has recently been identified from near Kalasu in the east of Altay city, with an assemblage gt-opx-silcd-sp-bt-pl-qtz. The orthopyroxene has a high-Al feature, and its Al2O3 content is as high as 8.7 wt%, indicating a UHT metamorphic condition. Its peak metamorphic condition is estimated as: P = *0.80 GPa, T = *960 °C. Metamorphic textural relations and P-T estimate results show a post-peak near-isobaric cooling anticlockwise P-T path. Zircon U-Pb age results(271 ± 5 Ma) support that the UHT metamorphic event in the region occurred in the Permian. The identification of the UHT metapelitic granulite from near Kalasu confirms the existence of the Permian UHT metamorphism in the Altay orogen, implying that the Permian extensional tectonic setting of a high-heat flow in the southern part of the Altay orogen may be closely associated with the Permian Tarim mantle plume activity.