Magma Mixing and Mingling for Xiangjiananshan Granitic batholith at eastern area of the East Kunlun Orogenic Belt

The East Kunlun Orogenic Belt(EKOB)in northeast margin of the Qinghai-Tibetan Plateau is an important part of the Central Orogenic System(COS).During the long-time geological evolution,complicated tectono

Zircon U-Pb geochronology and Hf isotopic constraints on petrogenesis of Carnian Huanglonggou granodiorites in Wulonggou area of Eastern Kunlun Orogen,NW China

The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogenic gold-bearing fault.This study investigated the major and trace-element compositions,zircon U-Pb dates and zircon Hf isotopic compositions of the Huanglonggou granodiorite.One Huanglonggou granodiorite sample yielded a weighted mean U-Pb zircon age of^221 Ma(Carnian).The Carnian granodiorite is metaluminous,with high alkalis contents of 6.37%--8.86%,high Al_2O_3contents of 15.41%--16.19%,high Sr contents of(426--475)×10^(-6),relatively high Sr/Y ratios,high(La/Yb)_Nvalues and low HREE,suggesting an adakite type high-Si O_2granite.The Huanglonggou granodiorite sample has zirconε_(Hf)(t)values ranging from-4.4 to+1.1.These Hf isotopic data suggest that the Carnian granodiorite was likely derived from the partial melting of subducted Paleo-Tethys oceanic slab.It is suggested that the Late Triassic granodiorite was emplaced during the northward subduction of Paleo-Tethys oceanic slab.Orogenic gold mineralization in the Wulonggou area formed after the emplacement of the Late Triassic intrusive rocks.

Magma Mixing and Mingling for Xiangjiananshan Granitic batholith at eastern area of the East Kunlun Orogenic Belt

The Changning Menglian belt is an important area of research on the evolution of the Paleo Tethys ocean structure,the belt can be solved such as the Changning Menglianbeltposition;sequencestratigraphy;sedimentary environment;nature and its tectonic evolution history and tectonic domain and Gut Tis relationship;therefore,the research on Chang Ning Menglian zone have a great significance to solve many problems of the Sanjiang fold belt in Tethys and Himalaya tectonic area.'Hot spring'is located in the west margin of the southern Changning Menglian belt,studying Yunnan Fengqing hot spring group'geological and petrology characteristics roundly and in depth,concluding the metamorphism and deformation characteristics,clarifying the metamorphism effect and its stages,understanding the association its combination with the Changning Menglian belt between,therefore it has the great significance to solve the geological evolution history in the Sanjiang area,especially the paleo Tethyan tectonic belt,as well as Gondwana and Eurasia boundaries and other major problem.Through collect and read the literature data,measurement of field section,geological investigation,research and Study on rock sheet indoor,rock composition test,electron probe testing system,summarize the geological characteristics and petrological characteristics of'hot springs group',and through the discussion of the geochemical characteristics of rocks,explore its rock assemblages,characteristics of original rock and analysis of metamorphism and deformation stages,to provide basic data for regional geological evolution.The study shows that the main lithology is biotite quartz schist,mica schist and epimetamorphic sandstone interspersed with a small amount of phyllonite,granulite,silicalite,carbonaceous slate and phyllitic cataclasite that contains some pressure breccia.The metamorphic mineral paragenetic assemblage of the representative rock is:M1 biotite(Bi)+plagioclase(Pl)+quartz(Q),and M2 muscovite(Mus)+quartz(Q).The protolith is felsic rock and sedimentary rock that belongs to argiloid.On the basis of comparison,the stratigraphic sequence of the protolith is consistent with the type section of Wenquan formation.Along with the subduction(Hercynian)-subduction(Indosinian)-orogenic(Yanshan Himalayan period)process of Changning Menglian belt,hot springs group experienced two stages of metamorphism and three stages of deformation,metamorphic temperature at400-500℃,the pressure is foucs on 0.3-0.62Gpa,and shown the retrograde metamorphism of the low greenschist facies.Geological age of hot springs formation is early Devonian(survey team of Yunnan District three units,1980),sedimentary environment is mainly shallow and semi deep sea,observed Bouma sequence in rock slice,therefore,the depositional environment may be fan or basin of sea,the sedimentary formations are mainly clastic rocksiliceous rock formation,the upper coal—contained formation.With the Changning Meng Lian ocean expansion,ocean island begin to develop,material deposition continuing,appearing volcano material,the protolith may contain volcano matter through studying the thin section.To the Late Permian,Crust of Changning Menglian ocean begin to subduct to the east of the Yangtze block,ocean basin began to close,but it still has formation here at this time,mainly shallow carbonate formation,with proceeding of subduction,in the low temperature groove(7Km deep),due to changes in temperature and pressurer,appearing metamorphism(M1)and deformation(D1)for the first time,the shear effect produced by deformation lead to some cleavage,occurring regional foliation S1,major metamorphic minerals formed in metamorphism is long flake biotite.The main metamorphic mineral assemblages are biotite(Bi)+feldspar(Pl)+quartz(Q).Subsequently,crustal uplift,depositional break,because the Changning Meng Lianyang has closed during the Indosinian period,Baoshan-Zhenkang block in the west and the Yangtze block in the east knocked each other.In the Indosinian,under the action of faults,the hot spring formation clipping and retracing,back to a position about1-2Km depth,the position is still belongs to the low temperature groove,and occurring axial cleavage in the core of the fold,namely S2.That is,the emergence of the second metamorphism(M2)and deformation(D2).The deformation is affected by the strong pressure,so the rock have dewatered,so the second metamorphic deformation process is affected by temperature(T),pressure(Ps)and fluid(C).The main metamorphic minerals in the second generation of metamorphism is Muscovite,while there have some of biotite formed in same period,find that the first phase of biotite parallel growth of rock slice,namely S1 parallel S2,and we can see incomplete metamorphism biotite,so the the Muscovite is formed by the first stage of metamorphism and metamorphic biotite.The main mineral of the second stage metamorphism is Muscovite(Mus)+quartz(Q) Then,the crust continues to rise,the sedimentary break continues.In the Jurassic Cretaceous start orogeny,namely Yanshan period intracontinental orogeny,occurred third deformation(D3),under extrusion shearing,S3 emergencing,after Yanshan intracontinental orogenic period,in Himalayan period there have large-scale nappe structure and differential uplift and faulting.So the third deformation(D3)strengthened,with weak metamorphism,sericite emergencing.

Sulfur-and Lead-Isotope Geochemistry of the Balugou Cu-Pb-Zn Skarn Deposit in the Wulonggou Area in the Eastern Kunlun Orogen, NW China

The small-scale Balugou Cu-Pb-Zn skarn deposit（45 298 tonnages of ore at 0.1% to 3.99% Cu, 0.20% to 0.43% Pb and 0.76% to 10.92% Zn） is located in the Wulonggou area in the eastern Kunlun orogen, NW China. Ore deposition is spatially and temporally related with the pre-collisional Anisian Balugou granites（~244 Ma）. The mineralization hosted by the contact between marble beds within the Paleo-Proterozoic Jinshuikou Group and Balugou granites, was structurally and lithologically controlled. The mineralogy of the Balugou deposit includes an early simple skarn mineral gangue（epidote with little diopside） and a late complicated quartz sulfide assemblage（pyrite, pyrrhotite, chalcopyrite, sphalerite, galena, bornite, quartz, carbonate and chlorite）. The δ34S values of eighteen sulfides range from-2.1‰ to ＋2.8 ‰, with an average of ＋0.07‰, and the calculated δ34SH2S values for H2 S in hydrothermal fluids range from-3.2‰ to ＋2.4‰, with an average of ＋0.03‰, suggesting a relatively homogeneous magmatic（±mantle） source, with sulfur produced directly by the Balugou granites. The sixteen sulfides have 206Pb/204 Pb ratios from 18.367 4 to 18.384 1, 207Pb/204 Pb ratios from 15.634 6 to 15.641 5, and 208Pb/204 Pb ratios from 38.455 5 to 38.485 0, which are close to those of K-feldspars from the Balugou granites, but are far away from age-corrected lead isotopic ratios of six wall-rock samples. So it was considered that the Pb sources of sulfides must be almost derived from the Balugou granites rather than the older wall-rocks. Collectively, it＇s suggested that the Balugou Cu-Pb-Zn deposit belongs to skarn deposit, and the sulfur and lead deposited in it were leached from the Anisian Balugou granites.

Fission Track Thermochronology Evidence for Multiple Periods of Mineralization in the Wulonggou Gold Deposits, Eastern Kunlun Mountains, Qinghai Province

It is a puzzle to determine metallogenetic ages in the world. This article uses zircon fission track （FT） dating to probe the mineralizing epochs of Wulonggou （五龙沟） gold ore deposits in eastern Kunlun （昆仑） Mountains. Total of six zircon FT ages have been obtained and can be divided into groups of 235-216 and 197-181 Ma, as well as 162 and 124 Ma, revealing multiple epochs of metalloge- netic processes took place in Wulonggou area, mainly first two age groups. The mineralizing ages be- come lower from northeast Yanjingou （岩金沟） to southwest Hongqigon （红旗沟）. The second epoch of 197-181 Ma is first achieved by this work. It is shown that the FT ages consist with other isotopic data and reflect different regional thermotectonic events.

东昆仑东段浪木日地区地球化学异常信息提取方法研究及异常查证

青海沟里地区位于东昆仑造山带东段,根据水系沉积物地球化学测量已发现了多个矿床(点),具有较好的找矿潜力。本文选取沟里地区巴加别里赤尔幅(浪木日地区)1∶5万水系沉积物地球化学测量数据为研究对象,利用统计学方法和趋势面分析法两种方法进行异常信息提取。结果显示,趋势面分析法相较于传统统计法,圈定的异常面积更大、浓集中心更明确、分带特征更明显,且与已知矿床点的吻合度更高,整体上具有强化低背景异常的优势。同时利用趋势面分析法提取了3个元素组合,并对套合性和相关性突出,且与区内浪木日铜镍硫化物矿床相关的Cu-Zn-Cr-Co-Ni组合异常进行异常剖析。结合区内地质特征和浪木日矿区矿体分布情况,圈定了哲扎空龙洼东、龙里、瑙格木东和卡鲁南等找矿远景区,为区内下一步铜镍找矿工作提供了方向。

东昆仑茫崖河东地区地球化学钴异常与含矿地质体的响应

近年来,在东昆仑地区以地质找矿为目的开展的大比例尺1∶2.5万地球化学测量工作,具有快速、准确定位异常源的特征,在找矿勘查中被广泛应用,并取得了良好的找矿成果。通过开展1∶2.5万水系沉积物测量工作,在东昆仑茫崖河东地区圈出了以Cu、Co、Ni等元素组合为主的综合异常12处,其中以Co为主的综合异常有1处,各元素异常套合较好,相对规模大,异常强度高,具有明显的浓度分带。Co异常与奥陶系祁漫塔格群地层关系密切,区位一致性好。经异常查证,在GA16、GA26、GA11、GA39等异常内发现4条钴矿化带,带内圈定出了3条钴矿体及多条矿化体。综合分析认为该区具有优越的成矿地质条件、良好的地球化学特征,取得了较好的找矿效果,具备大中型钴矿的找矿潜力。

东昆仑香日德地区晚三叠世花岗岩LA-ICP-MS锆石U-Pb定年、岩石成因和构造意义

东昆仑地区广泛分布了大量花岗岩。已有的研究工作表明,东昆仑地区的花岗岩主要形成于晚二叠世-中三叠世和晚三叠世两个时期。本文提供了香日德地区二长花岗岩和花岗闪长岩的锆石U-Pb定年数据和全岩化学,稀土微量元素及Sr、Nd同位素地球化学研究资料,结合前人对该区不同时期花岗岩的研究成果,对香日德晚三叠世花岗岩的成因及其形成的动力学背景进行了讨论。研究表明东昆仑东段香日德地区的二长花岗岩和花岗闪长岩分别形成于223.2±1.7Ma和220.6±1.5Ma,属晚三叠世花岗岩浆作用的产物。根据该花岗岩的主量元素(特别是A/CNK比值),岩石富集大离子亲石元素(LILE:Rb、Th和K)和轻稀土(LREE),明显亏损高场强元素(HFSE:Nb、Ta、Ti和P),以及岩石具有相对高的Isr值(0.70820~0.71148)和相对低的εNd(t)值为-6.4^-3.6和较古老的模式年龄t2DM(1.5~1.7Ga)等地球化学特征,论证了该花岗岩的成因,指出香日德花岗闪长岩-二长花岗岩的起源和成因与碰撞后的背景下岩石圈的拆沉诱发的古老地壳物质的部分熔融作用有关,晚三叠世花岗岩岩浆作用是对自晚海西期以来幔源玄武质岩浆长期的底侵作用及地壳不断加厚的一种响应。它进一步证明在东昆仑地区,阿尼玛卿古特提斯洋的俯冲作用一直持续到早三叠纪,至晚三叠世才全面转入陆内碰撞造山阶段。晚三叠世花岗岩与晚二叠世-中三叠世花岗岩在暗色包体含量、岩浆混合作用的特征等方面的差异,可以用幔源物质贡献量的差异以及花岗质岩浆作用所经历的MASH过程的不同来解释。

东昆仑成矿带典型矿床分析

在综述东昆仑地区成矿地质背景及成矿条件的基础上,通过对肯德可克、驼路沟、督冷沟和大场等典型矿床的剖析,详细论述了矽卡岩型铁多金属矿、海相火山喷气沉积叠加后期改造型钴(金)矿、块状硫化物型铜钴矿和造山型金矿的成矿特征、成矿规律及找矿前景,并结合区域成矿模式、找矿模型和各类矿产、异常的空间分布特征确定出8个成矿远景区,13个找矿靶区。同时指出东昆仑各成矿带的成(找)矿潜力由大到小的依次排序为:昆南成矿带≈阿尼玛卿-北巴颜喀拉成矿带>昆北成矿带>>昆中成矿带。

新疆东昆仑于沟子地区与铁-稀有多金属成矿有关的碱性花岗岩地球化学、年代学及Hf同位素研究

东昆仑祁漫塔格地区是近年来发现的具有优越多金属成矿条件的地区,区内中-酸性侵入岩广泛发育且与成矿关系密切。于沟子铁-稀有多金属矿床位于祁漫塔格地区西部,矿床主要由产于钾长花岗岩外接触带矽卡岩内的铁-铜（钼）多金属矿化体及产于花岗岩体内部的铌、铷等稀有元素矿化体组成。锆石LA-MC-ICP-MS定年测得钾长花岗岩U-Pb年龄为210.0±0.6Ma,属晚三叠世末期岩浆活动的产物。岩体主要由条纹长石（60%~65%）、斜长石（10%~15%）、石英（20%~22%）、钠闪石（4%~5%）和少量黑云母（1%~2%）等组成,为典型的碱性花岗岩。地球化学特征上,该岩体具有高硅、高钾、准铝、钙碱性特点,富Nb、Zr、Rb、Th、U,贫Ba、Sr、P、Ti等元素,稀土元素总量较高,富集轻稀土,具强烈的负Eu异常（δEu=0.09~0.26）,属于A型花岗岩。锆石εHf（t）值为-6.71~2.25,平均为-1.15,二阶段Hf模式年龄（t DM2）为1102~1674Ma,显示在成岩过程中有地幔物质的参与。综合研究认为,于沟子岩体形成于晚三叠世末后造山板内伸展阶段,该碱性花岗岩的确定,标志着东昆仑祁漫塔格地区在晚三叠世末（212~210Ma）已逐步演化为伸展构造背景下的后造山构造阶段。同时矿床的成矿时代、氧同位素及电子探针结果均显示花岗岩与铁-稀有多金属成矿有关,指示出该类型碱性花岗岩具有良好的铁-稀有多金属成矿潜力。

青海西部祁漫塔格地区矽卡岩型铁铜多金属矿床的矽卡岩类型和矿物学特征

青海西部祁漫塔格地区矽卡岩型铁铜多金属矿床分布广泛,主要发育两类矽卡岩,即钙矽卡岩和锰质矽卡岩,少数矿区还有镁矽卡岩。钙矽卡岩的组成矿物主要有透辉石、钙铁辉石、钙铝-钙铁系列石榴石、绿帘石、阳起石和方柱石,常伴随Fe、Cu、Mo矿化,构成钙矽卡岩型铁多金属矿床或铜(钼)矿床,而锰质矽卡岩主要由锰钙铁辉石组成,含少量锰三斜辉石,常伴随Pb、Zn(Ag)矿化,构成锰质矽卡岩型铅锌(银)矿床;镁矽卡岩主要组成矿物有透辉石、镁橄榄石、钙镁橄榄石和金云母,仅伴随磁铁矿化。因此,矽卡岩类型是判别矿化类型的重要标志之一。

东昆仑早古生代花岗岩锆石U-Pb年龄及其地质意义

应用激光烧蚀多接收器电感耦合等离子体质谱(LA-MC-ICPMS)方法,对东昆仑五龙沟地区花岗岩样品进行了锆石U-Pb定年研究。结果表明,黄龙沟中部的糜棱岩化二长花岗岩(B20-14)中岩浆锆石206Pb/238U年龄平均值为(417.7±2.0)Ma,黄龙沟上部的糜棱岩化二长花岗岩(B21-2)中岩浆锆石206Pb/238U年龄平均值为(419.7±2.3)Ma,深水潭粗中粒二长花岗岩(B20-8)中岩浆锆石206Pb/238U年龄平均值为(419.9±2.0)Ma,红旗沟中部的粗中粒二长花岗岩(B25-9)岩浆锆石206Pb/238U年龄平均值为(419.0±2.0)Ma。它们代表了五龙沟地区所研究花岗岩的形成年龄,其形成时代均为晚志留世,记录了东昆仑早古生代的岩浆活动。本文获得的东昆仑五龙沟地区的晚志留世花岗岩可能与东昆仑早古生代洋盆闭合后的碰撞造山作用有关。花岗岩中1861Ma、1666Ma古元古代继承锆石的发现,表明东昆仑造山带的基底物质为古元古代。

东昆仑水闸东沟-黄龙沟金矿床硫化物矿物学特征对可见金形成条件的制约

东昆仑五龙沟地区水闸东沟-黄龙沟金矿床处于昆中断裂北部,受NW向构造控制,矿区出露中元古界小庙组和新元古界丘吉东沟组地层,岩浆岩以早古生代和早中生代侵入岩为主。围岩蚀变以绢云母化和硅化为主,矿体严格受NW向剪切带控制,赋矿岩石为早古生代正长花岗岩和新元古代丘吉东沟组板岩。综合野外地质特征、矿相学观察和电子探针测试结果,水闸东沟-黄龙沟金矿床可划分出4个成矿期:沉积期、热液Ⅰ期、热液Ⅱ期和表生期。新元古代沉积期属金的初步富集期;早古生代热液Ⅰ期可分为4个阶段,其中第一阶段(磁黄铁矿-毒砂-斜方砷铁矿-自然金阶段)是金的主成矿阶段;早中生代热液Ⅱ期金再次活化富集;表生期代表矿体暴露地表后的变化。热液Ⅰ期的磁黄铁矿-毒砂-斜方砷铁矿-自然金阶段,由早至晚体系温度和硫逸度升高,代表前进变质作用,变质条件达绿片岩相上限。斜方砷铁矿交代毒砂的结构中通常可以观察到可见金,说明该阶段是由不可见金向可见金转化的重要时期,可见金形成于绿片岩相上限的温度范围内。

东昆仑祁漫塔格地区花岗岩类时空变化的构造控制——来自钾钠含量变化的证据

系统收集东昆仑祁漫塔格地区花岗岩类岩石化学数据,统一采用Collins,etal.(1982)提出的K2O-Na2O分类图解法,获得各个地史时期花岗岩的成因类型。结果表明,晋宁期以S型为主,优势方位不明显。加里东期优势方位为北东向,以A型为主,北西向处于次要地位,以I型为主。海西-印支期,优势方位为北西向,岩石类型在海西早、中期以I型为主,海西晚期至印支期以A型为主。此时北东向处于次要地位,岩石类型以A型为主。燕山期,整个祁漫塔格地区昆中断裂以北均为A型,以南形成新的构造岩浆岩带,岩石类型主要为I型。并且,燕山期昆中断裂以北早期以北西向为主,晚期以北东向为主。上述情况说明,至少自加里东期以来,该区花岗岩的空间展布、发育规模、成因类型等诸方面都始终受到北东向和北西向两组构造带的活动强度、力学性质交替变化的控制,并且由老到新总体上存在着由北向南逐渐迁移的变化趋势。因此,祁漫塔格岩浆岩带并非同一构造机制下形成的岩浆弧,而是由北东向和北西向两组构造岩浆活动带交替作用控制的、成因类型不同的花岗岩类共同组成的复合构造岩浆岩带。

东昆仑沟里地区暗色包体及其寄主岩石地球化学特征及成因

通过青海东昆仑东部沟里地区阿斯哈岩体中寄主闪长岩和暗色微粒包体的岩相学、全岩地球化学研究，确定了岩石成因及其构造属性。阿斯哈岩体中暗色包体广泛分布，包体岩性主要为角闪辉长岩。包体具有岩浆结构，部分包体具有塑性流变特征，包体中可见寄主岩石矿物的捕掳晶和针状磷灰石，表现出岩浆混合的岩相学特征。主岩及暗色包体同属准铝质、高钾钙碱性钾玄岩系列过渡岩石，主量元素在Harker图解及 Al2 O3/K2 O CaO/K2 O和 SiO2/CaO K2 O/CaO的共分母协变图上具良好的线性关系，反映两者成分的变化与岩浆混合作用有关。两者的稀土元素配分模式总体一致，显示二者密切的成因联系。两者都富含大离子亲石元素（Rb、K ），相对亏损高场强元素（Nb、Ta、P、Ti ）。暗色包体具有贫硅（w（SiO2）＝50．70％～53．88％）和富镁、铁、钙的地球化学特征，其 Mg＃值较高（Mg＃＝0．52～0．59），暗示其来源于俯冲带流体交代地幔楔的部分熔融。主岩的 Rb/Sr值为0．22～0．27，接近地壳平均值，Nb/Ta值为14．5～15．2，介于地幔平均值与地壳平均值之间，表明寄主岩石岩浆具有壳源岩浆的性质并经历了幔源岩浆的混合作用。结合区域构造演化及构造判别，认为阿斯哈岩体形成于安第斯型活动大陆边缘的构造环境。早三叠世，阿尼玛卿洋向北俯冲，俯冲带流体交代地幔楔，导致其部分熔融形成基性岩浆，底侵的幔源基性岩浆诱发下地壳部分熔融并与之发生混合形成本区闪长岩，而其中的暗色包体为幔源岩浆混合不彻底的产物。

东昆仑清水泉辉绿岩脉地球化学及LA-ICP-MS锆石U-Pb定年

结合地质、地球化学及LA-ICP-MS锆石U-Pb定年研究表明,东昆仑清水泉地区辉绿岩脉的主元素以低TiO_2(0.68%～1.24%)和较低的MgO(4.96%～7.25%)及K_2O(0.51%～1.03%),贫P_2O_5(0.09%～0.16%),Na_2O>K_2O为特征,∑REE总量较高,LREE明显富集。与原始地幔相比,明显富集Rb、Ba、Th、U和Sr,高场强元素分异明显,出现Nb、Ta亏损和Th富集特征,结合Nb/La、Hf/Ta、La/Ta、Ti/Y、Zr/Y和Th/Nb等比值综合分析认为岩浆来源于富集地幔,源区曾受不同程度的俯冲带流体交代作用的影响,应形成于活动大陆边缘环境;岩脉的LA-ICP-MS锆石U-Pb定年结果为436.4±1.2Ma(MSWD=0.37),代表清水泉辉绿岩脉的结晶年龄,为早古生代晚期东昆仑洋消减俯冲的弧后拉张裂解的形成时限提供了约束。

东昆仑小庙基性岩脉地球化学及LA-ICP-MS锆石U-Pb定年

东昆仑小庙辉绿岩脉侵位于前寒武纪金水口群变质基底中,岩石地球化学研究表明:它是以低TiO2和较低的MgO,Nb、Ta亏损和Th富集为特征,贫P2O5,Na2O>K2O,富集大离子亲石元素Rb、Ba、Th、U、Sr和LREE,高场强元素分异明显,地壳源区对辉绿岩的影响很大,形成于大陆拉张带或裂谷初期环境。LA-ICP-MS锆石U-Pb同位素定年结果表明:1996～2428Ma年龄可能代表岩浆捕获锆石年龄,形成于太古宙至古元古代的区域性构造热事件;3个较一致点的加权平均年龄(733.6±6.6)Ma(MSWD=0.038)为辉绿岩结晶年龄,可能代表了新元古代东昆仑地区裂解的时间,这与Rodinia超大陆裂解相对应。

东昆仑五龙沟地区糜棱岩化花岗岩年代学、岩石成因及其构造意义

位于东昆仑中段五龙沟地区深水潭矿段糜棱岩化钾长花岗岩LA-ICP-MS锆石U-Pb年龄为(390±3.9)Ma。该岩体具有较高的SiO_2(74.86%~76.64%)、K_2O(5.20%~6.06%)和全碱含量(K_2O+Na_2O=8.05%~8.83%),呈现明显的Ba、Nb-Ta、Sr、P和Ti的负异常,以及强烈的Eu负异常(δEu=0.07~0.12),显示A型花岗岩特征。结合区域上志留纪—泥盆纪岩浆岩的研究,认为东昆仑造山带早泥盆世已进入后碰撞伸展阶段,早中泥盆世之交为伸展最强烈时期,形成了颇具规模的在A型花岗岩,也代表加里东造山旋回的结束。

东昆仑祁漫塔格地区构造岩浆作用与成矿关系初步探讨

以钾、钠含量变化为主要指标获取祁漫塔格地区各个地史时期花岗岩类的成因类型,结果表明,区内构造岩浆作用在时间上具有明显的阶段性,加里东中晚期是本区第一次侵入岩浆作用的高峰期,印支中晚期为本区花岗岩浆作用的鼎盛时期,加里东中晚期和印支中晚期也是区内两次区域成矿作用的大爆发期。岩体分布具有明显的方向性,主要由北东向和北西向两组构造岩浆岩带组成,而且,至少自加里东期以来,两组岩带的空间展布、发育规模、成因类型等诸方面都具有长期此消彼长的变化特点。同时期,两组构造带的碱交代作用类型、成矿作用特点都存在明显的区别,加里东中晚期北东向构造带以钾质交代作用为主,形成了白干湖大型钨锡矿;此时北西向构造带则以钠质交代作用为主,形成以驼路沟钴矿为代表的钴矿系列。此外,同一岩带,花岗岩成因类型不同,其成矿作用特点有别。

东昆仑五龙沟金矿田控矿构造带的变形条件——来自EBSD组构的启示

五龙沟金矿田是东昆仑地区最重要的金矿集中区之一,金矿田主要控矿构造为偏脆性断裂破碎带,在三条控矿构造带中仅在萤石沟—红旗沟构造带邻近北侧的局部出露韧性变形带。本文作者运用电子背散射衍射技术(EBSD)技术方法,对东昆仑五龙沟金矿田萤石沟—红旗沟构造带变形岩石的组构分析显示,花岗质糜棱岩韧性变形强烈,大部分样品石英变形机制是以中温I级柱面(1010)<1120>滑移为主,变形式样比较单一;少量样品为中高温II级柱面(101—0)<0001>滑移和中低温底面(0001)<112—0>滑移。从岩石组构特点结合宏观构造分析,五龙沟金矿田萤石沟—红旗沟构造带及其邻近北侧经历了中-中深层次、中-中高温条件(15~25 km,t=350~550°C,P=0.40~0.60 Gpa)的韧性变形,局部叠加中浅层次、中低温条件(10~15 km,t=250~350°C,P=0.25~0.40 Gpa)的韧脆性变形;而岩金沟和三道梁—苦水泉构造带为低温低压条件的脆性破碎带。结合变形花岗闪长岩年代学资料,确定构造变形时代为早中生代。