内蒙古柴胡栏子金矿区闪长玢岩锆石U-Pb定年及其地质意义

内蒙古柴胡栏子金矿区断裂构造发育,岩浆岩类型复杂.本文在野外地质工作的基础上,通过锆石LA-ICP-MS U-Pb同位素年代学研究,得到了矿区岩浆岩的形成时代,并对海西期的岩浆活动进行了讨论.闪长玢岩样品中存在(2447±13)Ma(MSWD=0.0108)的继承性岩浆锆石和(296.6±3.5)Ma(MSWD=0.5...     

即墨地区莱阳群底部止凤庄组地质特征及其碎屑锆石LA-ICP-MS U-Pb年龄地质意义

为了了解盆地沉积初期的物源特征,对位于胶莱盆地东缘即墨地区早白垩世莱阳群止凤庄组沉积特征、物质组成及碎屑锆石进行了U-Pb同位素测年研究。野外调查表明,止凤庄组为一套陆源碎屑沉积,具有近源沉积的特点。南泊一带止凤庄组底部碎屑岩碎屑锆石LA-ICP-MS U-Pb年龄介于233~734 Ma,年龄分布于5个区间,呈现明显的幕式特征,至少记录了2次重要的构造热事件。侵入于止凤庄组石英二长岩的锆石U-Pb加权平均年龄为(123.50±0.95)Ma,限定了止凤庄组地层沉积上限年龄为123.50 Ma。综合分析认为,止凤庄组物源主要来自苏鲁造山带,部分来自扬子板块。这有助于了解胶莱盆地沉积初期其物源区苏鲁造山带的地体情况。     

突泉盆地突D2井林西组碎屑岩LA-ICP-MS锆石U-Pb年龄及地质意义

内蒙古突泉盆地南部突D2井钻遇厚层的暗色泥岩,发现具有晚二叠世特征的孢粉化石。为获取精确的地层同位素年龄,对500.0m井段发育的粉砂岩进行碎屑锆石LA-ICP-MS U-Pb同位素测试分析,得到100颗锆石的谐和—近谐和年龄。结果表明:碎屑锆石按年龄和频率分布特征可以分为5组:245.0～279.0 Ma(12颗,占12%),峰值年龄为263.0 Ma;282.0～346.0Ma(48颗,占48%);355.0～531.0Ma(21颗,占21%);615.0～993.0Ma(6颗,占6%);1.022～2.163Ga(13颗,占13%,207Pb/206Pb年龄)。最小年龄段年龄的加权平均为(261.7±6.2)Ma(MSWD=0.93,12颗),与最小峰值263.0 Ma的年龄吻合,测年样品沉积时间下限为263.0 Ma,沉积时代为晚二叠世,证实突泉盆地存在林西组暗色泥岩,以及大地电磁测深剖面上存在的第二套广泛连续发育的低阻层为林西组。沉积物源具有多样性和复杂性,主体来自东北各地块,同时存在华北板块和西伯利亚板块的物源信息((1.658±0.023)、(1.877±0.016)、(1.891±0.041)、(2.163±0.011)Ga)。林西组沉积时期,华北板块与西伯利亚板块开始俯冲碰撞过程,最终闭合时间在晚二叠世之后。     

湖南白马山岩体锆石SHRIMP U-Pb年龄及其地质意义

本文对湖南白马山印支晚期花岗岩体进行锆石SHRIMP U-Pb定年,结果表明：白马山复式岩体中黑云母花岗闪长岩谐和年龄值分别为224.1±2.3Ma和219.6±2.6Ma,属印支中晚期;而黑云母二长花岗岩得出213.8±2.5Ma的谐和年龄,属印支晚期。结合其他相关年代学数据,湖南白马山印支晚期花岗质岩浆经历了两期侵入活动,第一次侵入在220Ma左右,且分布广泛、规模较大,在后期约208Ma再次发生了一次岩浆活动。这也印证了华南印支晚期花岗岩存在两次明显的岩浆活动,同时对整个华南地区印支期花岗岩成因及演化特征具有重要意义。     

北京密云地区沙厂组条带状磁铁石英岩SHRIMP锆石U-Pb年龄及其地质意义

通过对北京密云地区沙厂铁矿条带状磁铁石英岩进行SHRIMP锆石U-Pb定年研究,主要获得两组锆石U-Pb年龄,分别为(1 806±13)、(2 464±18)Ma。结合其岩相学、阴极发光图像分析,这些锆石为变质成因锆石,因此,这两组年龄应代表条带状磁铁石英岩的两期变质作用时代,这与前人认为的华北克拉通东部陆块前寒武纪两期变质事件时间(约2.44Ga和约1.82Ga)相吻合。另外,在条带状磁铁石英岩中还发现了一颗年龄为(2 517±12)Ma的浑圆状锆石,代表了该磁铁石英岩中碎屑锆石的年龄,从而间接限定了该区条带状铁建造的形成时代为(2 464±18)~(2 517±12)Ma。结合前人研究资料,其可能形成于新太古代晚期。这些成果为该区乃至整个华北地区前寒武纪BIF型铁矿以及晚太古代至古元古代的构造演化提供了进一步详实的年代学资料。     

西秦岭多哇地区萨日加岩体LA-ICP-MS锆石U-Pb年龄、地球化学特征及其地质意义

西秦岭造山带发育大量的印支期高钾钙碱性花岗岩,它们的成岩时代和岩石成因对认识西秦岭岩浆活动和构造演化具有重要意义。对西秦岭多哇地区萨日加岩体进行了详细的野外地质调查、岩相学观察、LA-ICP-MS锆石U-Pb定年和全岩地球化学研究,旨在查明该岩体的年龄、成因类型以及成岩地球动力学背景。结果表明:萨日加岩体由英安斑岩、花岗斑岩及少量石英闪长岩组成;花岗斑岩LA-ICP-MS锆石U-Pb年龄为(238.2±2.6)Ma(平均标准权重偏差(MSWD)为1.7);萨日加岩体属于过铝质高钾钙碱性岩石系列,富集大离子亲石元素Th、Rb、K和轻稀土元素,亏损高场强元素Nb、Ta、Ti等,指示其岩浆源区具有壳幔混合的特征;岩石的主量、微量元素特征显示,英安斑岩属于I型花岗岩,形成于洋-陆俯冲岛弧环境;花岗斑岩倾向于S型花岗岩,形成于大陆碰撞构造环境。由此认为,萨日加岩体形成于晚三叠世西秦岭由洋-陆俯冲岛弧向陆-陆碰撞转变的构造环境。     

胶莱盆地莱阳群杨家庄组沉凝灰岩SHRIMP U-Pb年代学特征及地质意义

胶莱盆地为一发育于华北陆块东部的白垩纪断陷盆地,该次工作主要对盆地底部莱阳群杨家庄组中沉凝灰岩层进行了初步研究,通过对沉凝灰岩岩石学、锆石SHRIMP U-Pb年代学的研究,认为胶莱盆地莱阳群杨家庄组中凝灰岩层形成时代为131.1±1.7Ma,限制了莱阳群杨家庄组的沉积时限,为胶莱盆地早期的形成与演化提供了新的年代学依据。沉凝灰岩中获得单颗碎屑锆石年龄为835±23Ma,指示苏鲁造山带为莱阳群提供了物质来源。     

熊耳裂陷槽云梦山组LA-ICP-MS碎屑岩锆石U-Pb年代学特征及其地质意义

熊耳裂陷槽是华北克拉通开展中—新元古界地质研究的焦点.利用LA-ICP-MS方法,对河南新安黛眉山地区中元古界汝阳群云梦山组进行碎屑岩锆石U-Pb同位素年代学研究,得到80颗锆石的谐和—近谐和年龄.结果表明:云梦山组锆石年龄分布于1 700～2 724 Ma,最年轻的碎屑岩锆石年龄为(1 700±55)Ma,主峰值年龄为2 083 Ma,次峰值年龄为1 771、2 512 Ma;云梦山组的时代下限约为1 700 Ma;物源主要来自中元古代早期或古元古代的岩石,其中来自2.40～1.95 Ga的物源较多;云梦山组样品的碎屑岩锆石年龄峰值与华北克拉通前寒武纪地质事件具有较好的响应关系,分别对应华北克拉通盆地古元古代晚期、中元古代早期的重要地质事件.该结果为研究区的地层对比和年代地层格架建立提供参考.     

银川拜寺口剖面黄旗口组LA-ICP-MS碎屑锆石U-Pb年代学特征及其地质意义

黄旗口组为贺兰山古老结晶基底之上的第一个沉积盖层,其时代归属问题存在争议。利用LA-ICP-MS方法,对银川拜寺口剖面黄旗口组深灰色含海绿石石英细砂岩进行碎屑锆石U-Pb测年分析。结果表明：黄旗口组锆石颗粒以椭球状居多,短柱状次之,外形多呈次圆状和次棱角状,粒径多介于40～130μm;锆石Th/U介于0.12～1.81,其中Th/U大于0.40的占85.3%,以具震荡环带结构的岩浆成因锆石居多,部分锆石后期可能受变质事件改造影响;锆石²⁰⁷Pb/²⁰⁶Pb年龄数据分布范围为1 680～2 606 Ma,存在明显的1 890 Ma主峰值年龄和2 345、2 514、2 576 Ma次级峰值年龄,最小碎屑锆石年龄为(1 680±40)Ma。2 700～2 450、2 040～1 950、1 950～1 800、1 800～1 680 Ma锆石年龄分布对应华北克拉通新太古代克拉通化事件、研究区新生陆弧花岗质岩体主要形成时期、阴山陆块与鄂尔多斯陆块发生碰撞而形成华北西部陆块时期、华北克拉通中元古代基底隆升与陆内裂谷事件。黄旗口组为中元古代长城系晚期沉...     

临武铁砂坪锡石-硫化物矿床地质特征及找矿意义

临武铁砂坪锡石-硫化物矿床位于香花岭多金属矿田内,属断裂充填交代型脉状锡矿床.矿区有锡石-硫化物和锡石-石英脉两种类型锡矿脉,严格受中泥盆统跳马涧组碎屑岩和棋子桥组灰岩中的NE、NW向断裂控制,IV号锡石-硫化物矿脉带长约2 500m,宽500m,平均品位Sn 0.36%,最高品位Sn 1.36%.矿脉产状与容矿断裂产状一致,赋存于棋子桥组的矿体为特殊的深浅相间的条纹岩,它是一种特殊的锡矿工业类型,在湘南地区具有找锡指导意义.     

LA-ICP-MS zircon U-Pb age of rhyolitic lithic-crystal tuffs in Erdaohezi lead-zinc deposit,Inner Mongolia

Erdaohezi lead-zinc deposit belongs to the Derbugan metallogenic belt lying on the northwestern Hailaer-Genhe Mesozoic volcanic basin,located on the western slope of the Da Hinggan Mountains. The deposit is considered as one of the hypabyssal low-temprature hydrothermal lead-zinc deposits associated with volcanism. In order to lay the foundation on studying its diagenesis and mineralization ages,the detailed studies were carried out by dating the host rocks( i. e. rhyolitic lithic-crystal tuffs) using zircon LA-ICP-MS U-Pb method.The dating results show three groups of ages. The first group is the captured zircons( the weighted mean ~(206)Pb /~(238) U age as 175. 6 ± 2. 3 Ma,MSWD = 0. 70,n = 3). The second group can be regarded as the rockforming age( the weighted mean ~(206)Pb /~(238) U age as 165. 3 ± 1. 9 Ma,MSWD = 2. 40,n = 14). The third group should represent the late stage of the magmatic evolution( the weighted mean ~(206)Pb /~(238) U age as 161. 0 ± 3. 1Ma,MSWD = 0. 86,n = 4). According to the ages and the crystal form or CL image characteristics of zircons,it is determined that the diagenesis occurred in the late Middle Jurassic. Based on the regional geology and geochronological research,the acidic pyroclastic rocks are space accompaniment and time connection with the Tamulangou Formation intermediate-mafic volcanic rocks. Both of them constitute the host rocks of the deposit together. The rock combination also provides favorable conditions for large-scale silver,lead and zinc mineralization in this area.     

内蒙古东升庙海西期岩体锆石U-Pb年龄及Hf同位素特征

东升庙岩体位于华北板块北缘西段,岩性主要为白云母二长花岗岩。采用LA-ICPMS锆石U-Pb微区定年和锆石微量
元素及Hf同位素分析方法,对该岩体进行了系统的研究。花岗岩中几乎所有的锆石都显示典型的韵律振荡环带,Th/U比值较
高(均大于0.1),锆石稀土元素球粒陨石标准化配分曲线呈左倾型,并显示明显的正Ce异常和负Eu异常,表明这些锆石为岩浆成
因。测年结果显示,东升庙岩体形成年龄为(259.4±3.3)Ma,代表成岩年龄,属海西晚期侵入岩;部分核部继承锆石年龄加权平均
值为(2367±63)Ma,提供了该区古元古代结晶基底的年龄信息。锆石具有较均一的Hf初始比值,176Hf/177Hf介于0.282125~
0.282362之间,ε_Hf(259Ma)值为较低的负值(-17.3~-9.0),两阶段Hf模式年龄t_DM2为1.91~2.11Ga,指示东升庙岩体起
源于古元古代古老地壳部分熔融。对该岩体的综合研究有助于进一步认识和研究华北板块北缘的构造演化过程。      

Zircon U-Pb geochronology and geochemistry of diorite dikes from Nancha ore deposit in Tonghua area of Jilin and its geological significance

The authors presented geochronology and geochemical data of diorites from Nancha gold deposit in Tonghua region,with the aim to constraining its formation age,magma source and tectonic setting.LA-ICP-MS U-Pb dating results of zircons from the diorites indicate that the rocks were formed in the Middle Jurassic( 171± 2 Ma,MSWD = 1.19).Geochemically,these rocks have Si O_2 concentrations of 52.52%--54.90%,K_2 O of2.14%--3.84%,Na_2 O of 3.17%--3.35%,Mg O of 7.43%--9.34% and high Mg~# of 68.57-72.57.These rocks are characterized by enrichment in large ion lithophile elements( LILE,such as K,Ba,Rb and Sr) and light rare earth elements( LREE),relatively depletion in high field strength elements( HFSE,such as Ta,Nb,Ti and Zr),and heavy rare earth elements( HREE).These characteristics suggest that primary magma of the rocks were derived from the partial melting of mantle with miner crustal contamination,which may related to partial melting of mantle wedge by addition of sediment melt from subducting oceanic crust.Based on former and present studies,the authors consider that the Nancha ore deposit high-Mg diorites were formed in compressional structural setting which is similar to volcanic arc.It could be related to the subduction of the Paleo-Pacific plate beneath the Eurasian continent.     

内蒙古阿巴嘎旗乌和尔楚鲁图钼矿区地质特征及综合找矿信息

乌和尔楚鲁图钼矿是二连-东乌旗成矿带新发现的一处中型隐伏斑岩型钼矿床。根据最新的矿床勘查成果,详细分析了矿床地质特征、物化探异常特征、矿体及矿石特征,简要评述了控矿因素、综合找矿信息。结果表明,矿体主要赋存于花岗斑岩与英安质角砾凝灰熔岩的内外接触带中,呈拱桥状产出。空间上和成因上均与燕山早期侵入的花岗斑岩体关系密切,含矿岩体以富硅、富碱、过铝型以及w(K₂O)>w(Na₂O)为特征。矿区围岩蚀变作用强烈,主要有硅化、钾长石化、黄铁矿化、绢云母化、绿泥石化、碳酸盐化等。主成因类型属低品位斑岩型钼矿床,初步估算钼矿体(3341)资源量为7万多吨。乌和尔楚鲁图钼(铜)矿床的地质、物探、化探等综合找矿信息,对本地区下一步找矿工作的开展具有重要借鉴意义。      

内蒙古阿拉善左旗古腊布陶勒盖金矿地质特征及矿床成因探讨

古腊布陶勒盖金矿床位于阿拉善地块巴彦乌拉山中段,金矿体均受韧性剪切带及EW向、NE向、近SN向断裂控制。赋矿层位为褐红色赤铁矿化绢云母石英糜棱岩,不论是石英脉型金矿,还是蚀变岩型金矿均产于这类岩石中,具有一定的层控特征。矿床经过了中元古代原始沉积地层预富集,后期经过改造富集形成了现在的金矿体。脉内矿物中强烈的热液蚀变和矿石中浸染状、角砾状的构造,显示了岩浆热液矿床的特征。在前人研究的基础上,综合分析区内花岗斑岩和矿床特征,认为古腊布陶勒盖金矿床是古亚洲洋整体于三叠纪闭合、石炭纪末期至三叠纪发育了古亚洲地区规模宏大的成矿事件的响应,矿床类型应为花岗岩叠加改造的韧性剪切带金矿。     

Zircon U-Pb geochronology,geochemistry and petrogenesis of syenogranite from Angeer Yinwula area in Inner Mongolia

The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of syenogranite in Angeer Yinwula area, China, with the aim of determining its formation time, petrogenesis and regional setting. Zircon U-Pb data obtained by LA-ICP-MS indicate that the syenogranite formed in the Early Cretaceous(136.1±0.9 Ma). Geochemically, the rock is characterized by high SiO_2(76.63%--77.58%) and Na_2O+K_2O(8.00%--8.32%), low MgO(0.02%--0.04%) and TFe_2O_3(0.51%--0.84%), and is enriched in LREEs and LILEs, depleted in HREEs and HFSEs. It belongs to high-K calc-alkaline, metaluminous-weakly peraluminous, exhibiting an affinity to I-type granite. All these characteristics implied that the syenogranite in this region derived from crust-mantle mixed source. Overall, the regional geology, geochronology and geochemical features suggest that the formation of the syenogranite was related to the subduction of the Paleo-Pacific Ocean.     

内蒙古自治区翁牛特旗姚家店铅锌矿地质特征

内蒙古自治区翁牛特旗姚家店铅锌矿矿床为一受NW向断裂带构造控制的中低温岩浆热液充填交代型铅锌矿床,形成于燕山晚期,矿体呈脉状产于二叠世额里图组安山质凝灰岩之构造破碎带内,形态产状严格受断裂构造控制。矿石为硅化、黄铁矿化碎裂岩型铅锌矿石。     

Geochemistry,U-Pb,Hf isotopic characteristics and geological significance of Zhalaxiageyong trachydacite in Tuotuohe area,Qinghai

The Zhalaxiageyong lead-zinc-copper polymetallic deposit is a typical porphyry deposit of the Tuotuohe area. Whole-rock geochemical analyses,Zircon U-Pb dating and Hf isotope analysis are undertaken for the ore host trachydacite with the aim of constraining its petrogenesis,magma source and regional tectonic setting.LA-ICP-MS zircon U-Pb dating indicates that the trachydacite was formed in 32. 68 ± 0. 50 Ma( MSWD =1. 6),i. e.,Oligocene. The trachydacite is rich in potassium and poor in Mg#( 5. 10-9. 70),belonging to the peraluminous shoshonite series. The rocks are enriched in LILE( large ion lithophile elements) Rb,Ba,K and LREE,depleted in HFSE( high field strength elements) Nb,Ta,P,Ti,with high Sr and low Y and Yb,having the characteristics of the C type adakite. It is calculated that the initial εHf( t) of the zircons range from-0. 92 to 2. 07 and their two-stage Hf model ages T_(DM2) range from 978 Ma to 1 169 Ma. The magma source should be mainly the partially melt mafic rocks of the thickened Middle Neoproterozoic lower crust of the Northern Qiangtang massif with the addition of ancient aluminosilica material in the melting process. The rocks formed in the tectonic setting of delamination of lithosphere and extension of the thickened crust. During the period of 40-32 Ma,large-scale potassium rich alkaline magmatism occurred in this area. The porphyry metallogenesis is related to the magmatic activities in this period.