华北克拉通北缘中段赤峰撰山子矿区石炭纪-二叠纪侵入岩年代学和地球化学:对古亚洲洋构造演化的制约SCIEI北大核心CSCD

本文对华北克拉通北缘中段赤峰撰山子矿区二长闪长岩、花岗(斑)岩等进行了岩相学、地球化学、锆石U-Pb定年以及Hf同位素研究,以期对古亚洲洋演化形成制约。锆石U-Pb定年显示,二长闪长岩和花岗岩形成于早石炭世(341.0±2.2Ma、324.1±4.3Ma),花岗斑岩形成于晚二叠世(252.8±3.2Ma、252.0±1.5Ma)。岩石地球化学及Hf同位素表明,二长闪长岩为高钾钙碱性I型花岗岩,形成于火山弧环境,其源区可能是俯冲板片脱水交代的地幔楔部分熔融产生玄武质岩浆上涌,导致新生地壳物质的部分熔融,并有部分玄武质岩浆加入形成的产物;花岗岩及花岗斑岩均为高钾钙碱性A型花岗岩,花岗岩形成于火山弧环境,花岗斑岩形成于造山后伸展环境,二者皆为新生地壳部分熔融的产物。综合前人研究认为,早石炭世-晚二叠世,研究区经历了古亚洲洋俯冲、弧-陆碰撞以及造山后伸展等阶段。     

新疆中天山古生代侵入岩浆序列及构造演化

新疆中天山构造岩浆带是中亚造山带的重要组成部分,广泛分布着古生代花岗质侵入体。本研究重点对中天山南缘巴音布鲁克及巴伦台地区的花岗质侵入体进行了LA-ICP-MS锆石U-Pb测年,并获得了岩体侵位年龄由老到新分别为463±3Ma(石英闪长岩)、437±5Ma(石英闪长岩)、424±3Ma(二长花岗岩)、383±4Ma(二长花岗岩)、356±3Ma(二长花岗岩)和303±5Ma(正长花岗岩)。综合区域地质分析认为,中天山古生代侵入岩浆活动可分为四个构造岩浆演化阶段:(1)晚寒武世—晚奥陶世阶段,Terskey洋盆和南天山洋盆自新元古代打开形成广阔洋盆,Terskey洋盆在晚寒武世开始初次俯冲,于晚奥陶世洋盆闭合,南天山洋盆于早奥陶世初次俯冲,具有自西向东、由早到晚的俯冲特点;(2)早志留世—中泥盆世阶段,南天山洋盆持续向北俯冲,该阶段北天山洋开始向南侧俯冲,在伊犁地块北缘形成了弧岩浆;(3)晚泥盆世—早石炭世阶段,南天山洋盆闭合于晚泥盆世末期,在早石炭世中晚期进入残余洋盆演化阶段;(4)晚石炭世—早二叠世阶段,该阶段为后碰撞伸展环境,区域上为陆内演化阶段。     

依连哈比尔尕山石炭纪侵入岩锆石SHRIMP U-Pb测年及其地质意义

博罗科努石炭纪侵入岩为一巨大的岩基,主体岩性为闪长岩,边部发育石英闪长岩、花岗闪长岩、二长花岗岩、花岗岩、斑状花岗岩等,属富含角闪石强-中等钙碱性系列.该岩体的形成主要与板块的俯冲作用有关.在闪长岩中获得锆石SHRIMP U-Pb年龄为308.2Ma±5.4Ma.岩体侵入最新地层为下石炭统大哈拉军山组,为石炭纪活动陆缘火山岩的深成组分,它们共同组成该区的陆缘型岩浆弧,从而说明该区在晚古生代存在古板块的俯冲作用.     

滇西粱河勐养花岗岩的锆石U-Pb年龄、地球化学特征及其地质意义

勐养侵入岩体位于滇西腾冲地块梁河县南勐养镇一带,主要由黑云母二长花岗岩和花岗闪长岩组成,其中发育闪长质包体。闪长岩包体与寄主岩石黑云母二长花岗岩和花岗闪长岩之间呈渐变过渡关系。锆石U-Pb LA-ICP-MS定年表明,黑云母二长花岗岩形成年龄为127.7Ma±0.7Ma,花岗闪长岩形成年龄为115.2Ma±1.1Ma。闪长岩包体形成年龄为122.6Ma±0.8 Ma。表明该花岗岩体的形成时代属于早白垩世。地球化学特征研究表明,闪长岩包体为准铝质、钙碱性系列,具有低SiO2、高MgO、高K20和Mg#的特征。Sm/Nd为0.18～0.20,ΣLREE/ΣHREE=2.91～4.64,Eu存在弱到中等程度的负异常。相对富集U,Th,Rb,Ba等大离子亲石元素(LILE),亏损Tb,Nb,Zr,Hf等高场强元素(HFSE);反映勐养闪长岩包体岩浆成分主要为幔源的特点。根据地球化学特征和微量元素构造判别图解判别结果表明,勐养早白垩世侵入岩形成于碰撞后岩浆弧环境。闪长岩包体的原生岩浆应是地幔橄榄岩部分熔融的产物。黑云二长花岗岩浆可能来源于本区中晚元古代高黎贡山群为代表的地壳物质的部分熔融。花岗闪长岩为幔源岩浆与高黎贡山群古老地壳部分熔融的岩浆混合的产物。腾冲地块早白垩世侵入岩与班公湖—怒江—泸水—瑞丽洋盆的闭合、洋壳向南西俯冲及板块间的碰撞造山作用密切相关。     

柴北缘西段小赛什腾山黑云母二长花岗岩和石英闪长岩岩石成因及其动力学背景：锆石U-Pb年代学、地球化学和Hf同位素约束

位于柴北缘西段的小赛什腾山分布大量海西晚期中酸性岩浆岩,其形成时代和成因类型对揭露区域构造演化具有十分重要的意义。本研究以小赛什腾山二叠纪黑云母二长花岗岩和石英闪长岩作为研究对象,对其进行岩相学、锆石U-Pb年代学、岩石地球化学及Lu-Hf同位素研究。结果表明,黑云母二长花岗岩和石英闪长岩的成岩年龄分别为272±3 Ma和273±2 Ma,指示两者均形成于早—中二叠世。地球化学结果显示,黑云母二长花岗岩属弱过铝质钾玄岩系列I型花岗岩,石英闪长岩为准铝质钙碱性系列I型花岗岩,两者均不同程度富集大离子亲石元素Rb、Th、K等,亏损Nb、Ta、Ti等高场强元素,具有典型的弧岩浆地球化学特征。锆石Lu-Hf同位素表明黑云母二长花岗岩具正的ε_Hf(t)值(2.04～8.16)和较年轻的二阶段Hf模式年龄(t_DM2=0.77～1.16 Ga)。结合前人研究成果,认为小赛什腾山早—中二叠世黑云母二长花岗岩和石英闪长岩均为宗务隆洋俯冲消减的产物,石英闪长岩为玄武质洋壳板片发生部分熔融产生的熔体遭受地幔橄榄岩混染而成,而黑云母二长花岗岩为洋壳熔融产生的岩浆底侵...     

柴达木盆地北缘古生代超高压带中花岗质岩浆作用

祁连南缘古生代超高压变质带 (榴辉岩年龄为 4 6 6～ 4 95 Ma)上一套中高级变质岩系 (达肯大坂片麻岩 )中存在三类花岗岩组合 : 类 :石英二长闪长岩 -花岗闪长岩 -二长花岗岩 , 类 :二长花岗岩 -二云母花岗岩-含白云母花岗岩 -正长花岗岩 , 类 :花岗闪长岩 -二长花岗岩 -黑云母花岗岩。 类岩石组合中的二长花岗岩锆石SHRIMP年龄为 4 73Ma, 类岩石组合中的正长花岗岩锆石 SHRIMP年龄为 4 4 6 Ma, 类岩石组合中的二长花岗岩锆石 SHRIMP年龄为 397Ma。从三类花岗岩组合的组成矿物来看 , 类和 类的矿物组合主要为斜长石、角闪石、石英、碱性长石、黑云母 , 类的矿物组合为钾长石、石英、白云母、黑云母、斜长石 ;从岩石地球化学特征上看 , 类和 类花岗岩为 型花岗岩 ,岩石的 Si O2 =6 1%～ 6 9% ,Na2 O/ K2 O>1,ANK<1,δEu=0 .7～ 1.0 ; 类花岗岩为 S型花岗岩 ,岩石的 Si O2 =70 %～ 76 % ,Na2 O/ K2 O<1,ANK>1,δEu=0 .1～ 0 .3;从构造环境上看 , 类花岗岩形成于岛弧环境或活动大陆边缘 , 类花岗岩形成于同碰撞 , 类花岗岩形成于碰撞后。结合区域地质特征 ,我们认为 ,早奥陶世 ,南祁连洋板块向北俯冲于祁连陆块之下 ,规模不大的南祁连洋很快闭合 ,但俯冲下去的大洋板块仍拖动柴达木陆块继续俯冲 ,俯冲     

西昆仑西段晚古生代—中生代花岗质岩浆作用及构造演化过程

本文通过对西昆仑西段地区晚古生代—中生代花岗岩的岩石类型、形成时代和岩石地球化学资料的综合分析,探讨花岗质岩浆活动期次、岩石成因,结合区域资料,探讨构造-岩浆演化特征和碰撞造山过程。将该地区晚古生代—中生代构造-岩浆演化分为7个阶段:(1)388~324 Ma(特提斯Ⅰ、Ⅱ支洋向北俯冲消减阶段),具富钠贫钾特征的低温TTG岩石组合,形成于陆缘弧环境;(2)339~291 Ma(奥依塔格弧后盆地演化阶段),由于南部特提斯Ⅰ支洋持续往北俯冲,导致西昆仑北缘发生弧后扩展而形成弧后盆地,形成拉斑质具强烈富钠贫钾特征的低温大洋花岗岩;(3)258~241 Ma(特提斯Ⅰ支洋闭合、碰撞造山阶段),岩石中发育石榴子石和白云母,普遍具片麻状构造,属于S型花岗岩,陆壳部分熔融的产物;(4)234~210 Ma(特提斯Ⅰ后碰撞伸展阶段):岩体规模较大,为I型→A型花岗岩,伴随着地幔岩浆底侵和强烈的壳幔岩浆混合作用;(5)198~150 Ma(特提斯Ⅱ支洋向南俯冲消减阶段):类似TTG的岩石组合,形成于与洋壳俯冲有关的岩浆弧环境;(6)148~118 Ma(特提斯Ⅱ支洋闭合、碰撞造山阶段):弱片麻状二云二长花岗岩,属C型埃达克岩,为陆-陆碰撞过程中陆壳加厚发生部分熔融的产物;(7)111~75 Ma(特提斯Ⅱ后碰撞伸展阶段):发育规模较大,钾玄质系列,是古老地壳部分熔融的产物。根据各阶段花岗质岩浆活动特征和构造演化过程,初步提出了西昆仑西段晚古生代—中生代大地构造演化模式图。     

北阿尔金地区早古生代洋壳俯冲时限:来自斜长花岗岩和花岗闪长岩的证据

蛇绿岩在不同演化阶段自身形成的花岗质岩石和侵入到蛇绿岩中的花岗质岩石对于蛇绿岩的精确定年具有重要意义,是揭示洋壳俯冲时限的有力证据。对北阿尔金红柳沟—拉配泉蛇绿岩中斜长花岗岩和花岗闪长岩的锆石U-Pb及Lu-Hf同位素分析表明,红柳沟斜长花岗岩和花岗闪长岩的锆石LA-ICP-MS U-Pb定年结果分别为(501±3)Ma和(496±2)Ma,表明北阿尔金洋的俯冲时限可能开始于中寒武世或更早。斜长花岗岩和花岗闪长岩的锆石εHf(t)值均为正值,结果分别为1.6~5.6和3.3~6.9,反映其源区均为亏损型地幔。全岩地球化学分析结果表明,斜长花岗岩具有高Si O2、高Sr、低Y和相应的高Sr/Y等类似于埃达克质岩石的特征,可能来自热的洋壳俯冲到石榴角闪岩相条件下变基性岩发生小比例部分熔融形成,且其形成深度应该在40~50 km;花岗闪长岩属于高钾钙碱性系列岩石,可能代表了岛弧环境下下地壳基性岩石部分熔融的产物。年代学分析表明,北阿尔金洋可能存在南北双向俯冲,并且北阿尔金洋向北俯冲可能略早于向南俯冲。北阿尔金和北祁连的俯冲时限对比研究表明,北阿尔金早古生代缝合带是北祁连早古生代缝合带的西延部分。     

西藏双湖纳若地区花岗闪长岩LA-ICP-MS锆石U-Pb年龄与地球化学特征

龙木错—双湖缝合带内呈东西向断续分布大小不等的花岗岩,1∶25万区域地质调查研究结果显示,该花岗岩时代为早—晚侏罗世。本文对双湖纳若地区原为早侏罗世的花岗闪长岩2件样品进行了LA-ICP-MS锆石U-Pb测年,获得年龄为215.1±1.8Ma、217.0±1.5Ma,属晚三叠世。岩石地球化学研究表明,花岗岩闪长岩属偏铝质—过铝质高钾钙碱性花岗,轻、重稀土元素分馏较明显,高场强元素Nb、Ta、Ti强烈的亏损。形成于龙木错—双湖古特提斯洋闭合后陆—陆碰撞晚期的后碰撞阶段的伸展环境,以龙木错—双湖缝合带所代表的特提斯洋岩石圈向北俯冲,伴随之后的俯冲板片的断离,软流圈物质上涌,压力减低,温度升高,促使地壳物质发生了部分熔融,花岗闪长岩就是地壳物质部分熔融的产物。     

内蒙古狼山地区早石炭世石英闪长岩U-Pb年龄、地球化学特征及其对古亚洲洋俯冲的指示

内蒙古狼山山脉西侧分布大面积的晚古生代岩浆岩,时代集中在早石炭世—晚二叠世,早石炭世石英闪长岩体出露于潮格温都尔镇西侧。该岩体岩性为石英闪长岩,LA-ICP-MS锆石U-Pb年龄显示,石英闪长岩的~(206)Pb/~(238)U年龄加权平均值为337.4±6.6 Ma。岩石暗色矿物以角闪石为主,黑云母次之,富铁,富钠,高钠钾比值,为钙碱性系列;富集大离子亲石元素Rb、K、Pb,不同程度的亏损高场强元素Nb、Ta、P、Ti的特点,稀土元素配分型式为轻稀土元素富集,重稀土元素亏损,弱的负Eu异常,总体反映岩浆弧的地球化学特征。构造环境判别图显示样品点落在大陆边缘弧范围,岩石地球化学特征表明狼山地区早石炭世处于大陆边缘弧构造背景,古亚洲洋石炭纪存在向南俯冲。对比北部造山带西乌旗地区的早石炭世石英闪长岩,两者地球化学特征基本相同。因此,早石炭世古亚洲洋发生了双向俯冲,形成了以石英闪长岩为主的岩石类型。     

Geochronology in the southern Midyan terrane: a review of constraints on the timing of magmatic pulses and tectonic evolution in a northwestern part of the Arabian Shield

The southern Midyan terrane is a composite Tonian to Ediacaran tectonostratigraphic crustal block in the northern Arabian Shield that prior to Red Sea opening was contiguous with coeval rocks in the Eastern Desert of Egypt and Sinai. Ion microprobe (sensitive high-resolution ion microprobe [SHRIMP]) dating of 12 rock samples described here and the results of other dating programmes establish a clear timeframe for depositional, intrusive, and structural events in the region and provide a chronology of tectonism in this part of the Arabian-Nubian Shield. Deposition of Zaam and Bayda group volcanosedimentary rocks and emplacement of mafic-ultramafic complexes and TTG-type diorite, tonalite, and granodiorite denote formation of the Tonian (780–715 Ma) Zaam arc and fore-arc ophiolite above a possible west-dipping subduction system in the southern part of the Midyan terrane. Convergence with the Hijaz terrane farther south and obduction of ophiolite nappes resulted by ~700 Ma in development of the Yanbu suture. Ongoing or a new subduction system led to a ~705–660 Ma Cryogenian pulse of magmatism represented by I-type calc-alkaline diorite, granodiorite, and granite that have volcanic-arc and syn-collisional granite affinities. This was followed, after a brief end-Cryogenian hiatus, by a 635–~570 Ma period of Ediacaran magmatism marked by monzogranite, syenogranite, and minor gabbro and diorite. These rocks are reported to have within-plate to volcanic-arc and syncollision chemical characteristics but their precise tectonic setting is uncertain. Structurally, the intrusions are diapiric and were evidently emplaced in an extensional regime consistent with an overlap between intrusion and Najd faulting associated, at this time, with transpressional collision and northward extension through much of the ANS. Terminal magmatism in the southern Midyan terrane postdated cessation of Najd faulting at ~575 Ma and resulted in the emplacement of undeformed within-plate A-type alkali-feldspar granites and mafic (lamprophyre) and felsic dikes.     

An early Palaeozoic double-subduction model for the North Qilian oceanic plate: evidence from zircon SHRIMP dating of granites

The North Qilian Orogenic Belt (NQOB), which consists of ophiolitic mélange and island-arc assemblages containing many granites, blueschists, and eclogites, lies between the Alax and Qilian terranes in northwestern China. The Minleyaogou and Niuxinshan granitoids occur at the northern and southern margins, respectively, in the middle segment of the NQOB. The Minleyaogou pluton is granodiorite in composition, whereas the Niuxinshan pluton consists mainly of red granite with minor grey quartz diorite. Geochemically, the Minleyaogou granite differs from the Niuxinshan granite in that it contains a smaller range in SiO₂, has lower total alkalis, and is more peraluminous. Both granitoids are magnesian but the Niuxinshan granite is alkali-calcic, whereas the Minleyaogou granodiorite is calcic. Both granitoids have similar chondrite-normalized rare earth element patterns with light rare earth element enrichment and negative Eu anomalies. They have pronounced negative Ba, Nb, Sr, P, and Ti anomalies indicating that they have an affinity to island-arc or active continental margin magmatism. SHRIMP U–Pb dating of zircons from the granitoids yields a formation age of 477 Ma for the Niuxinshan granite and 463 Ma for the Minleyaogou granodiorite. These ages, combined with the geochemistry and locations of the plutons, suggest that they formed by the double subduction of the North Qilian oceanic plate during early Palaeozoic time. Formation of the Niuxinshan granite may be related to southward subduction under the Qilian terrane at 477 Ma, whereas the Minleyaogou granodiorite was formed by northward subduction at 463 Ma under the Alax terrane.     

太行山阜平杂岩中麻棚-赤瓦屋岩体的时代、侵位深度及构造意义

中生代岩浆活动在太行山北段形成了一系列花岗岩体,其中的麻棚-赤瓦屋岩体侵位于穹窿状的阜平杂岩中,具有贫硅、富碱、高铝的钙碱性I型花岗岩特征。岩体分带明显,由边部向核部可以划分为石英闪长岩、花岗闪长岩、似斑状花岗岩3个相带,它们的锆石LA-ICP-MS U-Pb年龄分别为126.4±2.4 Ma、125.4±2.0 Ma和126.2±2.0 Ma,在误差范围内一致,指示岩体在早白垩世期间快速侵位、结晶。各相带样品的角闪石全铝平均值分别为1.018、0.880和0.871,对应的角闪石平均结晶压力分别为0.183、0.118和0.114 GPa,均值为0.141 GPa,对应的侵位深度约5 km,明显小于区域内元古界至侏罗系的地层厚度,表明在岩体侵位之前,阜平杂岩就已经具有穹窿状构造特征。结合相关资料,估计太行山早白垩世以来的平均隆升速率为0.07~0.08 km/Ma。     

Late Mesozoic magmatism in the Jiaodong Peninsula,East China:Implications for crust-mantle interactions and lithospheric thinning of the eastern North China Craton

A section from the Linglong gold deposit on the northwestern Jiaodong Peninsula,East China,containing Late Mesozoic magmatic rocks from mafic and intermediate dikes and felsic intrusions,was chosen to investigate the lithospheric evolution of the eastern North China Craton(NCC).Zircon U-Pb data showed that low-Mg adakitic monzogranites and granodiorite intrusions were emplaced during the Late Jurassic(～145 Ma) and late Early Cretaceous(112-107 Ma),respectively;high-Mg adakitic diorite and mafic dikes were also emplaced during the Early Cretaceous at～139 Ma and ～118 Ma,and 125-145 Ma and 115-120 Ma,respectively.The geochemical data,including whole-rock major and trace element compositions and Sr-Nd-Pb isotopes,imply that the mafic dikes originated from the partial melting of a lithospheric mantle metasomatised through hydrous fluids from a subducted oceanic slab.Low-Mg adakitic monzogranites and granodiorite intrusions originated from the partial melting of the thickened lower crust of the NCC,while high-Mg adakitic diorite dikes originated from the mixing of mafic and felsic melts.Late Mesozoic magmatism showed that lithosphere-derived melts showed a similar source depth and that crust-derived felsic melts originated from the continuously thickened lower crust of the Jiaodong Peninsula from the Late Jurassic to Early Cretaceous.We infer that the lower crust of the eastern NCC was thickened through compression and subduction of the Palaeo-Pacific plate beneath the NCC during the Middle Jurassic.Slab rollback of the plate from ～160 Ma resulted in lithospheric thinning and accompanied Late Mesozoic magmatism.     

吉林延边小西南岔铜（金）矿床早白垩世中—酸性岩浆岩年代学、地球化学及其成因探讨

小西南岔铜（金）矿床位于吉林省延边地区东部,通过对小西南岔铜（金）矿床早白垩世中—酸性岩浆岩进行野外地质、岩相学、年代学和地球化学等方面的研究,进一步探讨延边乃至东北地区中生代大地构造演化。年代学研究结果表明：其同位素年龄分别为(101.69±0.61) Ma（石英闪长岩）、(101.14±0.58) Ma（英云闪长岩）、(100.82±0.62) Ma（花岗闪长岩）和(100.20±1.10) Ma（闪长玢岩）,岩浆作用发生在早白垩世末期（102~100 Ma）,是同一构造演化过程的产物。岩石地球化学研究表明,闪长玢岩具有典型埃达克质岩石的地球化学特征,其w(SiO₂)=61.419%~62.153%,w(Al₂O₃)=16.872%~17.329%,w(MgO)=2.339%~2.643%,w(Na₂O)=5.749%~6.623%,w(K₂O)=1.483%~1.786%,w(Sr)=(691~888)×10^-6,w(Yb)=(0.71~0.83)×10^-6,Sr/Y值为87.4~120.0,LREE富集,说明闪长玢岩是由俯冲的大洋板片部分熔融产生的埃达克质岩浆上侵就位形成。埃达克质岩浆上侵过程中与下地壳重熔产生的酸性岩浆混合,形成的富集地幔源岩浆上侵就位形成石英闪长岩、英云闪长岩和花岗闪长岩等钙碱性花岗质杂岩;岩浆热液沿区域断裂上升过程中与大气降水混合,萃取围岩中的成矿物质,形成富铜（金）组分的成矿热液,在合适的部位卸载沉淀形成脉状铜（金）矿化。晚中生代延边地区位于古太平洋板块向欧亚大陆板块俯冲的大陆边缘环境,古太平洋板块的俯冲是形成早白垩世石英闪长岩、英云闪长岩、花岗闪长岩和闪长玢岩（脉）以及小西南岔矿床热液脉型铜（金）矿化的直接动力来源。     

内蒙古突泉—科尔沁右翼中旗地区中生代花岗岩锆石U-Pb年龄及其地质意义

内蒙古突泉—科尔沁右翼中旗地区位于大兴安岭中南段,中生代岩浆活动较为频繁,岩浆作用形成的岩石类型主要包括花岗闪长岩、正长花岗岩、二长花岗岩和花岗斑岩等。鉴于目前研究区地质资料缺乏对整个突泉—科右中旗地区中生代花岗岩较为完善的研究和论述,笔者旨在对全区范围内的中生代花岗岩进行LA-ICP-MS锆石U-Pb年龄测定,同时在总结前人资料的基础上划分该地区不同的中生代岩浆作用期次,进而讨论本区不同花岗岩所代表的地质意义。花岗岩锆石U-Pb年龄测试结果表明,孟恩陶勒盖花岗闪长岩的形成时代为（241.2±2.8） Ma,杜尔基镇南部正长花岗岩的形成时代为（148.2±1.0） Ma,宝格吐岩体的花岗闪长岩的形成时代为（226.0±1.1） Ma,马家屯花岗斑岩的形成时代为（124.6±1.1） Ma,这与广泛分布于本区中生代火山岩的形成时代较为一致。结合前人研究成果以及邻区的地质资料,认为本区岩浆活动可以划分为中—晚三叠世、晚侏罗世和早白垩世;中—晚三叠世花岗岩可能属于古亚洲洋闭合造山后岩石圈伸展作用的产物,而晚侏罗世花岗岩的形成可能与中侏罗世蒙古—鄂霍茨克洋闭合后岩石圈伸展作用有关,早白垩世花岗岩可能反映了板内拉张的构造背景。     

豫西火神庙岩体锆石U-Pb年代学、地球化学及Hf同位素组成

火神庙岩体位于华北陆块南缘栾川矿集区西部,为一杂岩体,该岩体与火神庙钼矿床密切相关.目前,人们对火神庙岩体的研究程度较低,严重制约了对火神庙钼矿床成因的认识.系统开展了年代学、地球化学和Hf同位素组成研究.结果表明,石英闪长岩、二长花岗岩和花岗斑岩的形成年龄分别为150.3±0.6Ma、146.0±0.6Ma和145.1±0.5Ma,为栾川矿集区晚侏罗世第2次大规模岩浆活动的产物.火神庙杂岩体属于I型花岗岩,是不同源区部分熔融形成的岩浆上升就位的结果.石英闪长岩是富集岩石圈地幔部分熔融的产物;二长花岗岩和花岗斑岩是富集岩石圈地幔部分熔融形成的镁铁质岩浆与太华群TTG岩系部分熔融形成的长英质岩浆混合后上升就位的结果.      

西藏嘎拉勒铜金矿床的成岩成矿时代与岩石成因:锆石U-Pb年龄、Hf同位素组成及辉钼矿Re-Os定年

西藏嘎拉勒铜金矿床作为构造背景反演指示针的成岩成矿年代学研究较为匮乏,使得该成矿带区域背景-构造-岩浆-成矿活动系列研究步履维艰,利用LA-ICP-MS(laser ablation inductively coupled plasma mass spectrometry)锆石U-Pb测年、辉钼矿Re-Os定年及Lu-Hf同位素技术,首次全面厘定了区内侵入岩侵位时序、探讨了岩石成因并确定了成矿时代.结果表明,成矿前闪长岩成岩年龄为155.8±2.3 Ma,侵位于晚侏罗世初期,ε_Hf(t)值分布于-14.68~-8.34,平均值-11.74,是班公湖-怒江特提斯洋南向俯冲的产物;花岗闪长岩为矿区成矿母岩,其成岩年龄为88±1 Ma(MSWD=0.56,n=21),ε_Hf(t)值分布于5.84~9.20,平均值7.72,成矿后花岗斑岩成岩年龄为84.67±0.80 Ma(MSWD=1.9,n=18),ε_Hf(t)值分布于6.32~9.78,平均值8.40,二者均为晚白垩世侵位,为拉萨地体与羌塘地体汇聚的产物;矿区辉钼矿Re-Os等时线年龄为88.55±0.60 Ma(MSWD=0.60,n=8),与成矿母岩(花岗闪长岩)成岩年龄一致.研究表明,在班公湖-怒江特提斯洋南向俯冲至碰撞过程中在矿区内均有相应的岩浆活动响应,嘎拉勒铜金矿床则为典型的碰撞期成矿作用的产物.      

Two periods of mineralization in Xiaoxinancha Au–Cu deposit,NE China: evidences from the geology and geochronology

The Xiaoxinancha Au–Cu deposit is located at the eastern segment of the Tianshan–Xingmeng orogenic belt in northeast China. The deposit includes porphyry Au–Cu orebodies, veined Au–Cu orebodies and veined Mo mineralizations. All of them occur within the diorite intrusion. The Late Permian diorite, Late Triassic granodiorite, Early Cretaceous granite and granite porphyry are developed in the ore area. The studies on geological features show that the porphyry Au–Cu mineralization is related to the Late Permian diorite intrusion. New geochronologic data for the Xiaoxinancha porphyry Au–Cu deposit yield Permian crystallization zircon U–Pb age of 257 ± 3 Ma for the diorite that hosts the Au–Cu mineralization. Six molybdenite samples from quartz + molybdenite veins imposed on the porphyry Au–Cu orebodies yield an isochron age of 110.3 ± 1.5 Ma. The ages of the molybdenites coeval to zircon ages of the granite within the errors suggest that the Mo mineralization was genetically related to the Early Cretaceous granite intrusion. The formation of the diorite and the related Au–Cu mineralization were caused by the partial melting of the subduction slab during the Late Palaeozoic palaeo‐Asia Ocean tectonic stage. The Re contents and Re–Os isotopic data indicate that the crustal resource is dominated for the Mo mineralization during the Cretaceous extensional setting caused by the roll‐back of the palaeo‐Pacific plate. Copyright © 2014 John Wiley & Sons, Ltd.     

Ages of the Laocheng Granitoids and Crustal Growth in the South Qinling Tectonic Domain, Central China: Zircon U-Pb and Lu-Hf Isotopic Constraints

The Laocheng granitoid pluton is located in the South Qinling tectonic domain of the Qinling orogenic belt,southern Shaanxi Province,and consists chiefly of quartz diorite,granodiorite and monzogranite.A LA-ICP-MS zircon U-Pb isotopic dating,in conjunction with cathodoluminescence images,reveals that the quartz diorite and granodiorite were emplaced from 220 Ma to 216 Ma,while the monzogranite was emplaced at～210 Ma.In-situ zircon Hf isotopic analyses show that theε_(Hf)(t) values of the quartz diorite a...