滇东南薄竹山花岗岩的LA-ICP-MS锆石U-Pb定年及地质意义

通过对滇东南薄竹山花岗复式岩体3个代表性花岗岩样品的LA-ICP-MS锆石U-Pb同位素年龄测试,获得了该岩体的形成时代。其中,雷达站单元样品的²⁰⁶Pb-²³⁸U加权平均年龄为（86.51±0.52） Ma(MSWD值为2.4);所作底单元样品的²⁰⁶Pb-²³⁸U 加权平均年龄为（87.54±0.65）  Ma(MSWD值为1.6);洋芋树单元样品的²⁰⁶Pb-²³⁸U 加权平均年龄为（87.83±0.39）  Ma (MSWD值为0.15)。这些分布比较集中的年龄数据为薄竹山花岗岩体提供了一个准确的形成时限。这些年龄数据表明,薄竹山花岗岩体同区域内的其它岩浆岩和与之相关的个旧、大厂、都龙超大型锡多金属矿床等都是晚白垩世的产物,均为华南西部地区岩浆-成矿带的重要组成部分,也是华南西部晚白垩世大规模成岩成矿作用在滇东南地区的又一具体表现。     

内蒙古道伦达坝铜钨锡矿床LA-ICP-MS锆石和锡石U-Pb年龄及其地质意义

道伦达坝矿床位于大兴安岭南段,是一个铜钨锡矿床,其铜、钨、锡储量均达中型。矿体呈脉状,主要产于二叠系砂板岩中的断裂破碎带中,华力西期黑云母花岗岩中的断裂破碎带中亦赋存有矿体。文章选取2件石英-萤石-白云母-电气石-锡石-黑钨矿阶段的矿石样品对其中的进行了LA-ICP-MS U-Pb定年,获得2件样品的~(207)Pb/~(206)Pb-~(238)U/~(206)Pb谐和年龄分别为(134.7±6.6)Ma(MSWD=1.4)和(136.8±7.4)Ma(MSWD=1.7),~(206)Pb/~(207)Pb-~(238)U/~(207)Pb等时线年龄分别为(132±12)Ma(MSWD=0.76)和(135±13)Ma(MSWD=0.9)。锡石定年结果表明,道伦达坝矿床形成于早白垩世。对矿区外围张家营子岩体中的斑状细粒花岗岩进行了LA-ICP-MS锆石U-Pb测年,获得的~(206)Pb/~(238)U加权平均年龄为(135±1)Ma(MSWD=1.3),该岩体的形成年龄与道伦达坝矿床的成矿年龄在误差范围内一致。本次定年结果表明道伦达坝矿床形成于早白垩世,与同期的花岗质岩浆活动有密切的成因联系,该矿床属于与花岗岩有关的岩浆热液脉型矿床。     

内蒙古大井矿区及外围岩浆岩锆石U-Pb年龄及其对成矿时间的约束

大井是内蒙古东部地区的一处大型铜银锡多金属矿床,矿体呈脉状产出在二叠系林西组地层中,受NW或NWW向断裂控制。本文对大井矿区及其外围主要侵入岩体和火山岩开展了年代学和地球化学研究。LA-MC-ICP-MS锆石测年结果表明,大井矿区内靠近1号矿脉产出的2件霏细岩脉样品的锆石年龄分别为170.7±1.4Ma(MSWD=1.9)和170.7±1.1Ma(MSWD=1.3);矿区外围马鞍子黑云母二长花岗岩体的锆石年龄为279.7±1.3Ma(MSWD=0.74);唐家营子附近安山玢岩脉的锆石年龄为252.0±1.8Ma(MSWD=1.6);大四段村似斑状黑云母二长花岗岩体的锆石年龄为242.8±1.7Ma(MSWD=1.7);采自大坝南部的流纹质晶屑熔结凝灰岩、流纹质火山角砾熔岩和晶屑凝灰岩的锆石年龄分别为143.5±0.7Ma(MSWD=0.38),144.3±0.7Ma(MSWD=1.2)和145.3±1.0Ma(MSWD=2.5);小城子村南部石英斑岩脉的锆石年龄为146.1±0.9Ma(MSWD=1.7),安山玢岩脉的锆石年龄133.2±0.7Ma(MSWD=0.96)。反映本区至少存在四期岩浆活动,分别是海西晚期、印支早期、燕山早期和燕山中期。岩石地球化学分析结果表明,大井矿区及外围主要侵入岩(黑云母二长花岗岩、似斑状黑云母二长花岗岩、霏细岩、安山玢岩和石英斑岩)均为富SiO₂、富碱、准铝的钙碱性岩石,在SiO₂-K₂O图解上均落入"高钾钙碱系列"区。所有的岩石样品具有轻稀土分异明显、富集大离子亲石元素(LILE)的特征,其中Ba、Nb、Sr、P、Ti相对亏损,而Rb、Th、K、Ce、Nd、Hf、Sm、Y 和Yb相对富集。侵入岩和火山岩的年代学与岩石地球化学特征表明,马鞍子黑云母二长花岗岩和大四段村似斑状黑云母二长花岗岩的侵位可能与古亚洲洋的碰撞闭合有关,形成于挤压的构造环境;燕山早期侵入岩在本区并不发育,其形成环境还有待进一步查明,可能与西伯利亚板块和蒙古-华北板块之间的鄂霍茨克洋消亡及后碰撞造山有关;而燕山晚期大规模的侵入-火山喷发活动可能是由岩石圈减薄,区域大规模伸展所引起。根据本文对矿区内及外围侵入岩与火山岩的年代学研究,结合矿区地质和前人研究成果,认为大井铜银锡矿床的成矿主要与晚侏罗世-早白垩世岩浆活动(146~133Ma)有关,是区域伸展构造背景下岩浆活动的产物。     

滇西哀牢山变质岩系锆石U-Pb定年及其地质意义

哀牢山-红河构造带是滇西地区最著名的带状变质带之一,其主体由哀牢山深变质岩系(哀牢山岩群)组成,一直被认为是扬子陆块古元古代结晶基底.本文选取哀牢山深变质岩系内的花岗片麻岩(11 ALl7-1和11AL09-1)和石英岩(11AL08-1),以及邻区的花岗岩(11ALl2-1)进行LA-ICP-MS锆石U-Pb定年.结果显示,花岗片麻岩11 ALl7-1有岩浆和变质两类锆石,两者的206Pb/238U年龄加权平均值分别为700±6Ma(MSWD=1.4,n=14)和27.4±1.2Ma(MSWD=1.9,n=3),代表原岩形成时代和变质年龄.花岗片麻岩llAL09-1岩浆锆石206 pb/238U年龄为220±3Ma(MSWD=3.1,n=14),变质锆石年龄为31.2±2.3Ma(MSWD =6,n=5),分别代表原岩结晶时代和后期变质年龄.石英岩11AL08-1中所有锆石具有核-边结构,92颗锆石核部年龄集中分布在6组,分别为493～528Ma(n=42)、635 ～ 640Ma(n=2)、701～784Ma(n=44)、976 ～980Ma(n=2)、1839Ma(n=1)和2487Ma(n=1).92个核部分析点具有高的Th/U比值(＞0.23),指示岩浆来源.最年轻一组的42个核部年龄加权平均值为509Ma,代表石英岩原岩的最大沉积时代.7颗锆石变质边年龄为26～ 75 Ma内,代表变质年龄.花岗岩11 ALl2-1锆石206pb/238U年龄加权平均值为750±4Ma(MSWD =0.6),代表岩石形成时代.这些年龄表明哀牢山变质岩系是一个原岩复杂的变质杂岩带,它的原始物质至少包含新元古代～ 700Ma岩浆岩、～509 Ma沉积地层及220 ～ 240Ma的岩浆岩和地层,而不是以往认为的古元古代结晶基底.现今所见的哀牢山岩群“古老”岩石面貌主要是由地质历史上的浅变质或未变质的地层和岩浆岩在新生代26～31Ma发生变质变形作用改造的结果.哀牢山变质带的源区物质特征和主要岩浆事件与扬子陆块西缘十分相似,具有亲扬子的构造属性.     

豫南团山花岗岩LA-MC-ICP-MS锆石U-Pb年龄及其地质意义

豫南团山花岗岩是灵山岩体的一个独立单元,具有含斑细粒黑云二长花岗岩和细粒黑云二长花岗岩两种岩性,是在灵山序列主岩浆期后形成的第一个补充期产物,也是最大规模的补充期产物,基本代表了灵山花岗岩的形成年龄下限。为了限定此年龄和研究灵山岩体与紧邻的肖畈小岩体的关系及其形成的构造背景,对团山花岗岩的两种岩石进行锆石LA-MC-ICP-MS U-Pb年龄测试,并结合前人研究成果综合论述了团山花岗岩的基本地质特征。测试结果显示团山独立单元两种岩性的形成时间分别为129.90±0.63 Ma(MSWD=0.78)和129.92±0.61 Ma(MSWD=0.74),两种岩性形成时间基本一致。灵山岩体晚于肖畈岩体近10 Ma形成,推测两者为两期不同的岩浆活动产物。灵山及其附近早白垩世花岗岩体均具有与区域韧性断裂带形迹方向基本一致的北西-北西西轴线和接触界线,可作为扬子板块与华北板块碰撞事件和断裂事件的岩浆活动响应的证据。此外,通过分析收集到的灵山岩体年龄测试数据发现灵山岩体的形成年龄集中分布于95～110 Ma、120～135 Ma,推测灵山岩体在形成过程中可能经历了两次大的岩浆活动。     

藏东吉塘复式花岗岩成因——来自锆石U-Pb年龄和地球化学的证据

吉塘复式花岗岩位于澜沧江岩浆岩带北段,是研究澜沧江结合带演化过程的重要窗口。对澜沧江北段卡贡地区吉塘复式花岗岩中的黑云母二长花岗岩和花岗闪长岩开展了LA-ICP-MS锆石U-Pb年代学、岩石地球化学研究。研究结果表明,所选锆石样品均具有明显的生长环带,Th/U值普遍大于0.4,为典型的岩浆锆石,分别获得锆石~(206)Pb/~(238)U年龄加权平均值为222.8±1.5Ma(MSWD=1.60,n=16)、213.6±1.1Ma(MSWD=0.98,n=20)和221.1±1.5Ma(MSWD=1.30,n=15),时代均属于晚三叠世。岩石地球化学特征表明,吉塘黑云母二长花岗岩和花岗闪长岩具有较一致的主量、微量元素含量,其变化特征也具有一致性,反映这2类岩石可能为同一期岩浆演化而来;吉塘复式花岗岩属于过铝质S型花岗岩,与临沧花岗岩、纽多花岗岩具有一致的岩石地球化学性质,为澜沧江花岗岩带的重要组成部分,具有统一的构造岩浆活动模式;吉塘复式花岗岩的成因与碰撞造山导致地壳加厚增温及与岩石圈剪切、伸展期有关的深熔作用有关,澜沧江洋的闭合时间可能为273Ma左右。     

西南天山科桑溶洞新元古代-早奥陶世花岗岩锆石U-Pb年代学研究

在新疆西南天山科桑溶洞地区,新厘定出一套斜长角闪岩-花岗岩地质单元:侵入斜长角闪岩中的新元古代白云母花岗岩(片麻状构造)、以及侵入上述古老岩石单元的早奥陶世花岗岩(块状构造)。片麻状白云母花岗岩中锆石具有热液锆石边、岩浆锆石幔和碎屑锆石核(边-幔-核结构),剔除被热液锆石和碎屑锆石混染的SHRIMP测点,获得岩浆锆石幔的加权平均年龄752.3±5.1Ma(MSWD=0.95),代表岩浆的结晶年龄。块状花岗岩的锆石具有边-核结构,热液锆石边的U-Pb年龄(419.5±5.7Ma)明显偏低。剔除热液锆石和碎屑锆石,获得岩浆锆石的平均U-Pb年龄481.1±4.4Ma(MSWD=0.88),代表花岗岩的结晶年龄。早奥陶世早期,岩浆侵入新元古代片麻状白云母花岗岩中。在晚志留世或者更晚时期,两类花岗岩共同经受了变质热液改造,变质流体交代岩浆锆石,导致锆石溶蚀再生长。     

内蒙古丰镇市泉子沟斑岩钼矿床成岩成矿年代学及其地质意义

泉子沟斑岩钼矿床位于内蒙古丰镇市,地处华北克拉通北缘内蒙古台隆凉城断隆内。矿区出露一套燕山期花岗质杂岩体——红娘山杂岩体,主要由中粗粒花岗岩、似斑状花岗岩和石英斑岩组成,钼矿体主要赋存于似斑状花岗岩中。文章在详细的野外地质调查基础上,对泉子沟矿床的成岩成矿时代进行了详细研究,并探讨了地质意义。5件辉钼矿样品的Re-Os模式年龄介于(158.8±2.2)Ma~(161.5±2.2)Ma之间,其加权平均值为(159.8±1.0)Ma(MSWD=0.92),等时线年龄为(161.7±3.1)Ma(MSWD=1.40)。红娘山杂岩体LA-ICP-MS锆石U-Pb年龄分别为:中粗粒花岗岩结晶年龄为(173±1)Ma(MSWD=0.88),似斑状花岗岩侵位年龄为(162±1)Ma(MSWD=0.40),石英斑岩结晶年龄为(160±2)Ma(MSWD=1.90)。辉钼矿Re-Os和锆石U-Pb定年结果表明,泉子沟钼矿床形成于晚侏罗世早期,成矿与似斑状花岗岩关系密切。泉子沟钼矿床的辉钼矿w(Re)介于16.49×10~(-6)~32.87×10~(-6),暗示成矿物质主要来自下地壳。     

西藏班公湖-怒江缝合带西段中特提斯洋盆的双向俯冲:来自岛弧型花岗岩锆石U-Pb年龄和元素地球化学的证据

笔者调查发现西藏班公湖-怒江缝合带西段狮泉河-改则-洞错蛇绿岩带北侧和拉果错蛇绿岩带南侧都有岛弧型花岗岩岩基产出。这些岩体岩性上以中粒花岗闪长岩为主,岩石化学上明显富集大离子不相容元素(LILE) Rb、Th、U、K、Pb,亏损高场强元素(HFSE)Nb、Ta、Ti,具有岛弧型岩浆岩的本质特征,指示着班公湖中特提斯洋盆存在双向俯冲。锆石U-Pb LAICPMS定年结果显示岩体在不同构造位置年龄并不一致,位于狮泉河-改则-洞错蛇绿岩带北侧的嘎拉勒和改则北两个岩体锆石²⁰⁶Pb/²³⁸U加权平均年龄分别为155.6±1.1Ma(MSWD=1.7)和142.15±0.35Ma(MSWD=2.9),位于拉果错蛇绿岩带南侧的扎布耶北岩体的锆石²⁰⁶Pb/²³⁸U加权平均年龄为134.07±0.77Ma(MSWD=1.8),表明班公湖中特提斯洋盆向北俯冲发生在晚侏罗世,而向南的俯冲发生在早白垩世,两者相差约8Ma。岛弧花岗岩浆都是由地幔楔部分熔融而成,岩浆源区经历过来自俯冲板片的沉积物熔体的交代。不同岩体的源区沉积物熔体的交代比例不同:扎布耶北岩体最多,大体在12%~16%之间;嘎拉勒岩体次之,在9%~13%之间;改则北岩体最少,为5%~10%。     

Geochronology of zircon megacrysts from nepheline-bearing gneisses as constraints on tectonic setting: implications for resetting of the U-Pb and Lu-Hf isotopic systems

Nepheline-bearing gneisses from the 75 km² Tambani body in the Mozambique Belt of southern Malawi, are miaskitic biotite-nepheline monzodiorites, reflecting an absence of K-feldspar, alkali amphiboles or pyroxenes, and contain euhedral zircon megacrysts up to 5 cm across. The zircons contain U = 1–1,860 ppm, Th = 0–2,170 ppm and Y = 400–1,100 ppm, and very low concentrations of all other measured trace elements except Hf (HfO₂ = 0.53–0.92 wt. %). Cathodoluminescence images reveal oscillatory sector growth zoning and no evidence for xenocrystic cores, indicating that the zircons represent primary magmatic crystallization products that have survived amphibolite grade metamorphism. U-Pb isotopic analyses (by TIMS) yield an upper intercept age of 730 ± 4 Ma (MSWD = 1.7), which we interpret as the time of magmatic crystallization of the zircons. This is coincident with 11 SHRIMP spot analyses, which yield a mean age of 729 ± 7 Ma (MSWD = 0.37). Metamorphism, at 522 ± 17 Ma as suggested by monazite, caused partial Pb-loss during local recrystallization of zircon. Lu-Hf isotopic data for three whole-rock samples of nepheline-bearing gneiss are collinear with those for zircon megacrysts, and correspond to an age of 584 ± 17 Ma (MSWD = 0.37. We interpret the Lu-Hf array to represent a mixing line defined by the Hf isotopic signature of primary zircon and that of the rock-forming minerals reset during metamorphic (re-)crystallization; hence the 584 Ma age is likely geologically meaningless. Given the well-defined association of nepheline syenites (and phonolitic volcanic equivalents) with continental rifting, we suggest that the Tambani body represents a magmatic product formed at 730 Ma during the break-up of the Rodinia supercontinent. The 522 Ma age is akin to other Pan-African metamorphic ages that record collisional suturing events during the final assembly of Gondwana. Zircon-bearing nepheline gneisses thus preserve a record of intra-continental rifting and of continental collision in southern Malawi.     

Timing of the Yuchiling giant porphyry Mo system, and implications for ore genesis

The Yuchiling Mo deposit is a recently discovered giant porphyry system in the East Qinling Mo belt, China. Its apparent causative intrusion, i.e., the Yuchiling granite porphyry, is the youngest intrusion (phase 4) of the Heyu multiphase granite batholith, which was emplaced between 143 and 135 Ma. New robust constraints on the formation of the Yuchiling porphyry Mo system are provided by combined zircon U–Pb, biotite ⁴⁰Ar/³⁹Ar, and molybdenite Re–Os dating. Zircon grains from the Mo-mineralized granite porphyry yield weighted ²⁰⁶Pb/²³⁸U age of 134.0?±?1.4 Ma (n?=?19, 2σ error, MSWD?=?0.30). Magmatic biotite from the same sample yield a ⁴⁰Ar/³⁹Ar plateau age of 135.1?±?1.4 Ma (2σ error), and an inverse isochron age of 135.6?±?2.0 Ma (n?=?7, 2σ error, MSWD?=?10.8), which are effectively coincident with the zircon U–Pb age within analytical error. Three pulses of mineralization can be deduced from the molybdenite Re–Os ages, namely: ～141, ～137, and ～134 Ma, which agree well with the zircon U–Pb ages of granitic phases 1, 2, and the Yuchiling porphyry (phase 4), respectively. These well-constrained temporal correlations indicate that Mo mineralization was caused by pulses of granitic magmatism, and that the ore-forming magmatic-hydrothermal activity responsible for the Yuchiling porphyry Mo system lasted about 8 Ma. The Yuchiling Mo deposit represents a unique style of porphyry Mo system formed in a post-collision setting, and associated with F-rich, high-K calc-alkaline intrusions, which differ from convergent margin-associated porphyry Mo deposits.     

Geochronology of the Dovyren intrusive complex, northwestern Baikal area, Russia, in the Neoproterozoic

The paper reports newly obtained data on the geochronology of the Dovyren intrusive complex and associated metarhyolites of the Inyaptuk Formation in the Synnyr Range. The data were obtained by local LA-ICPMS analysis of zircons in samples. The U-Pb age of olivine-free gabbronorite from near the roof of the Yoko-Dovyren Massif is 730 ± 6 Ma (MSWD = 1.7, n = 33, three samples) is close to the estimated age of 731 ± 4 Ma (MSWD = 1.3, n = 56, five samples) of a 200-m-thick sill beneath the pluton. These data overlap the age of recrystallized hornfels found within the massif (“charnockitoid”, 723 ± 7 Ma, MSWD = 0.12, n = 10) and a dike of sulfidated gabbronorite below the bottom of the massif (725 ± 8 Ma, MSWD = 2.0, n = 15). The estimates are also consistent with the age of albite hornfels (721 ± 6 Ma, MSWD = 0.78, n = 12), which was produced in a low-temperature contact metamorphic facies of the host rocks. The average age of the Dovyren Complex is 728.4 ± 3.4 Ma (MSWD = 1.8, n = 99) based on data on the sill, near-roof gabbronorite, and “charnockitoid”) and is roughly 55 Ma older than the estimate of 673 ± 22 Ma (Sm-Nd; [13]). The U-Pb system of zircon in two quartz metaporphyre samples from the bottom portion of the Inyaptuk volcanic formation in the northeastern part of the Yoko-Dovyren Massif turns out to be disturbed. The scatter of the data points can be explained by the effect of two discrete events. The age of the first zircon population is then 729 ± 14 Ma (MSWD = 0.74, n = 8), and that of the second population is 667 ± 14 Ma (MSWD = 1.9, n = 13). The older value pertains to intrusive rocks of Dovyren, and the age of the “rejuvenated” zircon grains corresponds to the hydrothermal-metasomatic processes, which affected the whole volcano-plutonic sequence and involved the serpentinization of the hyperbasites. This is validated by the results of Rb-Sr isotopic studies with the partial acid leaching of two serpentinized peridotite samples from the Verblyud Sill. These studies date the overprinted processes at 659 ± 5 Ma (MSWD = 1.3, n = 3).     

中国东北完达山地区早白垩世同构造岩浆侵位——对晚中生代左行走滑作用的响应

分布于中国东北完达山地区的饶河花岗岩岩体中暗色矿物和斑晶钾长石定向排列,呈北北东走向,其中透镜状闪长质捕掳体近水平排列,局部具有左行剪切的特点。岩体中发育石香肠状石英脉,表明岩体在侵位过程中受到左行剪切作用的影响或制约。对出露的花岗岩进行LA-ICP-MS锆石U-Pb定年,获得年龄121±1Ma和119±1Ma,表明该岩浆流动形成于早白垩世。同时对围岩辉长岩、侵入岩体中的正长岩脉和辉绿岩脉进行锆石U-Pb年龄分析,分别获得160±1Ma、109±2Ma、124±1Ma的年龄结果。根据各样品中继承锆石的特征,围岩辉长岩的年龄数据很集中,不存在古老锆石的年龄信息。岩浆流动岩体及岩脉中都有太古宙、元古宙等各时代的锆石年龄数据,可能表明完达山地区在约120Ma之前已完成古太平洋板块的俯冲拼贴,饶河岩体形成于走滑环境下的陆内变形,为同构造侵入岩。     

The age of camptonite dikes of the Agardag alkali-basalt complex (western Sangilen): results of Ar/Ar and U/Pb dating

A camptonite dike swarm (Agardag alkali-basalt complex) in the western part of the Sangilen Upland abounds in mantle xenoliths. Mineralogical, petrographic, and petrochemical studies show that the dikes are composed of lamprophyres of two groups, basic and ultrabasic. Ar/Ar dating of amphibole and phlogopite megacrysts gives an intrusion age for the dikes of 443.0 ± 1.3 Ma. ²⁰⁶Pb/²³⁸U dating of zircon from a glomeroporphyritic intergrowth in camptonite from one of the dikes yielded a core age of 489.0 ± 5.4 Ma. This corresponds to the time of formation of the Chzhargalanta granite–leucogranite complex (489.4 ± 2.6 Ma). The ²⁰⁶Pb/²³⁸U age of the zircon rim is 444.0 ± 7.5 Ma. The ages obtained by Ar/Ar dating of amphibole and biotite megacrysts and by U/Pb dating of the magmatic rim of zircon crystal from the camptonite coincide within the dating error, which indicates that the camptonite dikes formed in the Late Ordovician. These dikes are the oldest-known example of mantle-derived xenoliths in mafic volcanic rocks from an off-craton setting. These are samples of the Upper Ordovician lithospheric mantle.     

湘南尖峰岭岩体锆石U-Pb年龄、地球化学特征及成因

香花岭锡多金属矿田处于南岭西段中_晚侏罗世形成的花山_西山_香花岭_骑田岭NE向的富碱侵入岩带上,是湘南地区矿化类型最为完整的锡矿区。尖峰岭岩体为矿田内主要的成矿母岩之一。为了进一步明确尖峰岭黑云母花岗岩的岩石成因及成岩年龄,笔者对尖峰岭黑云母花岗岩开展了LA_ICP_MS锆石U_Pb测年及岩石地球化学特征分析。锆石LA_ICP_MS U_Pb测年获得206Pb/238U年龄介于(158.6±2.3)Ma~(164.8±4.5)Ma之间,加权平均年龄为(160.7±2.2)Ma(MSWD=0.8),这与香花岭锡多金属矿田的成矿时限(154~161 Ma)相吻合,表明岩体的侵位与区内多金属成矿作用均发生于中_晚侏罗世。尖峰岭岩体的主量、微量元素研究显示,尖峰岭黑云母花岗岩具有富硅、富碱及成矿元素,富LILE及Zr、Ga等部分高场强元素(HFSE),贫Ca、Mg、P、Eu特征,指示尖峰岭黑云母花岗岩属于过铝质A型花岗岩(A2型)。综合研究表明,尖峰岭黑云母花岗岩体与其周缘钨锡多金属矿床在时间、空间及成因上有密切关系。结合区域上已有的同位素年代学数据,香花岭矿区的成岩成矿作用与南岭西段同时代的其他钨锡多金属矿床形成于同一岩石圈伸展的地球动力学背景下。     

陕西洛南县石家湾钼矿Re-Os同位素年龄及地质意义

陕西石家湾钼矿床位于东秦岭成矿带西段黄龙铺地区,钼矿化呈细脉-网脉状分布于花岗斑岩体及其围岩中,与矿化有关的围岩蚀变有钾长石化、硅化、绢云母化,属斑岩型矿床.在矿床中选取不同矿化类型的辉钼矿样品,进行了Re～Os同位素定年,获得模式年龄变化范围为143.1±2.1～145.1±2.2 Ma之间,其加权平均年龄(144.0±1.1 Ma,MSWD=0.91)、等时线年龄(145.4±2.1 Ma,MSWD=0.83)与石家湾斑岩体的成岩年龄(141.4±0.6Ma)相近,说明成岩成矿作用发生在晚侏罗世一早白垩世.综合辉钼矿中Re的含量、硫同位素以及相关岩体的源区特征等多方面证据认为,石家湾斑岩型钼矿的成矿物质主要来自于下地壳,并混有少量幔源成分.     

西藏冈底斯南部陆陆碰撞早期成矿作用分析

冈底斯带南部发育有大量的斑岩铜钼矿床和矽卡岩型铜铅锌多金属矿床,形成了斑岩铜矿带和多金属矿带.前人的研究表明,成矿带内的矿床形成年代大都小于30Ma,处于碰撞后期伸展构造环境.本文对冈底斯带中南部的甲龙矽卡岩型铁矿、撒当金银矿床(点)和多底沟矽卡岩型钼矿床(点)开展了年代学研究,结果显示:甲龙铁矿黑云母二长花岗斑岩的锆石LA-ICP-MS U-Pb年龄为61.1 ±0.4Ma,MSWD=0.94;撒当赋矿安山岩锆石LA-ICP-MS U-Pb年龄为62.6±0.5Ma,MSWD=1.51;多底沟钼矿床(点)3件辉钼矿Re-Os模式年龄为64.3±0.8Ma ～ 69.2±3.3Ma,加权平均模式年龄为66.7±6.4Ma(MSWD=8.1).三个矿床(点)的同位素年龄表明成岩成矿事件和印度-欧亚板块陆陆碰撞早期构造岩浆事件有关.结合前人工作,我们提出冈底斯中南部发生了大规模与陆陆碰撞早期岩浆事件有关的成矿作用,形成了大面积分布的矿床,具有良好的找矿前景,应引起更多关注.     

西藏曲水县达布斑岩铜(钼)矿床成岩成矿年代学研究

本文采用锆石LA-ICP-MS微区U-Pb测年技术,对冈底斯成矿带东段曲水县达布斑岩Cu(Mo)矿床北部达布矿区含矿斑岩体、南部显角囊含矿花岗闪长斑岩岩体进行了年代学研究,通过对3件岩体样品中单颗粒锆石的分析,达布主矿体花岗闪长斑岩样品206Pb/238U年龄加权平均值为16.5±0.05Ma(n=15,MSWD=3),达布主含矿体二长花岗斑岩样品年龄为16.1±0.13Ma(n=15,MSWD=1.03),南部显角囊矿体花岗闪长斑岩年龄为16.2±0.04Ma(n=13,MSWD=0.0064)。对达布矿床斑岩Cu(Mo)矿床主矿体中4件辉钼矿样品,显角囊矿体中6件辉钼矿样品,分别进行了Re-Os同位素测试,等时线年龄分别为14.6±0.50Ma(MSWD=0.35,主矿体)、14.8±0.23Ma(MSWD=1.3,显角囊)。结合前人研究以及本次测年结果认为:1)达布斑岩铜(钼)矿床岩体侵位的年龄应限定在16Ma左右,成矿时代为14Ma左右,成矿时间差小于0.86Ma,与区域上"成矿瞬时发生"的成矿规律是一致的;2)矿床产出于印度-亚洲大陆板块后碰撞伸展环境。     

新疆阿尔泰南缘大东沟铅锌矿区火山岩LA-ICP-MS锆石U-Pb定年及地质意义

大东沟铅锌矿位于新疆阿尔泰南缘的克兰盆地,赋存于康布铁堡组上亚组火山-沉积岩系,矿体直接围岩为变质钙质砂岩及不纯的大理岩,矿体呈层状、似层状、透镜状分布,与地层产状一致。利用LA-ICP-MS锆石U-Pb测年法,获得矿区2件康布铁堡组上亚组变质流纹岩加权平均年龄分别为(388.9±3.2)Ma(MSWD=3.3)和(400.7±1.6)Ma(MSWD=1.3)。结合前人的年龄数据,将克兰盆地康布铁堡组的时代厘定为晚志留世末期至早泥盆世(413~389 Ma)。大东沟铅锌矿为火山岩容矿的喷流沉积型矿床(VMS),2件变质流纹岩年龄限定大东沟铅锌矿的成矿作用发生在早泥盆世(401~389 Ma)。     

福建省紫金山铜金矿田石帽山群下组火山岩锆石LA-ICP-MS U-Pb测年与白垩纪岩浆活动期次

通过对石帽山群下组底部火山岩两组原位锆石进行LA-ICP-MSU-Pb测年,准确厘定了福建省紫金山铜金矿田中石帽山群下组火山岩的时代,获得206Pb/238U加权平均年龄分别为113.0±1.9Ma(n=16,MSWD=1.02)和110.1±0.7Ma(n=16,MSWD=0.16),并取得了131.8～162.7Ma和501.3Ma的捕获锆石或继承锆石的年龄信息。结合近年前人发表的锆石测年成果,将紫金山铜金矿田白垩纪岩浆活动划分为三个阶段:(1)115～110Ma为早期火山爆发-溢流阶段;(2)110～105Ma为中期岩浆溢流-隐爆-填塞火山通道及四坊岩体侵位阶段;(3)105～95Ma为晚期多阶段花岗闪长斑岩侵位与斑岩-热液成矿作用阶段。这为紫金山铜金矿田白垩纪岩浆活动期次与成矿时代研究提供了重要新资料。