共查询到20条相似文献，搜索用时 46 毫秒
1.
紫金山矿田位于华南褶皱系东部,闽西南凹陷西南部,是我国大型-超大型浅成低温热液铜金矿床,区内发现多个与岩浆活动密切相关的金、银、铜等金属矿床.对紫金山矿田东南矿段与成矿密切相关的细粒黑云母花岗岩开展了详细野外地质调查、岩相学和锆石稀土元素、U-Pb年代学和Hf同位素研究.LA-ICP-MS法获得细粒黑云母花岗岩中岩浆结晶锆石206Pb/238U-207Pb/235U谐和年龄为109.5±1.9 Ma（MSWD=0.74,N=16）,206Pb/238U加权平均年龄为107.44±0.94 Ma（MSWD=1.06,N=16）,二者在误差范围内结果一致,结合锆石稀土元素和岩浆振荡环带特征及Th/U比值,上述年龄结果可代表岩石的结晶年龄,表明细粒黑云母花岗岩侵位于燕山期早白垩世.细粒黑云母花岗岩锆石Hf同位素初始比值εHf（t）均为负,介于-4.99~-1.06（平均值为-2.99）;两阶段Hf模式年龄（tDM2）介于1 233.7~1 485.4 Ma（平均值为1 362.4 Ma）.样品的εHf（t）、Hf同位素地壳模式年龄分布范围变化较小,暗示岩体的岩浆来源具有较为均一的锆石Hf同位素组成.紫金山矿田东南矿段早白垩世花岗岩体的锆石U-Pb年龄和Hf同位素特征,反映了闽西南早白垩世的岩浆成矿活动时间和源区特征,其成因与中国东南部岩石圈伸展减薄和壳源物质参与岩浆形成演化密切相关. 相似文献
2.
3.
新疆东准噶尔老鸦泉岩体的锆石U-Pb年龄和地球化学组成 总被引：5，自引：0，他引：5
老鸦泉岩体是贝勒库都克锡矿带内最大的花岗岩体,它主要由黑云母钾长花岗岩组成。通过对2件样品的锆石LA-ICP-MS U-Pb同位素年龄测定,获得其206Pb/238U年龄值分别为301±2 Ma和300±5 Ma,指示该岩体侵位时代为晚石炭世。岩石地球化学组成表明,老鸦泉碱长花岗岩具有富硅、富碱,相对富集Rb、K、Th、U、Nd、Hf等元素,而贫Ba、Sr、P、Ti等元素,具强负Eu异常,总体显示A型花岗岩的地球化学特征。锆石U-Pb年龄及岩石地球化学特征都表明老鸦泉岩体的形成与晚石炭世北疆强烈的后碰撞岩浆活动有着密切关系。 相似文献
4.
骨头崖花岗岩位于北秦岭构造带东部,西峡县北部,对其开展岩石成因研究有助于深入认识燕山期北秦岭豫西南段深部构造演化。岩体定年样品(GTY01)为中粒斑状黑云母二长花岗岩,30个锆石测点中有25个测点的U-Pb同位素测定值位于或者接近~(207)Pb/~(235)U–~(206)Pb/~(238)U一致线,23个测点的~(206)Pb/~(238)U年龄介于108.4±0.9Ma~114.3±1.0Ma之间,其加权平均年龄为111.7±0.6Ma(MSWD=1.4),代表了骨头崖花岗岩的形成时代。锆石稀土元素具有轻稀土亏损、重稀土富集、Ce正异常及负Eu异常的特征,形成温度介于626℃~769℃之间,岩体的锆石/熔体中重稀土元素特征表明,其形成过程中经历了岩浆混合作用。骨头崖花岗岩为富硅、碱和贫钙、镁的高钾钙碱性系列。岩体富集Rb、Th和亏损Nb、Ta、Ti。岩体的稀土配分模式具有右倾、轻稀土富集、重稀土亏损和负Eu异常的特征,(Eu值介于0.48~0.60之间,(La/Yb)_N范围为5.82~11.19,源区组成和部分熔融程度控制了骨头崖花岗岩的成分变异。骨头崖花岗岩形成于厚度为~40km的地壳内,其部分熔融源区为角闪岩相,部分熔融残余相主要为角闪石和斜长石。骨头崖花岗岩是岩石圈拆沉作用所触发的岩浆底侵作用的产物,从源区岩石部分熔融到最终上侵固结成岩耗时~15Ma,它是岩石圈拆沉作用滞后的岩浆响应。 相似文献
5.
对蒙古国南戈壁省东部的西南欧玉岩体黑云母花岗岩锆石进行了阴极发光照相,结果显示,其具有明显的振荡环带,为典型的岩浆锆石特征。对22颗锆石进行了LA-MC-ICP-MS U-Pb年龄测定,结果显示,21个测点的~(206)Pb/~(238)U年龄介于334±2~335±2Ma之间,年龄加权平均值为335±1Ma,表明西南欧玉岩体形成于早石炭世。 相似文献
6.
冀南西石门矽卡岩型铁矿床成矿年代:热液锆石U-Pb年龄的证据 总被引：1，自引：0，他引：1
西石门铁矿床是华北地区最为典型的矽卡岩型铁矿床之一,最新获得金云母40 Ar-39 Ar成矿年龄为(133.1±1.3)Ma、(137.1±1.5)Ma,略老于其成矿母岩(武安杂岩体)形成的年龄(126~136 Ma),这是矛盾的。笔者对角闪正长岩和矽卡岩脉中的锆石进行了LA-ICP-MS U-Pb同位素年代学分析。结果表明,角闪正长岩中锆石呈浅黄色-无色、透明、棱角状、不规则状,振荡环带结构不发育,部分锆石中含棱角状继承锆石内核,206 Pb-238 U年龄加权平均值为(135.6±1.5)Ma,代表了武安杂岩体的结晶年龄。矽卡岩脉中锆石呈棕色,含有少量细小的包裹体,呈透明-半透明,相对于岩浆锆石具有低的Th、U、REE含量及Th/U值(Th=(222.37~1541.11)×10-6,U=(218.44~989.17)×10-6,Th/U=0.90~1.56),并具有强烈的Ce正异常(δCe=4.46~196.22)和Eu负异常(δEu=0.59~0.80),206Pb-238 U年龄介于124.9~133.0Ma,加权平均值为(129.4±2.6)Ma,代表了热液锆石的形成年龄,说明129 Ma是该西石门地区主要成矿期。 相似文献
7.
海南尖峰岭岩体热液锆石U-Pb定年及微量元素研究: 对热液作用及抱伦金矿成矿时代的限定 总被引：4，自引：0，他引：4
海南抱伦金矿矿区尖峰岭岩体中的锆石可分为岩浆锆石和热液锆石.岩浆锆石无色、透明, 长柱状、无明显包裹体, U、Th含量多小于1000μg/g, 206Pb-238U年龄加权平均值为240±2.1Ma, 代表了尖峰岭岩体的结晶年龄.热液锆石呈褐色、浑浊、半透明的自形短柱状, 相对于岩浆锆石具有异常高的U、Th及微量元素含量, 其U含量最高可达30000μg/g, Th含量最高可达20000μg/g, 微量及稀土元素含量比岩浆锆石普遍高一个数量级, 且具有较高的普通Pb.LA-ICP-MS锆石U-Pb定年结果表明, 这些热液锆石的形成年龄为106~120Ma之间, 206Pb-238U年龄加权平均值为112.8±4.3Ma, 代表了热液作用的年龄, 显示该区在112~120Ma左右经历了一次强烈的热液作用, 可能与该区燕山期大规模的岩浆作用以及抱伦金矿的成矿有关.研究还表明, 对热液锆石直接进行微区原位U-Pb定年, 可用来准确测定热液作用的时间和限定热液成因金矿床的成矿时代. 相似文献
8.
9.
阿尔金南缘清水泉地区与基性-超基性岩伴生的花岗岩为斜长花岗岩。岩石地球化学显示该花岗岩高硅、富铝和钠,低镁和钾;轻稀土富集,具有Eu的正异常(δEu为1.01~2.01)。岩石富Rb、Ba,特别高Sr(779×10-6~864×10-6),低Y(1.17×10-6~1.51×10-6)及Yb(0.15×10-6~0.20×10-6),强烈亏损Nb、Ta等。斜长花岗岩锆石振荡环带清晰,Th/U和Nb/Ta比值分别为0.38~0.52,2.92~5.04;具有明显的Ce正异常和Eu负异常,为典型的岩浆锆石,利用LA-ICP-MS微区原位定年获得该花岗岩206Pb/238U-207Pb/235U谐和年龄为465Ma,206Pb/238U加权平均年龄为451±4Ma。锆石饱和温度计和锆石Ti温度计演算结果显示锆石的结晶温度分别为783~811℃和693~821℃。推测花岗岩源区压力范围为1.8~2.0GPa,形成深度在60km以上。综合分析清水泉花岗岩主、微量元素地球化学特征,并结合区域地质,认为该花岗岩属"I"型花岗岩,由地幔基性岩浆上侵分异形成,产于伸展环境。 相似文献
10.
《吉林地质》2016,(3)
内蒙古鄂温克旗头道桥地区的大牛圈—乌其哈锡岩体主要由二长花岗岩组成,石英二长闪长岩、花岗闪长岩、花岗岩在岩体中零星出露,石英二长闪长岩锆石的~(206)Pb/~(238)U年龄的加权平均值为(285±6)Ma;二长花岗岩锆石的~(206)Pb/~(238)U年龄的加权平均值分别为(259±11)Ma、(292±6)Ma、(288.3±2.9)Ma;花岗岩锆石的~(206)Pb/~(238)U年龄的加权平均值为(303±8)Ma。根据上述年龄分布情况及该岩体岩石学、岩石化学及地球化学均表现出同源、同期的产物特征,故认为该岩体的结晶年龄为(285±6)Ma。结合区域构造背景分析大牛圈—乌其哈锡地区造山晚期花岗岩体应该是兴安微板块与松嫩微板块碰撞拼合晚期阶段的产物,故两微板块的拼合时间发生在至少285 Ma以前。 相似文献
11.
12.
河北矾山杂岩体中单斜辉石的研究 总被引：3，自引：1，他引：2
河北矾山杂岩体属于二氧化硅不饱和的超钾质碱性-过碱性岩浆系列,由单斜辉石岩、辉石正长岩和碱长正长岩等不同类型岩石组成。各类型岩石主要组成矿物为单斜辉石、黑云母、石榴石和正长石。本文利用电子探针对单斜辉石进行了详细研究,发现所有单斜辉石属于高钙透辉石,随着岩浆的演化,主要表现为Fe2+对Mg2+的替代关系,结晶趋势为透辉石→钙铁辉石,这揭示矾山杂岩体岩浆体系的特点是高温、中等大小的氧逸度、贫硅、富碱（尤其是钾）。辉石中的AlIV含量取决于岩浆的硅饱和度,硅越不饱和,AlIV含量越高;AlVI含量则与体系中的Al含量呈正相关关系。由Al对Si的替代引起的电荷不平衡主要由八面体位置的Fe3+来补偿,其次为少量的Ti4+和更少量的Al3+。体系中的Ti含量与体系的温度呈正相关关系,而Na含量则与辉石中的Ti和Fe3+含量成正相关关系。不同类型岩石中单斜辉石从核部到边部随着Mg#的降低,Al、Ti含量呈现不同的演化趋势,这是因为它们于岩浆演化的不同阶段开始结晶,经历了不同的岩浆演化史。碱性岩中高钙辉石的出现和成分环带的普遍发育是由岩浆的贫硅富钾特征决定的。单斜辉石的成分不仅受控于结晶时的温度、压力条件,也受控于岩浆的总成分及其变异。 相似文献
13.
Roger Bateman 《Australian Journal of Earth Sciences》2013,60(3-4):253-265
The Bruinbun pluton is a small, massive, I‐type granitoid intruded into the meta‐sedimentary Hill End Trough, in eastern N.S.W. It is a multiple pluton representing two discrete magma pulses, the granodiorite core intruding the adamellite margin. A weak alignment of orthoclase megacrysts in the granitoids is best developed adjacent to both the internal and external intrusive contacts, and is considered by the writer to be a product of magmatic flow. Part of the northern contact and the southern and western contacts dip inward at moderate angles, whereas the eastern contact is vertical to outward‐dipping. The pluton is inferred to be mushroom‐shaped, and slightly tilted. The intensity of aureole deformation is low. The aureole has been flexed into concordancy with the pluton roof, and a rudimentary rim fold‐zone is present around lower levels of the pluton. Intrusion of the granitoid is inferred to be primarily by uplift of its roof and depression of its floor. The highest‐grade contact metamorphic parageneses developed are: cordierite‐K feldspar‐biotite‐quartzite ± andesine ± epidote in metapelites, and ferrohornblende‐biotite‐muscovite‐andesine‐epidote‐quartz in metavolcarenites. No intrusion‐related foliation or lineation was formed. 相似文献
14.
Burpala is a unique peralkaline pluton known to the world. Alkaline pegmatites of the pluton contain about 70 rare-metal minerals.
A new scheme of rock crystallization is offered: shonkinite → nepheline syenite → alkali syenite → quartz syenite → vein rocks:
mariupolite, rare-metal pegmatite, apatite-fluorite, and alkali granite. Investigation of fluid inclusions in fluorite from
the apatite-fluorite rocks established the high temperatures (520–560°C) of homogenization of multiphase salt inclusions.
Fluids from inclusions are dominated by hydrocarbonates and chlorides as anions and sodium and calcium as cations; microelements
include strontium, barium, boron, iron, manganese, lithium, rubidium, and cesium, i.e., components characteristic of magmatogenic
fluids. These rocks are analogous to foskorites of carbonatite complexes in the high calcium content, but calcite is replaced
with fluorite along with other foskorite minerals such as apatite, magnetite, mica, and pyroxene. 相似文献
15.
We present centrifuge experiments to study the surface deformation induced by shallow pluton emplacement in a rheologically stratified crust. Sand simulates the topmost brittle crust; plastilina and denser silicone represent more and less competent crustal portions, respectively; lighter silicone simulates a buoyant intrusion. In the models, density differences affect the rate of intrusion but not their evolution or shape, whereas viscosity and strength stratifications control both the shape and rate of the intrusions. With a higher viscosity contrast (102–4) between the intrusion and the embedding media, the rise of the lighter silicone induces a laccolith-like intrusion, responsible for doming and thinning of the overburden; an apical depression may form, inducing silicone extrusion. Conversely, with a lower (101) viscosity contrast, the overburden and the intrusion exhibit a lens-shaped form, with a broad central depression bordered by an upward flexure towards the periphery. A sag in the floor of the intrusion is commonly observed; no silicone extrusion occurred. The intrusion is a hybrid between a laccolith and a lopolith. The comparison with nature (1) confirms roof uplift as an important means of accommodating space during pluton emplacement and (2) suggests that, where roof uplift plays a major role, pluton emplacement can induce a well-correlated sequence of events at surface: doming, the development of a depression and extrusion. 相似文献
16.
《Journal of Structural Geology》1999,21(8-9):1109-1117
The Late Cretaceous Mono Creek granite has a pronounced NW–SE elongate shape, 60 km long by 10 km wide, characteristic of plutons from the eastern Sierra Nevada batholith. An 8 km-wide bulge exists on the NE side of this pluton, which exhibits evidence of forceful emplacement (or in-situ ballooning), such as deflection of metamorphic wallrock and igneous foliation, and the orientation of fracture patterns. Three-dimensional strain analysis indicates that wallrock strains do not provide enough volume to accommodate the emplacement of the bulge, a recurring problem in studies of plutonic terranes.We suggest that emplacement of the Mono Creek bulge was accommodated by all components of the three-dimensional displacement field—including translation, rotation, and pure strain (shape change)—of the surrounding units. Classical strain analysis only addresses the rotation and pure strain components, and is incapable of quantifying the translation component. However, our analysis suggests that translation plays the dominant role in the emplacement process. A shell model of translation of the surrounding igneous and metamorphic units is proposed for the Mono Creek bulge, which suggests that the translation component decreases dramatically away from the intrusion, consistent with the observed geology and finite strain analysis. We propose that translation is the solution to the recurring pluton `space' problem, either through tectonically controlled (passive) or magmatically controlled (active) movement of the wallrocks. Translation is generally the neglected component of the displacement field, but it may often be evaluated through judicious use of finite strain analysis and tectonic reconstruction. 相似文献
17.
V. N. Yakovenchuk G. Yu. Ivanyuk Ya. A. Pakhomovsky Yu. P. Men’shikov N. G. Konopleva Yu. A. Korchak 《Geology of Ore Deposits》2008,50(8):732-745
Seven pyroxene varieties were identified in nepheline syenites and foidolites of the Khibiny pluton: enstatite, ferrosilite, diopside, hedenbergite, augite, aegirine-augite, and aegirine. Enstatite and augite are typical of alkaline and ultramafic rocks of dike series. Ferrosilite was found in country quartzitic hornfels. Diopside is a rock-forming mineral in alkaline and ultramafic rocks, alkali gabbroids, hornfels in xenoliths of volcanic and sedimentary rocks and foyaite, melteigite-urtite that assimilate them, and certain hydrothermal pegmatite veins. Hedenbergite was noted in hornfels from xenoliths of volcanic and sedimentary rocks and in a hydrothermal pegmatite vein at Mount Eveslogchorr. Aegirine-augite is the predominant pyroxene in all types of nepheline syenites, phonolites and tinguaites, foidolites, alkaline and ultramafic rocks of dike series, fenitized wall rocks surrounding the pluton, and xenoliths of Devonian volcanic and sedimentary rocks. Aegirine is an abundant primary or, more often, secondary mineral in nepheline syenites, foidolites, and hydrothermal pegmatite veins. It occurs as separate crystals, outer zones of diopside and aegirine-augite crystals, and homoaxial pseudomorphs after Na-Ca amphiboles. Microprobe analyses of 265 pyroxenes samples allowed us to distinguish ten principal trends of isomorphic replacement and corresponding typomorphic features of pyroxenes. Compositional variations in clinopyroxenes along the sampled 35-km profile from the margin of the Khibiny pluton to its center confirm the symmetric zoning of the foyaite pluton relative to semicircular faults of the Minor Arc and the Main (Central) Ring marked by Devonian volcanic and sedimentary rocks, foidolites, and related metasomatic rocks (rischorrite, albitite, and aegirinite). Changes in the composition of pyroxenes are explained mainly by the redistribution of elements between coexisting minerals of foyaites in the process of their intense differentiation under the effect of foidolite melts that have intruded into the circular fault zones. 相似文献
18.
红格岩体的围岩及其时代 总被引：2，自引：1，他引：2
<正> 一、红格岩体围岩概述 红格含钒钛磁铁矿基—超基性岩体(以下简称含矿岩体)位于四川省渡口市东北郊。其围岩北延入米易县,西南延部分构成渡口市内攀枝花含矿岩体的围岩。在红格岩体的勘探过程中,四川省地质矿产局攀西地质八队对其围岩作了不少工作,在这个南北向断裂较为发育的地区发现了若干条岩层出露较好且相对连续的剖面,建立了相应的群、组名称。在此基础上,笔者重新观察了这些剖面并作了室内研究,按地层规范对群、组名称作了若干修正,与会理南部和云南元谋的有关地层进行了对比。该岩体的围岩,明显由两大套地层组成(图1),概述如下。 相似文献
19.
喜马拉雅造山带晚中新世麻迦淡色花岗岩的构建机制 总被引：3，自引：0，他引：3
在北喜马拉雅萨迦片麻岩穹窿西南侧发育有麻迦淡色花岗岩体,出露于南北向申扎—定结裂谷正断层的下盘,属一处较大规模的晚中新世淡色花岗岩体。该岩体具有较均一的元素和同位素(Sr和Nd)组成,但与多数喜马拉雅淡色花岗岩相比,具有异常高的(~(87)Sr/~(86)Sr)_i比值(0.85033~0.85034)和异常低的_(εNd)(t)值(-19.26~-18.30)组成,指示其部分熔融源区有更成熟古老地壳物质的参与。麻迦淡色花岗岩SHRIMP锆石U-Pb定年结果显示:1该岩体主要记录了至少两阶段岩浆结晶作用,分别发生在11.6±0.2 Ma和9.6±0.2 Ma;2个别13.8~16.0 Ma的岩浆作用年龄;3多数锆石继承核年龄分布于泛非期,少数年龄为中元古代(1558~1584 Ma)。在麻迦淡色花岗岩体南侧约40km处的日玛那穹窿,同位于申扎—定结南北向正断层的下盘,出露有大量原岩年龄为古元古代的日玛那糜棱岩,元素地球化学特征上类似于变泥质岩,显示高SiO_2(70.6%~74.6%),Al_2O_3(12.3%~14.0%),K_2O(4.22%~4.93%),A/CNK(1.50~1.58)和K_2O/Na_2O(1.42~2.18),代表了部分熔融源区可能存在的古老地壳物质岩石单元。因此,以麻迦淡色花岗岩为代表的北喜马拉雅晚中新世地壳深熔作用可能与青藏高原后碰撞阶段东西向伸展作用相关,泛非期变泥质岩及少量日玛那糜棱岩所代表的更古老岩石单元在16.0 Ma开始发生部分熔融,并在11.6 Ma至9.6 Ma之间达到深熔作用峰期,熔体活动可能持续了~2myr,以岩脉汇聚的形式延南北向正断层上升,构成侵位至北喜马拉雅特提斯沉积岩系之中的晚中新世麻迦淡色花岗岩体。 相似文献
20.
大宁岩体由二长花岗岩、花岗闪长岩及石英二长闪长岩组成,侵入时代为晚志留世(K—A r法407、445M a)。通过对岩体的微量元素、稀土元素及硫、铅、氧等同位素研究,认为银、金矿的成矿物质来自深源岩浆,大量的暗色包体是主要的成矿物质之一,在深大断裂的切割影响下,经多次构造活动,使得不同阶段的成矿物质富集并叠加而形成矿体。最利于A u、A g成矿的部位是花岗闪长岩与石英二长闪长岩的接触界线附近以及花岗闪长岩与围岩接触带附近的断裂交汇处。 相似文献