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1.
清流玮埔地区花岗岩的时代和岩石序列   总被引:5,自引:0,他引:5  
清流玮埔岩体曾是福建省印支期代表性岩体之一,出露有一定规模,前人把它作为单一的具片麻状构造黑云母二长花岗岩,在1:5万嵩口坪等4幅侵入岩调查中,全面采用侵入岩岩石谱系调查的新理论和新方法,对该岩体进行详细解体,划分出41个侵入体,建立7个单元,将其归并为廖武坪序列,玮埔单元,盘兰溪序列,并确定了志留纪,三叠纪和晚侏罗纪3个时期的岩浆活动,在对该岩体的时代划分基础上,对不同时代岩石序列,岩石化学,地  相似文献   

2.
内蒙古呼鲁斯太地区早元古代花岗岩的地质特征及成因   总被引:3,自引:0,他引:3  
内蒙古阿拉善左旗呼鲁斯太地区出露的太古代贺兰山群变质岩中分布有大量早元古代花岗岩。过去将这些花岗岩一直认为是混合花岗岩,笔者通过1:5万区调研究认为这些花岗岩属于岩浆成因,并按花岗岩类岩石谱系单位划分方案建立7个单元,将其中5个单元并为两个超单元。本文通过岩体地质、岩石学、矿物学、岩石化学和地球化学等方面论述了花岗岩的成因,并进一步探讨了花岗岩的成因类型、岩浆起源和源岩物质成分等问题。  相似文献   

3.
作者在1:5万狮子坪幅的区域地质调查中,采用花岗岩类岩石谱系单位的划分原则与方法,对产出于秦岭群的灰池子复式岩体进行了解体。共计划分为约80个小侵入体,并建立了9个单元,由老而新依次归并为蔡家沟、淇河、明郎河等3个序列。对各个单元及序列的岩石类型、矿物成分、结构特点、互相接触关系等作了简要的描述。本区花岗岩总体上呈现出由云英闪长岩→花岗闪长岩→二长花岗岩的演化序列,表明岩浆岩具有多期次熔融与分异、侵位活动的规律性变化。  相似文献   

4.
东秦岭灰池子复式岩体岩石谱系单位划分及其地质意义   总被引:2,自引:2,他引:2  
作者在1:5万狮子坪幅的地区地质调查中,采用花岗岩类岩石谱系单位的划分原则与方法,对产出于秦岭群的灰池子复式岩体进行了解体。共计划分为约80个小侵入体,并建立了9个单元,由老而新依次归并为蔡家沟、淇河、明郎河等3个序列。对各个单元及序列的岩石类型、矿物成分、结构特点、互相接触关系等作了简要的描述。本区花岗岩总体上呈现出由云英闪长岩-花岗闪长岩-二长花岗岩的演化序列,表明岩浆岩具有多期次熔融与分异,  相似文献   

5.
北秦岭富水基性杂岩体岩石谱系单位划分及演化   总被引:4,自引:0,他引:4  
北秦岭富水基性要岩体位于商丹断裂带北侧,为新元古代深成岩岩体。通过1:5万地质填图将该杂岩体划分为5个岩石谱系单位:金盆中细粒石岩单元、黑潭沟细粒暗色变辉长岩单元、马槽沟中粒变辉长岩单元、丁家沟中粒变辉长闪长岩单元和八里湾变角闪石黑云母二长岩、正长岩单元,合并为一个序列--富水序列。依据接触关系、包括特征确定了其侵入序次,构成了比较完整的岩浆演化序列,在岩石矿物组成、岩体成分、微量元素有稀土元素组  相似文献   

6.
迟广城  林维峰 《辽宁地质》1999,16(4):288-300
辽西务欢池-铁匠各冷地区中生代-晚古生代花岗岩体可划分为十一个填图单元,据岩体形成时间、侵入接触关系,岩体及岩石组构特征,可把这十一个花岗岩填图单元归并为小欧力营和察哈尔山两个超单元,两 个超单元主体岩性为钾长花岗岩和二长花岗岩,岩体成因类型属于壳幔混源型,二者岩源不同,小欧力营超单元同位素年龄为269Ma,侵入时代为早二叠纪,为强力就位,察哈尔山超单元同位素年龄为190Ma,侵位时代为早侏罗纪,岩石糜棱岩化明显,属于被动就位。  相似文献   

7.
北秦岭富水基性杂岩体位于商丹断裂带北侧,为新元古代深成杂岩体。通过1∶5万地质填图将该杂岩体划分为5个岩石谱系单位:金盆中细粒变辉石岩单元、黑潭沟细粒暗色变辉长岩单元、马槽沟中粒变辉长岩单元、丁家沟中粒变辉长闪长岩单元和八里湾变角闪石黑云母二长岩、正长岩单元,合并为一个序列———富水序列。依据接触关系、包体特征确定了其侵入序次,构成了比较完整的岩浆演化序列,在岩石矿物组成、岩石化学成分、微量元素及稀土元素组成上具有明显的同源岩浆演化特征,形成于北秦岭新元古代活动大陆边缘的岛弧构造环境。  相似文献   

8.
雪花顶岩体形成于志留纪,为由5个侵入次组成的复式岩体,侵入于寒武纪地层,与泥盆纪地层呈沉积接触,主要岩性由花岗闪长岩—二长花岗岩组成,主要矿物成分为钾长石、斜长石、石英、黑云母,少量角闪石。早侵入次单元岩体内暗色微粒包体发育。综合研究表明:雪花顶花岗岩主要为壳幔岩浆混合成因,岩浆主要来源于地壳部分熔融,其中亦有地幔物质的混染.  相似文献   

9.
李伍秤  王涛 《河南地质》1996,14(1):21-28
北秦岭造山带狮子坪地区出露部分海西期花岗深成岩体。通过1:5万狮子坪幅区调,将其划分为两个单元归并为一个超单元。本文从岩体地质、岩石学、岩石化学和地球化学等方面对其成因类型和构造环境进行研究,并对岩体变形组构进行分析,探讨岩体的就位机制。  相似文献   

10.
北秦岭太白岩体岩石谱系单位划分及侵位时代确定   总被引:8,自引:0,他引:8  
北秦岭太白岩体位于商丹柳构造带北侧,为不同时代表成的复式深成岩体。通过1:5万区域地质填图将该岩体共划分7个岩石谱系单位,厘定为2个超单元,即北部的五里峡超单元和南部的红岸河单元,依据同位素测年结果和超单元间相互关系,确定五里峡超单元主体侵位时代为志留纪,红崖河超单元侵位时代为三叠纪,从岩体周边到中心,从北到南,侵位时代从早到晚,显示半环带状侧向推挤移侵位形式,岩石地球化学资料研究证明,五里峡超单元形成于活动陆缘火山弧构造环境,岩浆源于中上地壳,红岩河超单元形成于同碰撞构造环境,岩浆源于中下地壳。  相似文献   

11.
江苏赣榆城头地区中生代侵入岩岩石谱系单位划分   总被引:2,自引:2,他引:0  
城头地区中生代侵入体经地面调查和对比分析,初步建立了夹山、朱苍2序列共7个单元,其矿物成分、结构构造、岩石化学、地球化学特征有一定的演化规律,根据同位素年龄及区域地质资料,确定夹山序列为早白垩世侵入岩,朱苍序列为晚侏罗世或更早的侵入岩,两个序列皆属Ⅰ型花岗岩,岩浆来源初步认为是上地幔与下部地壳经同熔作用的产物,侵位机制为受北东向构造控制的被动式侵位。  相似文献   

12.
A new database of 70 U–Pb zircon ages (mostly determined by SHRIMP) indicates that the South Patagonian batholith resulted from the amalgamation of subduction-related plutons from the Late Jurassic to the Neogene. Construction of the batholith began with a voluminous, previously undetected, Late Jurassic bimodal body mainly composed of leucogranite with some gabbro, emplaced along its present eastern margin within a restricted time span (157 to 145 Ma). This episode is, at least in part, coeval with voluminous rhyolitic ignimbrites of the Tobífera Formation, deposited in the deep Rocas Verdes Basin east of the batholith; this was the last of several southwestward-migrating silicic volcanic episodes in Patagonia that commenced in an Early Jurassic extensional tectonic regime. The quasi-oceanic mafic floor of the basin was also contemporaneous with this Late Jurassic batholithic event, as indicated by mutually cross-cutting field relationships. Changes in subduction parameters then triggered the generation of earliest Cretaceous plutons (Cretaceous 1: 144–137 Ma) west of the Late Jurassic ones, a westward shift that culminated at 136–127 Ma (Cretaceous 2) along the present western margin of the batholith. Most mid- to Late Cretaceous (Cretaceous 3: 126–75 Ma) and Paleogene (67–40 Ma) granitoids are represented by geographically restricted plutons, mainly emplaced between the previously established margins of the batholith, and mostly in the far south; no associated volcanic rocks of similar age are known at present in this area. During the final Neogene stage of plutonism (25–15 Ma) a recurrence of coeval volcanism is recognized within and east of the batholith. Typical εNdt values for the granitoids vary from strongly negative (− 5) in the Late Jurassic, to progressively higher values for Cretaceous 1 (− 4), Cretaceous 2 (− 0.7), Cretaceous 3 (+ 2) and the Paleogene (+ 5), followed by lower and more variable ones in the Neogene (− 1 to + 5). These variations may reflect different modes of pluton emplacement: large crustal magma chambers developed in the early stages (Late Jurassic to Cretaceous 1), leading to widespread emplacement of plutons with a crustal signature, whereas the Cretaceous 2, Cretaceous 3 and Palaeogene parts of the batholith resulted from incremental assembly of small plutons generated at greater depths and with higher εNdt. This does not in itself justify the idea of a reduction in crustal character due to progressive exhaustion of fusible material in the crust through which the magmas passed.  相似文献   

13.
The Mount Stuart batholith is a Late Cretaceous calc-alkaline pluton composed of rocks ranging in composition from two-pyroxene gabbro to granite. Quartz diorite is most abundant. This batholith may represent the plutonic counterpart of the high-alumina basalt association. A petrogenetic model is developed in which this intrusive series evolved from one batch of magnesian high-alumina basalt, represented by the oldest intrusive phase, by successive crystal fractionation of ascending residual magma. However, the possibility that this intrusive suite originated from an andésite (quartz diorite) parent by fractionation cannot be excluded.Computer modeling of this intrusive sequence provides a quantitative evaluation of the sequential change of magma composition. These calculations clearly indicate that the igneous suite is consanguineous, and that subtraction of early-formed crystals from the oldest rock is capable of reproducing the entire magma series with a remainder of 2–3% granitic liquid. This model requires that large amounts of gabbroic cumulate remain hidden at depth- an amount equal to approximately 8–10X the volume of the exposed batholith. Mass balances between the amounts of cumulate and residual liquid calculated compare favorably with the observed amounts of intermediate rocks exposed in the batholith, but not with the mafic rocks.Mafic magmas probably fractionated at depth by crystal settling, whereas younger quartz diorite and more granitic magmas underwent inward crystallization producing gradationally zoned plutons exposed at present erosional levels.  相似文献   

14.
New U-Pb zircon ages for the Lamarck Granodiorite, associated synplutonic gabbro and diorite plutons, and two large mafic intrusive complexes that underlie them in the Sierra Nevada batholith are 92±1 Ma. These ages establish the Late Cretaceous as a period of extensive mafic-felsic magmatism in the central part of the batholith, and confirm the significance of mafic magmatism in the evolution of the voluminous silicic plutions in the Sierran arc. The lack of significant zircon inheritance in any of the units analyzed supports isotopic evidence that the Lamarck and other Late Cretaceous Sierran plutons were derived predominantly from young crust. Recognition of an extensive mafic-felsic magma system in the Sierra Nevada batholith emphasizes the importance of basaltic liquids in the evolution of continental crust in arc settings.  相似文献   

15.
花坤头营子侵入岩是花坤头营子旋卷构造的重要组成部分,共分出4个侵入体,分别为早石炭世辉绿岩、早三叠世闪长岩、中侏罗世二长花岗岩、早白垩世花岗斑岩,最晚还有一期流纹斑岩脉侵入.岩浆来源除早石炭世辉绿岩来自上地幔,余下几个序次来源于下地壳,并熔融了部分陆壳物质.以被动就位机制为特征.  相似文献   

16.
李家振  刘文灿 《现代地质》1997,11(1):102-110
位于大别山北麓的北淮阳金寨—苏仙石地区广泛发育花岗岩类侵入岩,同位素年龄为140~97Ma,时代属J3—K1。根据侵入岩的地质、岩石学和岩石地球化学特征,将本区侵入岩划分为3个超单元(包括10个单元)和3个独立单元,分属中性岩和酸性岩两大类,岩石类型有闪长岩、二长岩和花岗岩等。根据岩石化学的判别结果,侵入岩均属亚碱性系列中的钙碱性岩石,并属于普通型和钾质型  相似文献   

17.
鲁东晚中生代热隆-伸展构造及其动力学背景   总被引:2,自引:0,他引:2  
为理清山东省鲁东地区晚中生代构造-岩浆-成矿的关系及其发生的动力学背景,本文综合分析了晚中生代侵入岩的空间分布、组合特征、成因类型、形成时代和序列、地球化学演化及形成的构造环境等。研究表明:该区侵入岩由侏罗纪陆壳重熔型花岗岩、白垩纪壳幔混合型花岗岩、白垩纪深源花岗岩和白垩纪脉岩组成,并且从早期到晚期,侵入岩的岩石化学成分由高钾钙碱性系列向橄榄安粗岩系列演化,微量元素由高Ba、Sr花岗岩向低Ba、Sr花岗岩演化,稀土元素由无或弱正铕异常向显著负铕异常演化,岩浆岩成因由S型向I型、A型演化。强烈的岩浆活动和复杂的岩浆岩类型指示了剧烈的壳幔相互作用过程,认为鲁东地区在早白垩世处于强烈的拉张构造环境,其在140~110 Ma期间大规模岩浆活动的同时发生了强烈的地壳隆升事件。通过对断陷盆地、火山活动、变质核杂岩和断层系统的类型、性质、控制因素等进行综合分析,提出它们是大规模伸展构造的表现形式,伸展构造的活动时间为130~98 Ma。进一步分析表明,鲁东地区的白垩纪构造-岩浆组合构成了热隆-伸展构造,它们是太平洋板块俯冲与燕山运动主变形时期(岩石圈增厚)后续效应的产物,岩石圈拆沉、地壳减薄和克拉通破坏是引起早白垩世热隆-伸展构造的根本原因,热隆-伸展构造为胶东大规模成矿提供了有利条件。  相似文献   

18.
The Late Paleozoic intrusive rocks, mostly granitoids, totally occupy more than 200,000 km2 on the territory of Transbaikalia. Isotopic U-Pb zircon dating (about 30 samples from the most typical plutons) shows that the Late Paleozoic magmatic cycle lasted for 55–60 m.y., from ~330 Ma to ~275 Ma. During this time span, five intrusive suites were emplaced throughout the region. The earliest are high-K calc-alkaline granites (330–310 Ma) making up the Angara–Vitim batholith of 150,000 km2 in area. At later stages, formation of geochemically distinct intrusive suites occurred with total or partial overlap in time. In the interval of 305–285 Ma two suites were emplaced: calc-alkaline granitoids with decreased SiO2 content (the Chivyrkui suite of quartz monzonite and granodiorite) and the Zaza suite comprising transitional from calc-alkaline to alkaline granite and quartz syenite. At the next stage, in the interval of 285–278 Ma the shoshonitic Low Selenga suite made up of monzonite, syenite and alkali rich microgabbro was formed; this suite was followed, with significant overlap in time (281–276 Ma), by emplacement of Early Kunalei suite of alkaline (alkali feldspar) and peralkaline syenite and granite. Concurrent emplacement of distinct plutonic suites suggests simultaneous magma generation at different depth and, possibly, from different sources. Despite complex sequence of formation of Late Paleozoic intrusive suites, a general trend from high-K calc-alkaline to alkaline and peralkaline granitoids, is clearly recognized. New data on the isotopic U-Pb zircon age support the Rb-Sr isotope data suggesting that emplacement of large volumes of peralkaline and alkaline (alkali feldspar) syenites and granites occurred in two separate stages: Early Permian (281–278 Ma) and Late Triassic (230–210 Ma). Large volumes and specific compositions of granitoids suggest that the Late Paleozoic magmatism in Transbaikalia occurred successively in the post-collisional (330–310 Ma), transitional (305–285 Ma) and intraplate (285–275 Ma) setting.  相似文献   

19.
本文对班戈雪如岩体似斑状二长花岗岩进行了LA-ICP-MS锆石U-Pb定年、微量元素和全岩地球化学研究,探讨了其形成年代、成岩条件和构造背景。结果表明雪如岩体侵位于晚白垩世晚期(76±1 Ma),锆石饱和温度计和锆石Ti温度计计算其成岩温度分别为760~810℃和738~814℃,较低的锆石相对氧逸度反映成岩环境为还原环境。全岩地球化学分析结果显示其具有高硅、富碱和准铝质--弱过铝质特征,大离子亲石元素和LREE富集,高场强元素和HREE相对亏损。雪如岩体是中地壳部分熔融的产物,源区残留相为斜长角闪岩相,岩浆结晶过程中发生角闪石和斜长石的分离作用。地球化学投图结合区域构造演化显示其形成于后碰撞伸展环境,表明班公湖-怒江缝合带中段地区在晚白垩世晚期已经进入后碰撞伸展阶段。  相似文献   

20.
王贝  李鹏  刘智贤  程龙  闫磊  王卫军 《地质通报》2016,35(9):1479-1487
西藏谢通门县一带区域上属于冈底斯花岗岩带南亚带,侵入岩极其发育,目前填绘有白垩纪、古近纪和新近纪岩体。通过同位素年代学研究,获得12个锆石的U-Pb同位素年龄数据,在原划归白垩纪、古近纪和新近纪岩体中解体出侏罗纪侵入体,按其岩石类型特征,归并为早侏罗世东热村序列和中侏罗世东嘎乡序列。其中,在约拉嘎莫岩体中获得锆石U-Pb同位素年龄166.9±2.8Ma,时代为中侏罗世巴柔期。  相似文献   

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