长乐-南澳断裂带晚中生代岩浆活动 与变质-变形关系

长乐-南澳断裂带是东南沿海地区陆内强烈变质-变形带。带内沉积岩、火山岩和早白垩世的钙碱性角闪石黑云花岗岩和花岗闪长岩都已发生可达角闪岩相的变质和石英-长石相韧性剪切变形。鉴于高温矿物和强烈韧性变形多出现在深成岩附近;远离深成岩,变质和变形就逐渐减弱,故本文认为,至少有一部分变质变形的热源是由岩浆提供的。韧剪组构和糜棱质花岗岩是在岩浆侵位的晚期或长乐-南澳断裂带左旋走滑时,在中地壳部位同时形成的,长乐断裂带中花岗岩的组构记录了一期同走滑变形的岩浆作用,“软变形”作用。据此,长乐-南澳带内花岗岩的形成是受走滑剪切应力和岩浆热双重制约的,是在走滑过程中实现的。其动力来源可能与晚中生代的太平洋板块沿日本中央构造线—台湾纵谷带朝东亚陆缘的斜向俯冲有关。     

闽东南基性岩脉形成的构造应力场地质意义

闽东南沿海地处长乐-南澳构造带内,发育晚中生代以来的基性岩脉(岩群),其几何形态和产状记录着区域应力场活动。通过对漳浦赤湖和东山海边基性岩脉的几何形态和产状的分析,推测长乐-南澳带在白垩纪为左旋韧性剪切带,古新世转变成左行脆性剪切带。长乐-南澳带的左旋走滑活动,是由古太平洋板块朝NW斜向俯冲引起的。晚白垩世以来,闽东南应力场性质为剪切与拉张相互变换,指示地壳拉张不是连续的,而是分期次;晚白垩世以来大洋板块属于低应力型俯冲,拉张是东南部主构造。     

福建沿海中生代区域变质带中红柱石、硅线石的形成及其地质意义

福建沿海中生代变质带位于我国东海之滨,呈北东方向狭长条带与海岸线平行展布,大致与长乐——南澳深大断裂带展布方向一致,长约400余公里,宽仅38—58公里。它是由一套中生代晚三叠—晚侏罗世的沉积—火山岩系经区域变质作用、混合岩化作用形成的,其变质时代大致相当于晚侏罗—早白垩世,是一条年青的区域变质带。     

福建沿海中生代区域变质带中红柱石、硅线石的形成及其地质意义

福建沿海中生代变质带位于我国东海之滨,呈北东方向狭长条带与海岸线平行展布,大致与长乐——南澳深大断裂带展布方向一致,长约400余公里,宽仅38—58公里。它是由一套中生代晚三叠—晚侏罗世的沉积—火山岩系经区域变质作用、混合岩化作用形成的,其变质时代大致相当于晚侏罗—     

长乐—南澳变形变质带岩石部分熔融及其与化学成份关系研究

长乐—南澳变形变质带北起福建省长乐,经福清、莆田、晋江、东山、南至广东省南澳岛。全长500余公里,宽40～60公里,为北东向狭长带状热动力变质带,该带控制着福建—广东东南沿海的岩浆活动,变质作用和火山活动,为大陆边缘高热能带。同位素年代学研究表明本带曾有4次构造热事件:第一次为加里东构造热事件,第二次为印支期构造热事件,第三次为燕山期构造热事件,形成大规模的混合片麻岩和花岗岩,第四次为喜马拉雅期变质热事件。为了解该带变质岩、花岗岩的成因和构造演化,笔者进行了福清和东山县有关样品的部分熔融实验。     

北喜马拉雅变质作用和花岗岩研究及春与高喜马拉雅结晶岩系的对比

沿北喜马拉雅（拉轨岗日山脉）分布一条变质－花岗岩带，其变质级别沿垂直于走向方向呈高低起伏变化，而不是单调递增或递减。花岗岩与围岩以和谐过渡为主，岩体不同部位的矿物、岩石成分均有相当程度的变化，熔融程度较低；而高喜马拉雅花岗岩是低共熔的结果。北喜马拉雅变质－花岗岩带与高喜马拉雅结晶岩相比，从变质作用到岩浆活动均有很大的相似性。本文认为，二者形成的构造环境相似，相时间上又有一定的差异。     

俯冲带部分熔融

俯冲带是地幔对流环的下沉翼,是地球内部的重要物理与化学系统。俯冲带具有比周围地幔更低的温度,因此,一般认为俯冲板片并不会发生部分熔融,而是脱水导致上覆地幔楔发生部分熔融。但是,也有研究认为,在水化的洋壳俯冲过程中可以发生部分熔融。特别是在下列情况下,俯冲洋壳的部分熔融是俯冲带岩浆作用的重要方式。年轻的大洋岩石圈发生低角度缓慢俯冲时,洋壳物质可以发生饱和水或脱水熔融,基性岩部分熔融形成埃达克岩。太古代的俯冲带很可能具有与年轻大洋岩石圈俯冲带类似的热结构,俯冲的洋壳板片部分熔融可以形成英云闪长岩-奥长花岗岩-花岗闪长岩。平俯冲大洋高原中的基性岩可以发生部分熔融产生埃达克岩。扩张洋中脊俯冲可以导致板片窗边缘的洋壳部分熔融形成埃达克岩。与俯冲洋壳相比,俯冲的大陆地壳具有很低的水含量,较难发生部分熔融,但在超高压变质陆壳岩石的折返过程中可以经历广泛的脱水熔融。超高压变质岩在地幔深部熔融形成的熔体与地幔相互作用是碰撞造山带富钾岩浆岩的可能成因机制。碰撞造山带的加厚下地壳可经历长期的高温与高压变质和脱水熔融,形成S型花岗岩和埃达克质岩石。     

大别造山带燕山期变质作用与部分熔融:来自混合岩的证据

<正>大陆俯冲碰撞带中高压—超高压岩变质岩的折返以及碰撞后去根过程中往往会伴随着部分熔融,因此对经历过部分熔融作用的岩石的地球化学以及年代学研究是了解俯冲带演化和相关岩石成因的关键。大规模的部分熔融产生巨量的熔体,往往广泛发育混合岩化作用,其带来的热量也会对周围岩体产生后续影响,使其发生不同程度的热变质。目前,岩石的元素地球化学研究以及锆石的U-Pb同位素年代学研究为限定部分熔融及其相关过程的年代与条件提供了重要的依据。     

高压-超高压变质岩石中不同成因的石榴石

石榴石是高压-超高压变质岩石中最重要的变质矿物之一,是研究俯冲带深部变质和熔融过程的理想研究对象.通过对俯冲带内不同条件下形成的石榴石进行详细研究,确定了岩浆成因、变质成因和转熔成因石榴石.岩浆石榴石是岩浆熔体在冷却过程中结晶形成,成分主要为锰铝榴石-铁铝榴石,通常含有石英、长石、磷灰石等晶体包裹体.变质石榴石是在亚固相条件下通过变质反应形成,包裹体为参与变质反应的矿物组合;进变质生长的石榴石通常显示核部到边部锰铝榴石降低的特征.转熔石榴石是在超固相条件下通过转熔反应形成,通常含有晶体包裹体,其中既有从转熔熔体结晶的矿物包裹体,也有转熔反应残留的矿物包裹体.对超高压变质岩石中转熔石榴石的识别,可以为深俯冲陆壳岩石的部分熔融提供重要的岩石学证据,是大陆俯冲带部分熔融研究的重要进展之一.      

华南陆缘晚中生代造山及其地质意义

长乐—南澳带位于华南大陆的东南缘,是揭示晚中生代古太平洋板块与欧亚大陆相互作用和华南陆缘地质演化的一条关键性构造带。该构造带的T3-J含煤地层不整合下伏于下白垩统南园组之下,或以角闪岩相包体形式赋存于晚侏罗—早白垩世片麻状花岗岩体内。这些具有透入性混合岩化特征的副变质岩包体(T3-J)与围岩(片麻状花岗岩)发生过同变形,并且被未变形的白垩纪岩体/脉侵入。这些晚三叠—早侏罗世地层的变质和变形具有朝陆内(NW)方向减弱的特征。下白垩统南园组普遍发生褶皱和绿片岩相变质,并且被未变质的上白垩统石帽山群不整合覆盖。长乐—南澳带的主要岩石单元与构造特征表明华南陆缘在晚中生代经历过两期挤压(造山)。在第一期挤压(造山)过程中,T3-J陆相地层发生褶皱和变质。随后,这些经历了变形和变质的T3-J沉积地层与中-上地壳的其他岩石在早白垩世早期发生构造折返,其间伴随着大规模同构造岩浆作用(147～135 Ma)和区域性混合岩化。在第二期挤压过程中,早白垩世南园组发生褶皱和变质。华南陆缘110～100 Ma的岩浆杂岩、100～90 Ma的A型花岗岩和90～80 Ma的双峰式火成岩可能分别与这次挤压事件及其后的地壳伸展、减薄过程有关。因此,华南晚中生代两大岩浆旋回(165～120 Ma和110～80 Ma)可能受控于同期的两大构造旋回(165～120 Ma和115～80 Ma)。每个构造旋回包括一个地壳受挤压增厚过程和一个随后发生的地壳伸展减薄过程。值得注意的是,华南沿海地区的晚中生代构造-岩浆作用与陆内同期构造-岩浆作用似乎具有可比性。     

Using the isotope dating of endocontact hybrid rocks for the age determination of mafic rocks (southern Siberian craton)

Geological observations and petrological and geochemical criteria are used to detect hybrid rocks at the endocontact of a dolerite dike. The hybrid rocks were produced when the material of a mafic intrusion mixed with a felsic melt. The latter was produced by the melting of the metamorphic rocks making up the Goloustnaya basement inlier of the Siberian craton, under the thermal effect of the intruded dike. Two age groups of zircon have been identified in the hybrid rock by SHRIMP analysis. The Paleoproterozoic age of inherited zircon (1902, 1864, 1859, and 1855 Ma) reflects the contribution of ancient sources to the hybrid-rock composition. The young, primary-magmatic, zircon grains, produced by melting at the endocontact of the mafic intrusion (494 ± 5 Ma), are coeval with the hybrid rocks, and their age indicates when the mafic rocks intruded the metamorphic framework. Dikes of close age, with similar geochemical characteristics, are present on the vast southern margin of the Siberian craton—from Goloustnaya to Biryusa salients.     

Gabbro Akarem mafic-ultramafic complex, Eastern Desert, Egypt: a Late Precambrian analogue of Alaskan-type complexes

Summary ?Gabbro Akarem is a Late-Precambrian concentrically-zoned mafic-ultramafic intrusion located along a major fracture zone trending NE-SW in the Eastern Desert of Egypt. It intruded low-grade metasedimentary rocks, and has a contact metamorphic aureole a few meters wide. This intrusion comprises a dunite core enveloped by clinopyroxene hornblende-bearing lherzolite, olivine-hornblende clinopyroxenite and plagioclase hornblendite. The contacts between the rock types are gradational. They have cumulate textures and the observed crystallization sequence is: olivine ( + cotectic spinel)-orthopyroxene (Opx)-clinopyroxene (Cpx)-hornblende. Mafic minerals from the core of the intrusion are highly magnesian, a consistent increase in the Mg# of olivine (from 69 to 87), Opx (from 62 to 89), Cpx (from 85 to 96) and hornblends (from 62 to 88) is observed from the mafic to the ultramafic units. Spinel has a wide range of Cr# and Mg# ratios. The various rock units define a fractionation trend. The mafic rocks are slightly LREE-enriched relative to the ultramafic units and chondrites. In many aspects, the Gabbro Akarem intrusion is similar to Alaskan-type complexes. Mineralogical and geochemical data suggest that the different rock units were fractionated from a hydrous picritic magma with no apparent crustal contamination. A petrogenetic model involving a rapid rise of hydrous mantle magma along a major fracture zone is proposed. Extensive fractional crystallization led to magma chamber stratification; internal circulation and strong vertical stretching up the center of the rapidly rising diapir increased the rate of magma ascent towards the core. Due to cooling and high viscosity the marginal mafic magma was partly crystallized while the unsolidified core ultramafic magma continued its ascent. As a result, different mineral phases crystallized at different pressure-temperature paths. Field relations, geophysical, petrological and experimental studies support this model which explains many of the characteristics of the Gabbro Akarem and some other concentrically zoned mafic-ultramafic intrusions. Received April 24, 2001; revised version accepted November 20, 2001     

Formation and emplacement of the Dolodrook serpentinite body,Lachlan Orogen,Victoria

Serpentinised peridotite and ultramafic breccia make up an approximately 5 km‐long, 1 km‐wide fault slice within turbidites in the Dolodrook River region of the central Lachlan Orogen. The serpentinite body is surrounded by juvenile, mafic‐ultramafic sedimentary rocks with Cambrian limestone olistoliths representative of locally derived debris flows, and Middle to Upper Ordovician black shale, chert, sandstone and mudstone. The antiformal geometry and nature of the ultramafic breccia and mafic‐ultramafic sedimentary rocks (Garvey Gully Formation) indicate that the serpentinite body may have been either a former oceanic transform fault zone, a Marianas‐style serpentine seamount or a combination of these. Observations of modern‐day forearc regions show that faulting processes have led to the exposure of serpentinised peridotite horst blocks and serpentine mud volcanoes that have intruded along fault conduits (e.g. Marianas and Izu‐Bonin forearcs). At Dolodrook, the structural and metamorphic relationships with the surrounding rocks, and the lithological associations, have much in common with these observations and indicate that Dolodrook may be an ancient, on‐land example of an accreted seamount or oceanic topographic high. Structural relationships, the very low metamorphic grade of all rocks at Dolodrook, and the presence of broken formation developed in not‐fully lithified Middle to Upper Ordovician sandstone and mudstone indicate that the serpentinite body was emplaced at shallow crustal levels within the turbidite wedge (Tabberabbera Zone), possibly as an offscraped topographic high during marginal basin closure. The Dolodrook serpentinite has previously been inferred as part of the Cambrian igneous sequence (‘greenstones’) exposed in the Governor, Mt Wellington and Heathcote Fault Zones, but structural and metamorphic relationships with surrounding rocks, and the Cambrian tectonic setting in which it formed, have remained speculative.     

青海玉龙滩地区托赖岩群中—早二叠世基性岩墙的发现及地质意义

在玉龙滩地区古元古代托赖岩群变质岩中发现了一套基性岩脉侵入体,岩石类型主要为辉长岩、辉绿岩,侵入于托赖岩群片麻岩、片岩,岩脉长轴走向大多以北西向为主,个别近南北向或北东向,露头规模一般长10~35m,宽5~10m。通过同位素测年分析辉绿岩脉地质时代为早二叠世,结合对地质特征、岩石学特征、岩石化学、地球化学特征的研究,认为其属于拉斑玄武系列,形成于伸展性构造环境。结合本区区域地质分析,该岩脉可能为祁连山造山带加里东期造山运动结束之后,由于陆壳加厚而发生伸展崩塌,造成幔源基性岩浆底侵,形成了该类相当于基性岩墙的产物。反映北祁连地区在早二叠世有一期陆壳加厚伸展背景下的基性岩浆底侵事件。     

New 40Ar/39Ar dates from the Las Tazas complex,northern Chile: Tectonic significance

The Atacama Fault Zone is a major Mesozoic structure that trends along the Coastal Batholith of northern Chile. Part of the fault zone underwent a kinematic change from dip-slip to strike-slip displacement during the Early Cretaceous. The Las Tazas complex intruded the fault zone during this change. New analyses of country rock protomylonites from the edge of the complex firmly constrain the age of the change to 130 Ma and confirm that the complex was emplaced during active displacement along the fault zone. The intrusion heated its immediate country rocks and allowed localised ductile shearing during emplacement. Upper crustal intrusions like the Las Tazas complex are ideal targets for geochronological studies of major shear zones.     

衡山地洼花岗岩的断裂重熔成因

衡山复式花岗岩由南岳岩体和白石峰岩体组成,形成于西缘大断裂的剪切阶段,并与韧性变形变质岩、断裂混合岩构成了紧密共生的(两期)三位一体组合。研究表明,白石峰岩体是由早期眼球状混合岩高程度熔融而成的,南岳岩体则是高变质相韧性断层岩重熔的产物,二者均属断裂重熔。重熔过程是一种流体开放体系,重熔作用沿断裂呈线带状发生,与深部高温热流体沿断裂带的注入、聚集有关。断裂重熔是地洼花岗岩的形成方式之一,其实质是地洼块断(造山作用)重熔。     

Clasts of high-grade Sanbagawa schist in Middle Eocene conglomerates from the Kuma Group, central Shikoku, south-west Japan

Middle Eocene conglomerates which overlie the Sanbagawa metamorphic rocks contain clasts of metamorphic rock with isotope ages of 120-85 Ma, which fall within the age range reported from the Sanbagawa metamorphic rocks. They were derived from the chlorite to oligoclase zones of the Sanbagawa metamorphic belt. Clasts of garnet amphibolite and oligoclase-biotite schist show a mineral assemblage similar to the highest grade Sanbagawa schists. However, the metamorphic temperatures estimated by various mineralogical thermometers show that some of the clasts were formed at higher temperatures than the in situ Sanbagawa metamorphic rocks. Such higher grade rocks were at the surface by the Middle Eocene and for the most part they have been eroded away. Cretaceous and post-Cretaceous sediments overlie, or are in fault contact with, the Sanbagawa metamorphic rocks which suggests that rocks in the belt were uplifted and eroded from the latest Cretaceous to Middle Eocene time after strike-slip movement along the Median Tectonic Line. Since the Middle Eocene, the belt has experienced relatively slow uplift which was locally around 2 km in central Shikoku.     

安徽五河地区岩浆岩及构造对金矿的控制作用

为研究五河地区金矿床与岩浆岩、构造之间的内在关系,通过重磁异常推断隐伏岩体的分布特征,研究岩浆岩与金矿床的空间分布关系、成矿流体的同位素特征以及郯庐断裂带对金矿床的控制作用.结果显示金矿床大多位于已知岩体或隐伏岩体的边缘,区内各矿床的成矿流体相似,H-O同位素图解中石英样品点大部分落入岩浆水范围,部分落入变质水范围.岩...     

闽西北铅锌矿成矿特征及控矿条件浅析

闽北地区属华南褶皱系的一部分,其中铅、锌为区内优势矿种,广泛分布于前震旦纪变质岩系中,尤其以前震旦纪龙北溪组的黑云斜长变粒岩、云母片岩、石英片岩中最为多见。其成矿特征可分为热液型铅锌矿床、充填交代型铅锌矿床及沉积变质热液叠加型铅锌矿床。其形成受地层、岩浆、构造（以断裂构造为主）控制较为明显,前震旦系变质岩系中的绿片岩、压扭性断裂及前震旦系变质岩系与岩体的接触带及其附近应是本区铅锌矿床找矿的主要方向。     

The Arunta Inlier: a complex ensialic mobile belt in central Australia. Part 1: Stratigraphy,correlations and origin

The Arunta Inlier is a 200 000 km² region of mainly Precambrian metamorphosed sedimentary and igneous rock in central Australia. To the N it merges with similar rocks of lower metamorphic grade in the Tennant Creek Inlier, and to the NW it merges with schist and gneiss of The Granites‐Tanami Province. It is characterized by mafic and felsic meta‐igneous rocks, abundant silicic and aluminous metasediments and carbonate, and low‐ to medium‐pressure metamorphism. Hence, the Arunta Inlier is interpreted as a Proterozoic ensialic mobile belt floored by continental crust. The belt evolved over about 1500 Ma, and began with mafic and felsic volcanism and mafic intrusion in a latitudinal rift, followed by shale and limestone deposition, deformation, metamorphism and emergence. Flysch sedimentation and volcanism then continued in geosynclinal troughs flanking the ridge of meta‐igneous rocks, and were followed by platform deposition of thin shallow‐marine sediments, further deformation, and episodes of metamorphism and granite intrusion.