陕西勉略地区两类混杂岩的发现及其地质意义

陕西勉略地区大地构造位置处于扬子板块和秦岭微板块接合部位,该区混杂岩的发现和厘定是国家基金项目“秦岭勉略构造带的组成、演化及动力学特征”的阶段成果,目前所发现的俯冲型和碰撞—逆冲型两类混杂岩分别位于略阳横现河和勉县长坝,分别称之为横现河混杂岩和长坝混杂岩。 横现河混杂岩:出露横现河镇南张崖沟,呈宽约800～1000m的楔状岩片产出,与南北两侧岩片以向南高角度的韧性逆冲断层接触,属泥砂质混杂岩。混杂岩由大小悬殊形态各异的岩块和基质两部分     

秦岭大别山造山带内巨型构造混杂岩带的组成及构造意义

平行或近平行分布于秦岭大别山造山带的一个巨型构造混杂岩带,由变质表壳岩块、中深地壳变质块体、壳幔过滤带岩块和幔源岩块与糜梭岩和变晶糜梭岩基质共同组成。由构造混杂岩带内岩块和基质的变质变形特点、流变学性质、运动学标志、形成构造环境、动力学特征和时限,表明它们是华北陆块、扬子陆块和分布其间的地体并置碰撞对挤逆冲韧性剪切作用过程中多阶段长时期发育而成。空间上构造混杂岩带内岩块成分的多样性,反映造山带内物     

大兴安岭乌奴耳地区构造混杂岩的组成及地质意义

乌奴耳构造混杂岩由不同性质的岩块和基质组成,属泥沙质构造混杂岩.岩块可分为内部岩块和外部岩块两种类型.岩块大小不一,成分和形态各异,在混杂岩中分布无序.基质为片理化泥质岩或千枚状板岩,剪切变形强烈,面理产状紊乱,绕岩块分布.综合研究表明,乌奴耳构造混杂岩明显区别于沉积成因的滑塌堆积,是典型的泥沙质构造混杂岩,是新林-喜桂图缝合带的重要组成部分.     

四川甘孜生康剪切混杂岩带物质组成、变形特征及演化历史

甘孜生康剪切混杂岩带,它初始发育在陆棚与大陆基之间,是“再生”小洋盆关闭、俯冲－碰撞乃至斜冲剪切、左行走滑综合作用的产物。带内由不同岩性,不同层位,不同时代的构造岩块与遭受强烈剪切变形的粉砂岩、板岩“基质”组合而成。宏观上,无层无序,块体内有序,是造山带特有的非史密斯地层体。     

构造——蛇绿混杂岩工作方法、研究途径及填图单位划分

板块聚敛、洋盆封闭，洋壳残片（蛇绿岩）构造侵位到陆壳（陆源碎屑岩）之上形成了构造－－蛇绿混杂岩。它由以脆性剪切破裂为主的刚性构造包体和以韧－脆性剪切变形为主的剪切基质两部分组成。由构造－－蛇绿混杂岩研究应采用大比例尺精细露头填图，详测剖综合研究方法。同时对构造－－蛇绿混杂岩带填图单位划分方案进行了讨论，提出了对构造－－蛇绿混杂岩带建立杂岩。对蛇绿岩刚性构造块体建立杂岩组合、杂岩体等级体制划分方案；对其它刚性构造块体建立岩片、岩块级非正式地层单位，对剪切基质建立相当与岩组，岩段级非正式地层单位。     

新疆南阿尔金木纳布拉克构造混杂岩带物质组成及变形特征

木纳布拉克构造混杂岩带位于南阿尔金与东昆仑衔接部位,是古阿尔金洋岩石圈板块由南向北阶段性俯冲的产物,为南阿尔金蛇绿岩带的重要组成部分。通过1∶10 000大比例尺填图和剖面测量,结合显微尺度的构造解析,对该构造混杂岩带的物质组成和变形特征进行研究,将与构造混杂岩带有关的物质组成划分为弱变形的“岩块”与强变形的“基质”两类,并从中识别出9种不同岩石组合的岩块及2种不同类型的基质。在对“岩块”和“基质”构造几何学和运动学特征研究的基础上,重点分析了地质体的构造变形截切关系及组合特征,在构造混杂岩带中识别出6期变形作用,建立了相对构造变形序列,为木纳布拉克构造混杂岩带演化提供了新的构造证据。     

内蒙古莫力达瓦旗哈达阳构造混杂岩地质特征及发现的意义

哈达阳构造混杂岩出露于嫩江黑河构造带之中.根据区域地质背景及构造混杂岩中岩块地质及地球化学特征,划分了基质、原地岩块及异地岩块3部分.基质主要为绿帘黑云绿泥构造片岩.原地岩块主要有绿帘黑云绿泥构造片岩及可能来自海沟外缘缓坡的砾岩.异地岩块主要有角闪石岩、混染闪长岩及变酸性火山岩.角闪石岩及混染闪长岩岩石地球化学特征表明,其形成于与消减作用相关的边缘海扩张环境,而变酸性火山岩具有岛弧钙碱性火山岩特征.上述特征说明,哈达阳构造混杂岩与板块俯冲消减-碰撞作用相关.沿红山梁、哈达阳直达依克特一带出露的古生代地层彼此之间均为断块接触,认为在该沿线存在一条早石炭世末的构造混杂岩带.哈达阳构造混杂岩的发现为正确认识嫩江黑河构造带性质,正确分析构造带结构都具有重要意义.     

台湾南部恒春半岛垦丁混杂岩的成因及其构造意义

垦丁混杂岩出露于台湾南部恒春半岛中新世增生楔内,长约20 km,宽最大可达1 km,呈北西-南东向狭长带状分布,大致平行于马尼拉海沟北段,其分布特征类似于与俯冲板块边界相关混杂岩的特征,因此垦丁混杂岩成因的确定对于了解台湾造山带结构及构造演化历史具有重要意义。关于垦丁混杂岩成因,目前主要分为沉积(olistostrome)成因和构造成因两大观点。通过野外观察,垦丁混杂岩的泥质基质普遍发生强烈的剪裂作用,鳞片状结构大量发育,基性或超基性的外来岩块夹杂其中。此外,在垦丁混杂岩内还发现香肠化的砂岩块、由泥质基质充填的脉体及砂岩表面的水压破裂等构造现象。这些现象均反映垦丁混杂岩为构造成因而非沉积成因。垦丁混杂岩体原形成于增生楔底部,并受到一定的高压及应力剪切作用,之后随同卷入的外来岩块及连续沉积地层块体一起沿着马尾逆断层出露于地表浅部,代表南海洋壳向东俯冲于菲律宾海板块之下形成的构造混杂堆积岩体。     

西藏雅鲁藏布江中段构造混杂带特征及其构造意义

<正> 混杂体(Melange)是由板块俯冲过程中所导致的各种构造作用而混杂形成的一些杂乱地质体。它的主要特征是大小不同的各类岩块嵌在比较塑性,遭到强烈剪切作用和破碎作用的基质中,每一混杂体都包括基质(matrix)、外来岩块(exotic block)和原地岩块(native block)三部分。根据其中含有时代新于基质的外来岩块和基质的强烈剪切变形而区别于沉积成因的滑塌体(Olistostrome),又可根据基质的塑性形变和外来成分岩块的普遍出现而区别于一般构造产物(破碎岩、构造角砾岩等)。     

东昆仑南缘布青山复合增生型构造混杂岩带组成特征及其形成演化过程

为了研究东昆仑南缘布青山复合增生型构造混杂岩带的物质组成、构造属性及形成演化历史,在前人资料基础上从构造混杂岩带物质组成、形成时代、构造属性等方面对其进行综合研究.研究结果表明,布青山复合增生型构造混杂岩带是一条分隔东昆仑造山带与巴颜喀拉造山带的增生型构造边界,主要由元古代-古生代不同构造属性的大型构造混杂岩块与混杂基质组成.构造混杂岩块包括中元古代中深变质基底岩块（苦海岩群）、寒武纪蛇绿岩岩块、奥陶纪蛇绿岩岩块、石炭纪蛇绿岩岩块、石炭纪洋岛/海山玄武岩岩块、奥陶纪中酸性弧岩浆岩岩块、格曲组磨拉石沉积等.基质岩系主要为一套强烈构造变形的早中二叠世马尔争组浊积岩系.该混杂岩带记录了东昆仑南缘布青山地区东特提斯洋（布青山洋）自新元古代晚期开启以来,从晚寒武世-中三叠世长期持续向北的洋壳消减及俯冲增生过程,并于中三叠世晚期布青山洋消减完毕而使巴颜喀拉地块与东昆仑地块碰撞拼合.该次造山事件导致了不同类型、不同时代构造岩块与马尔争组浊积岩强烈混杂,最终形成了布青山复合增生型构造混杂岩的基本构造格架.      

川西南乡城——得荣地区的两种混杂岩及其构造意义

混杂岩或混杂堆积是一种奇特的地质现象。早在一个世纪以前,就有过描述和讨论。但是,直到板块构造提出之前,混杂岩没有得到合理的解释。就目前所知,我国台湾、祁连山、西秦岭、喜马拉雅山等地都有混杂岩分布。笔者通过近三年来在金沙江沿岸的地质填图及专题研究证实,四川乡城、得荣一带是混杂岩分布的又一典型地区。     

Structured serpentinite melanges of the Koryak-Kamchatka fold system

The Kuyul, Taigonos, and Upper Khatyrka structured serpentinite melanges at the Pacific continental margin of Northeast Asia considered in this paper are diverse in tectonic setting, age, and geological history. They are characterized by an ordered internal structure expressed in regular arrangement of rock blocks different in composition. These blocks make up mappable tectonic sheets deformed into complex, nappe-related folds. Difference in the block composition of particular sheets is often combined with different composition of serpentinite matrix. The structured melanges of Cape Povorotny (Taigonos Peninsula) and the Kuyul Terrane were formed during accretion of oceanic complexes to a suprasubduction zone and their subsequent juxtaposition. The Upper Khatyrka melange comprises oceanic, island-arc, and marginal-sea complexes. The study of structured melanges makes it possible to ascertain the history of continental accretion and transformation of the oceanic crust. The combination of ordering and chaotic structure allows us to consider structured melanges as manifestations of nonlinear geodynamics.     

青海可可西里地区蛇绿岩的时代及形成环境

青海可可西里地区发现两条蛇绿混杂岩带,它们沿逆冲带分布。古生物、地层和同位素定年资料表明其时代为早石炭世-早二叠世。其岩石组合代表大洋岩石圈残迹。镁铁质岩主要形成于洋岛环境。硅质岩形成于深海、半深海环境,部分生成于洋岛或洋脊附近热水活动区。这是一套弧前蛇绿混杂岩,是古特提斯洋壳俯冲过程中形成的增生楔。这些资料表明,可可西里地区至少在早石炭世就已存在古特提斯洋,洋盆中有一些洋岛,洋盆在早二叠世末期基本闭合。     

Mud diapirism: the origin of melanges in accretionary complexes?

Chaotic melange deposits, a mixture of blocks in a clay matrix, have commonly been attributed to the mechanism of submarine slumping. In the oceans at the present day slumping does not occur on a sufficiently large scale to produce the quantities of melange seen in ancient accretionary complexes. In modern accretionary complexes, massive shale diapirism produces large volumes of melange, and is an entirely adequate mechanism to account for melanges in ancient complexes.     

Franciscan melanges compared with olistostromes of Taiwan and Italy

Details of origin of Franciscan melanges are unknown, although subduction is accepted as the controlling process. Some melanges near plate boundaries in Taiwan and Italy are evidently olistostromes. How do Franciscan melanges compare with these? The Lichi melange and units of “argille scagliose” type in the Northern Apennines rest upon normal marine sediments. The time of accumulation was brief, as shown by limiting time brackets. These key types of evidence for olistostrome origin are rare or absent in the Franciscan, but the pervasive shearing would probably have obliterated such evidence.Similarities between the above-cited olistostromes and Franciscan melanges include the following: argillaceous matrix; large and small blocks of sedimentary rocks and ophiolites; phacoidal and joint-block shapes; soft-sediment deformation in some sandstone; rotation of blocks; extreme dispersal of distinctive rocks; reappearance of older rocks at younger levels. Collectively, these similarities suggest that Franciscan melanges were originally assembled by olistostrome accumulation.Differences between presumed olistostromes and the Franciscan include the following, in addition to stratigraphic relations mentioned above. The Lichi melange shows faint original gross layering where shearing is minimal. Franciscan melanges show various compositional units, but shearing allows tectonic explanations. Blueschist metamorphism is rare or absent in olistostromes of Taiwan and the Northern Apennines. It occurs in the Franciscan not only in random blocks, but also as extensive units of schist and phyllite near the structural top of the complex, toward the “hanging wall” (Great Valley sequence). In the structurally lowest levels, only zeolite facies metamorphism is prevalent. Similar generalities apply to ages of rocks at highest and lowest structural levels. The age distribution would be just the opposite if the entire Franciscan were simply an east-dipping pile of olistostromes.It is concluded that neither subduction alone nor olistostromes alone could have produced all the features of Franciscan melanges, but both played an important role. Critical original features of olistostromes have been modified or destroyed by recurrent underthrusting.     

陕西省勉县白云寺铅锌矿床地质特征

勉县白云寺铅锌矿床位于秦岭复合造山带勉略古岛弧隆起带之勉略蛇绿构造混杂岩带东段,由2条铅锌矿体组成,矿体呈规则脉状赋存于层内韧脆性断裂中,含矿地层为泥盆-石炭系金家河岩组。矿床类型为变质热液型。     

Origin of Franciscan blueschist-bearing melange at San Simeon,central California coast

Block-in-matrix melanges at San Simeon have been variously interpreted as deformed olistostromes or as subduction-channel flow melanges. Detailed examination shows that seven types can be distinguished, with transitions among them. All contain exotic clasts of greenstone, chert, and more rarely blueschist, in addition to greywacke; the same materials also occur as blocks metres to tens of metres in diameter immersed in melange. The seven types are (1) bedded conglomerate, (2) structureless conglomerate, (3) mud-matrix conglomerate, (4) sandy block melange, (5) broken formation, (6) mud-matrix melange without deformational fabric, and (7) sheared melange. Types (1)–(3) are clearly sedimentary in origin. Types (4) and (5) were formed from unconsolidated sediment, most likely by down-slope sliding, and transitional types suggest that the mud-matrix melange (6) formed in the same way. Sheared melange (7) was formed by low-temperature post-consolidational deformation of all other types, which produced shear bands and a crude scaly fabric.

Kinematic indicators of shear direction are rare, but assuming the fabric and shear bands are coeval, the shear direction and sense can be determined from the angular relationship between the two planar fabrics. Most shear planes are gently dipping, with normal-sense displacements of a few centimetres to tens of centimetres. Shear directions are highly variable, with the highest concentrations between WNW and S. This suggests that the main phase of shearing took place during a phase of approximately vertical shortening and horizontal extension, rather than during accretion. Post-accretionary dextral shearing on NNW-trending vertical planes, and sinistral shear on a variety of trends, are likely related to Neogene transform tectonics. The simplest interpretation of these relationships is that the disrupted character of the melanges formed primarily by sliding down the trench inner slope of unconsolidated sediment, including clasts and blocks of previously accreted and exhumed greenstone, chert, and blueschist. The deformational fabric is largely unrelated to the disruption, and was formed during late-stage extension in the accretionary wedge.     

中国的混杂地质体

<正> 随着板块构造学说的问世和发展,混杂地质体愈来愈引起构造地质学者的浓厚兴趣,因为它是古俯冲带或缝合带的主要标志之一。最早研究混杂地质体的当推Griesbash、Diener 和Middlemiss(1883),Kaufmann(1886)在描述阿尔卑斯复理石中的杂乱堆积物时,启用了“野复理石”(Wildflysch),Greenly(1919)首次将“melange”一词引入混杂地质体的研究中,Flores(1955)提出了滑混堆积(Olistostrome)的概念。板块构造学说问世以后,许靖华(1     

YAMDROK MELANGE,SOUTH TIBET

YAMDROK MELANGE,SOUTH TIBET