共查询到19条相似文献,搜索用时 640 毫秒
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在分析烟台北部芝罘群主要变质岩类的变质矿物共生组合,变质相系及构造岩等特征的基础上,对该群变形,变质作用及演化特征进行了探讨。认为该区芝罘群曾经历1期韧性变形作用和4期变质作用(古元古代高角闪岩相,中元古代早期低角闪岩相,中元古代晚期高绿片岩相及新元古代低绿片岩相变质作用)。 相似文献
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新疆西南天山蓝片岩的变质作用pTDt轨迹及构造演化 总被引:31,自引:1,他引:31
西南天山蓝片岩的变质作用pTDt轨迹显示进变质作用为快速升压过程,退变质作用为近等热降压过程。自俯冲杂岩进入俯冲带到形成蓝片岩后抬升出露于造山带,变质作用经历了浊沸石相(415Ma?)→硬柱石-蓝闪片岩相(408Ma?)→蓝闪绿片岩相(345Ma)→0绿片岩相(314Ma)连续渐变演化的过程。蓝片岩中现存主要蓝闪绿片岩相矿物组合并非峰期变质矿物组合。造山运动晚期的大规模韧性推覆作用促成蓝片岩快速抬 相似文献
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大别山产出的榴辉岩相岩石包括石榴橄榄岩、榴辉岩、榴云片岩、榴辉片麻岩、榴玉英岩和榴辉大理岩等不同系列,它们均分布于花岗质片麻岩中。矿物共生序列研究表明,榴辉岩相岩石经历了从绿帘角闪岩相、柯石英榴辉岩相、角闪榴辉岩相、绿帘角闪岩相到绿片岩相的演化过程。花岗质片麻岩及变质火山—沉积岩系并未经历超高压变质作用,但却与榴辉岩相岩石经历了同一期绿帘角闪岩相变质事件,证明二者在地壳范围内发生了构造合并 相似文献
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桐柏-大别造山带随县群变质变形作用研究 总被引:1,自引:0,他引:1
中新元古代随县群分布于秦岭—大别造山带南部,是一套形成于大陆裂谷环境中的砂页岩—流纹英安质火山碎屑岩建造,并在拉张环境中受到了辉长辉绿岩墙侵入.从新元古代末开始经历了多期变质和变形作用改造,记录了华北与扬子两大陆块及其造山作用的复杂演化历史.以现代变质地质学理论为指导,结合岩石学与构造学,宏观与微观研究,确立了随县群的地质事件序列.其主要有3个变形和变质演化阶段:晋宁期伸展滑脱固态流变,低绿片岩相变质;印支期韧性剪切,绿帘—蓝片岩相变质;早燕山期逆冲推覆,低绿片岩相变质 相似文献
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桂东南云开岩群斜长角闪岩的变质作用PT轨迹及其动力学意义 总被引:1,自引:0,他引:1
桂东南中新元古界云开岩群是一套中浅变质岩系,并形成一系列绿片岩相-角闪岩相的递增变质带,通过对云开岩群角闪岩相变质带(十字石-蓝晶石带)中斜长角闪岩变质作用的PT轨迹的系统研究显示,其包括了由早期绿片岩相变质阶段(M1)→峰期角闪岩相变质阶段(M2)→近等温降压变质阶段(M3)→近等压降温变质阶段(M4)→晚期绿片岩相退变质阶段(M5)五个阶段的顺时针PT演化轨迹,其地质动力学过程属于典型的板块俯冲碰撞→抬升模式,表明云开地块北缘造山带的地质构造演化经历了俯冲碰撞及碰撞后的快速抬升过程。 相似文献
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北京密云麻粒岩相区变质作用演化及PTt轨迹的研究 总被引:4,自引:2,他引:2
北京密云麻粒岩相区在早前寒武纪时期主要经历了两期变质作用。每期变质作用又可划分为三个连续的变质阶段,峰期阶段的P-T条件均达到了麻粒岩相.第一期变质作用约结束于2500Ma,具有与造山带相似的顺时针PTt轨迹,峰期阶段T为800~900℃,P=0.98~1.02GPa,这种轨迹主要与早期平卧褶皱和推覆构造使地壳大幅度增厚有密切关系。第二期变质作用约发生在1800Ma,PTt轨迹为具近等压加热(IBH)特点的顺时针轨迹,峰期阶段T为760~810℃,P为0.96~1.04GPa,这种轨迹与大陆地壳的拉伸作用有密切关系。 相似文献
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中条山地区地质特征及铜矿床类型 总被引:3,自引:0,他引:3
中条山地区出露的地层主要有新太古界涑水麻粒岩-角闪岩相杂岩、绛县群角闪-绿片岩岩相变质岩、古元古界中条群绿片岩相变质岩、担山石群变质砾岩-石英岩、西阳河群安山岩、沉积岩和中新元古界沉积岩.区内岩浆作用强烈,以绛县期、西阳河期火山喷发、涑水期岩浆侵入为主,火山作用为铜矿床的形成提供了大量的成矿物质.深断裂构造和褶皱构造,特别是其交汇处为成矿物质的运移和沉淀提供了空间.按成因该区铜矿床可分为次火山-火山气液再造型、远火山-沉积变质型、沉积变质型、层控热液型和热液脉型铜矿床,代表性矿床有铜矿峪、篦子沟、胡家峪、横岭关、落家河等矿床. 相似文献
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中条山绛县群碎屑锆石LA-ICP-MS U-Pb测年及其地质意义 总被引:5,自引:2,他引:3
中条山位于山西省的南缘,主要由涑水杂岩、绛县群、中条群、担山石群和西阳河群组成.其中绛县群主要由变质的砂岩、半泥质岩、泥质岩、碳酸岩和火山岩组成.在取自绛县群的两个变质沉积岩样品中,利用LA-ICP-MS定年方法,获得85个单颗粒碎屑锆石,锆石年龄主要介于2416~2899Ma之间,样品05ZR02-1中的主峰值年龄为约2667Ma,样品05YQ12-1中的主峰值年龄为约2537Ma,表明这些变质沉积岩主要源于华北克拉通中部带,以晚太古代老地壳物质为主.在这些碎屑锆石中,最年轻的年龄为2160±17Ma,可代表其沉积时的最大年龄,绛县群变质沉积岩的的沉积作用应该发生在2200Ma之后,而不是在晚太古代后的2.5~2.3Ga,绛县群与北峪花岗岩之间并不是呈现侵入接触关系. 相似文献
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中条山地区绛县群和中条群沉积时限:夹层斜长角闪岩SIMS锆石U-Pb年代学证据 总被引:5,自引:4,他引:1
中条山地区出露大量早前寒武纪岩石,是认识华北克拉通晚太古代至早元古代大地构造演化的关键地区。绛县群变质陆缘碎屑-火山岩及中条群变质陆缘碎屑-碳酸盐岩建造是该区最主要的地层单元,同时也是一系列铜矿床的赋矿围岩。目前,对于二者的形成时代仍缺乏直接证据。本文通过高精度的二次离子质谱锆石U-Pb定年,厘定了绛县群和中条群中的斜长角闪岩夹层分别形成于~2189Ma和~2086Ma。结合已有同位素资料,我们认为绛县群变质沉积-火山岩系可能形成于ca.2160~2190Ma,而中条群中段的大理岩和黑色片岩系(余元下组和篦子沟组)形成于ca.2059~2086Ma之间。另外,岩石组合和矿化类型指示,中条山地区在ca.2090~2190Ma可能经历了两次裂谷事件。 相似文献
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闽北前寒武纪变质岩的P—T—t轨迹和其形成的动力学过程 总被引:2,自引:0,他引:2
闻北前寒武纪变质岩是华夏古陆基底的重要组成部分。本文通过对闽北麻源群和马面山群变质岩详细的变质变形关系的研究和石榴子石环带测定P-T-t轨迹的应用,结合构造地质和同位素年代学的资料,证实了麻源群变质岩形成于早元古代或更老年代,在早元古代末期遭受过中压、中高温变质,但在晚元古代晋宁期与中元古代形成的马面山群岩石一起经历了强烈的变质变形作用,表现为早元古代麻源群岩石遭受强烈改造,具有早期地壳再活化特点。麻源群岩石完整的晋宁期变质P-T-t轨迹不支持正常大陆碰撞的假说,它的形成与异常的地幔热流有关,很可能为一种地壳增厚和地幔减薄的动力学模式。 相似文献
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Metamorphic evidence for an inverted crustal section, with constraints on the Main Karakorum Thrust, Baltistan, northern Pakistan 总被引:1,自引:0,他引:1
Abstract The Shyok Suture Zone separates rocks in the Asian plate from rocks in the Kohistan-Ladakh island arc. In Baltistan, this suture has been reactivated by the late 'break-back'Main Karakorum Thrust (MKT). The P-T histories of metamorphic rocks both north and south of the MKT have been determined in an effort to place constraints on the tectonic history of this zone. The terranes north and south of the MKT have different, unrelated metamorphic histories. Rocks from the Kohistan-Ladakh island arc south of the MKT have undergone a static low- P (2–4 kbar, c. 500° C) thermal metamorphism. The P-T paths and metamorphic textures of these rocks are consistent with metamorphism due to emplacement of plutonic rocks into the island arc. This metamorphism pre-dates folding and deformation of these rocks. Rocks in the Karakorum Metamorphic Complex, north of the MKT, have experienced a complex deformational and metamorphic history. Prograde metamorphic isograds have been deformed by subsequent south-verging folding and by gneiss dome emplacement. However, decompression metamorphic reactions occurred during nappe emplacement. Higher pressure rocks are associated with higher level nappes, creating an inverted pressure metamorphic sequence (8–9-kbar rocks over 5–6-kbar rocks). There is little variation in temperature with structural level (550–625° C). These two different terranes have been juxtaposed after metamorphism by the late south-directed MKT. 相似文献
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CHEN Wei‐Min HUANG Young‐Ching Yoshiyuki IIZUKA LO Ching‐Hua WU Hanquan SONG Shuguang YANG Jingsui XU Zhiqin YANG Houng‐Yi 《《地质学报》英文版》2002,76(1):44-62
After the integration of petrographic study, geothermobarometry and Gibbs method, the synthetic P-T paths for the rocks from different geological profiles in the North Qilian, China, have been derived. The composite P-T paths from different methods indicate that all the high-pressure rocks in the Qilian area recorded P-T paths with clockwise loops starting at the blueschist facies, later reaching peak metamorphism at the blueschist facies, eclogite fades or epidote-amphibolite facies and ending up with the greenschist facies. The incremental Ar-Ar dating shows that the plateau ages for the high-pressure rocks range from 410 to 443 Ma. The plateau ages could be used as a minimum age constraint for the subduction that resulted in the formation of these high-pressure rocks in the Qilian area. It is proposed that the late-stage decompressional and cooling P-T paths with ends at the greenschist facies for these high-pressure rocks probably reflect the uplift process which could occur after shifting the arc-t 相似文献
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郯庐断裂带张八岭隆起南段肥东群石榴角闪岩变质P-T演化史对其构造属性的制约 总被引:3,自引:2,他引:1
通过对张八岭隆起南端肥东群中磁铁石榴铁闪石岩的岩相学、矿物成分分析和热力学评价,并结合野外地质填图和共生围岩分析表明,该岩石经历了5期变质作用,展现了顺时针的P-T演化特征,早期阶段表现为近等压升温,晚期阶段为降温降压的过程,其峰期变质平均P-T条件为:524℃和0.49GPa.结合地质背景和郯庐断裂带的演化特征分析,早期过程可能反映的扬子基底所经历的区域变质过程,晚期过程可能是由于郯庐断裂的后期抬升分量所致,不具有造山带的P-T演化特征.对比前人对宿松群的变质演化历史的研究,肥东群和宿松群峰期变质压力差可达0.8GPa,表明两者属于不同变质级别的块体.因而,肥东群和宿松群不能作为被郯庐断裂左行错开的标志层.由此表明,张八岭隆起南段所出露的肥东群变质杂岩,属于扬子板块上的变质基底,郯庐断裂带活动中将其剥露地表,并没有经历过大别造山带的变质作用. 相似文献
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大别山区变质岩中蓝晶石的几种退变质反应及其所指示的动力学过程 总被引:5,自引:2,他引:3
蓝晶石在大别山含柯石英和不含柯石英的榴辉岩、高压变质的副片麻岩、非高压变质的宿松群的变质沉积岩中都是重要的变质矿物。它们多有冠状或其它的变质反应结构,形成多样化的退变质反应矿物。有些退变质反应是十分罕见的。本文报道了8种蓝晶石的矿物组合和退变质反应,推测和计算了变质反应的温度-压力条件,从而探讨了它们代表的近等温降压、升温降压和流体为重要因素的降温降压的不同的动力学过程。这些数据与用其它变质矿物所得到的温度压力条件和PTt演化基本一致。为探讨大别山超高压变质带的构造演化提供了新的依据。 相似文献
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Contact aureoles as constraints on regional P-T trajectories: an example from the Northern Alabama Piedmont, USA 总被引:1,自引:0,他引:1
Abstract Contact aureoles of plutons emplaced into regionally metamorphosed terranes can provide indicators of physical conditions along a portion of regional metamorphic P-T trajectories, thereby allowing reconstruction of more complete P-T loops than would be otherwise possible. In the Northern Alabama Piedmont of the southern Appalachians, Wedowee Group metapelites preserve evidence for two regional metamorphic phases overprinted by contact metamorphism adjacent to the Blakes Ferry Trondhjemite. Textural evidence indicates that an early bt+st+grt assemblage was replaced by bt+chl+grt during the latter stages of regional metamorphism. Changes in AKFM topology, complex Fe-Mg-Ca garnet zoning, and the latestage appearance of epidote indicate that a sequence of continuous reactions (bt+st = grt+ ms followed by chl+ms+Ca-grt+Ca-pl=bt+ (Fe+Mg)-grt+ep) occurred in response to increasing pressure and resulted in the observed changes in mineral assemblage. Pl-ms-bt-grt thermobarometry indicates conditions of 580° 65°C, 8.5±0.8 kbar for equilibration of grt+ bt+chl. Pluton emplacement, subsequent to penetrative deformation, caused textural annealing and mineral re-equilibration by the continuous reaction bt+(Fe+Mg)-grt+ep = chl+ms+Ca-grt+Ca-pl within 50 m of the pluton. Conditions of 510±65°C, 5-7 kbar are inferred. A reconstructed P-T trajectory for this area is characterized by (1) early moderate- T , moderate- P metamorphism; (2) an increase in P to approximately 8.5 kbar; and (3) decompression and slight cooling prior to pluton emplacement. The compressional phase of this path is interpreted to result from underthrusting of the Wedowee metasediments to mid-crustal levels during Palaeozoic crustal thickening. Late-stage decompression prior to intrusion records uplift of these rocks in response to movement on structurally lower thrusts. 相似文献