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1.
经历了复杂多期变形的片岩和片麻岩地区,褶皱形态及形成时代的判定是变质岩构造地质过程研究的难点之一。变斑晶内包裹物迹线记录了区域变质变形作用历史过程,可为通过野外露头观测难以确定的复杂褶皱形态判定提供新的研究途径。本文以美国科罗拉多州阿肯色河Texas Creek地区为例,尝试运用垂直于5期面理弯切轴的定向薄片中叠加面理(变斑晶包裹物迹线)由水平到竖直和由竖直到水平的几何形状变化,确定研究区内一个存在争议的复杂褶皱形态为背形,并推断该褶皱形成于区域内第1期变斑晶生长过程(约为1 500 Ma)中。 相似文献
2.
石榴石Lu-Hf、原位独居石U-Pb定年对多期变形的时代制约——以北祁连托勒牧场为例 总被引：2，自引：1，他引：1
多期变质变形事件的精确年代限定是造山构造年代学研究的热点问题之一。本文尝试运用面理弯切轴测量技术,结合石榴石Lu-Hf和原位独居石U-Pb定年,厘定北祁连托勒牧场地区石榴石和斜长石斑晶记录的两期构造变形事件:石榴石斑晶生长记录的早期构造变形事件年代为512.3±2.7Ma;斜长石斑晶生长记录的晚期构造变形事件年代不早于481.0±2.3Ma,并推断该期构造变形水平挤压主应力方向为北东-南西。斜长石斑晶内未发现独居石,用于年代学测试的独居石颗粒均位于斜长石斑晶外基质中。显微构造分析认为,独居石生长不早于斜长石斑晶。481.0±2.3Ma的独居石U-Pb年龄,应为斜长石斑晶所记录构造变形的时代下限。结合前人锆石U-Pb定年和Hf同位素研究结果分析认为,获得的512.3±2.7Ma石榴石-全岩Lu-Hf等时线年龄,代表了祁连洋俯冲过程中石榴石的生长时间,后期变质变形作用未对石榴石的Lu-Hf同位素体系产生明显影响。结合显微构造分析,石榴石Lu-Hf定年可为早期构造变形提供有效年代学制约。 相似文献
3.
变斑晶包体形迹研究的几个问题 总被引：1，自引：0，他引：1
变斑晶是联系变质与变形的重要媒介。变斑晶内的包体按几何形态可分为９大类。在发生递进变形的变质岩中，斑晶成核生长于变形分解作用的递进缩短带内。除少数螺旋状石榴石外，产于共轴或非共轴递进不均匀缩短变形过程中的斑晶不发生旋转。在韧性剪切带中，由于存在变形分解作用，在岩石发生递进变形过程中，产于共轴或非共轴递进缩短带内的变斑晶也不发生旋转。利用未旋转斑晶中包体形迹可以确定早期面理的取向，寻找构造演化时间标志，确定变形变质关系及其演化史。如在大背坞地区，根据黄铁矿变斑晶的旋转演化，可以恢复韧性剪切带的成生演化历史。近十几年来由于计算机模拟的引人，使变斑晶微构造研究从定性步入定量阶段。 相似文献
4.
提要：美国东部阿巴拉契亚造山带北端缅因州Rangeley地区志留—泥盆纪中温低压片岩测得的面理弯切轴与褶皱轴面数据有很好的对应关系。西部科迪勒拉造山带落基山脉南端科罗拉多州阿肯色河地区Texas Creek 以东高温低压前寒武纪堇青石片岩中测得的褶皱轴面方向和片理走向数据与该地区堇青石、斜长石变斑晶内测得的5期面理弯切轴也表现出很好的一致性。而在Rangeley北东200 km的佛蒙特州Chester Dome地区奥陶—泥盆纪中温中压片麻岩中测得的类似褶皱轴面数据却只反映了该地区5期面理弯切轴中较晚的北北西-南南东走向和北北东-南南西走向的两期面理弯切轴,未测得与其余3期面理弯切轴对应的褶皱轴面数据。通过对变质峰期温度相近、压力不同的两个造山带内3个典型变质岩区面理弯切轴、褶皱轴面方向和片理走向数据的对比分析认为,造山作用发生的地壳深度差异是早期褶皱经历多期造山运动后能否保存下来的主要影响因素。重力形成的去褶皱作用使得早期形成的规模较小褶皱经历复杂造山过程后难以保存。区域内早期形成的规模较大褶皱和造山过程晚期形成的褶皱由于受到重力塌陷作用影响较小,所以能够较好保存下来。 相似文献
5.
韧性剪切带中,由于变形分解作用的存在,岩石发生递进变形过程中,产于共轴或非共轴递进缩短带内的变斑晶不发生旋转,而变斑晶内的包裹体痕迹是递进变形过程中遗留在变斑晶内的变形变质痕迹。利用未旋转斑晶中的包裹体痕迹可以确定早期面理的取向,寻找构造演化的时间标志,确定变形变质的关系及其演化史。对北祁连托勒牧场大型走滑韧性剪切带中石榴石、黑云母等变斑晶及包裹体痕迹的研究,揭示了变斑晶的生长和包、裹体痕迹与褶劈理的演化有着重要联系以及剪切变形过程中变形变质演化史、应变速率的变化。递进变形相应地发生递增变质,但两者存在着一定的差异性。 相似文献
6.
韧性剪切带中，由于变形分解作用的存在，岩石发生递进变形过程中，产于共轴或非共轴递进缩短带内的变斑晶不发生旋转，而变斑晶内的包裹体痕迹是递进变形过程中遗留在变斑晶内的变形变质痕迹。利用未旋转斑晶中的包裹体痕迹可以确定早期面理的取向，寻找构造演化的时间标志，确定变形变质的关系及其演化史。对北祁连托勒牧场大型走滑韧性剪切带中石榴石、黑云母等变斑晶及包裹体痕迹的研究，揭示了变斑晶的生长和包、裹体痕迹与褶劈理的演化有着重要联系以及剪切变形过程中变形变质演化史、应变速率的变化。递进变形相应地发生递增变质，但两者存在着一定的差异性。 相似文献
7.
变斑晶包体形迹研究的几个问题 总被引：1，自引：0，他引：1
高坪仙 《前寒武纪研究进展》1997,20(4):55-63
变斑晶是联系变质与变形的重要媒介。变斑晶内的包体按几何形态可分为９大类。在发生递进变形的变质岩中，斑晶成核生长于变形分解作用的递进缩短带内。除少数螺旋状石榴石外，产于共轴或非共轴递进不均匀缩短变形过程中的斑晶不发生旋转。在韧性剪切带中，由于存在变形分解作用，在岩石发生递进变形过程中，产于共轴或非共轴递进缩短带内的变斑晶也不发生旋转。利用未旋转斑晶中包体形迹可以确定早期面理的取向，寻找构造演化时间标 相似文献
8.
《西北地质》2016,(2)
梅子垭组是汉阴北部地区出露面积最大的地层,岩性主要为白云母石英片岩、含碳白云母石英片岩、含石榴子石黑云母变斑晶白云母石英片岩等,石榴子石和黑云母变斑晶在该岩层中普遍发育。该岩组构造变形复杂,经历了多期构造活动和变质变形过程。笔者在野外调查的基础上,通过分析研究区石榴子石、黑云母变斑晶的关系,采用石榴子石-黑云母地质温度计,对该区广泛出露的含石榴子石黑云母变斑晶白云母石英片岩进行研究,得到如下结论:研究区存在3期黑云母和石榴子石,石榴子石变斑晶具有明显的生长环带,而黑云母变斑晶没有环带;研究区变质作用的变质温度范围为介于511~572℃,主要为530~560℃;变质压力范围为0.16~0.84GPa,变质相属高绿片岩相。 相似文献
9.
三波川变质带位于亚洲大陆的东部边部,构成西南日本侏罗系杂岩体的一部分,它的俯冲可能与在赤道区形成的Kurosgaua地体的碰撞有关。三波川片岩第一带变形发生在韧性条件下,构造置换方向为N30°E,与大陆边缘平行,变形过程中伴有鞘褶皱及矿物拉伸线理的形成。在此阶段,发生大量矿物反应,并伴有变斑晶如石榴石、钠长石的同构造生长,它们在生长过程中发生以垂直流动方向为轴的旋转。变斑晶中的矿物包裹体研究表明,这期变形作用一直持续到变质作用的退变阶段。在本期变形的较晚阶段,发生周态变质的超基性、基性岩石的侵位,高温榴辉岩体的侵位使得角闪片岩发生榴辉岩化进变质作用,并发生接触变质。变质相系由绿纤石 相似文献
10.
理想状态下 ,晶体的生长是各向均匀的。但是 ,近年来变形作用与变斑晶生长关系研究表明 :变形变质过程中变斑晶并不是从中心各向同性地均匀生长 ,其生长与当时所处的应力环境、物质供给和流体相的参与有关。其中流体相的参与是变斑晶生长所需物质迁移的载体 ,为变斑晶生长的物质供给提供先决条件。变斑晶的生长不是连续的而是呈阶段性生长 ,变斑晶的生长相是与变形相相互消长的。变形变质过程中 ,变形与变斑晶生长阶段的关系可总结如下 :(1)变斑晶在未变形域或弱变形域成核后 ,晶体生长所需的物质供应充足时 ,晶体的生长是围绕晶核均匀生长… 相似文献
11.
Foliation Intersection/Inflection Axes within porphyroblasts (FIAs) allow the chronological and kinematic linking of deformation episodes with associated metamorphism. Measurement of FIAs in the Mesoproterozoic Eastern Fold Belt (EFB) of the Mount Isa Inlier, NE Australia, has revealed phases of deformation and metamorphism that could not previously be distinguished from one another. Both the ‘asymmetry switch’ and ‘FitPitch’ FIA measurement techniques have been applied to key localities of polymetamorphosed and multiply deformed EFB, and they yielded the same result. These independent techniques have revealed (1) E–W trending structures that formed during N–S bulk shortening (D1) and associated metamorphism (M1) formed during a period of orogenesis (O1) and N–S oriented structures that formed during E–W bulk shortening (D2) and associated metamorphism (M2) during a period of orogenesis (O2), and (2) the crustal scale tectonic processes associated with polymetamorphism. Middle to upper amphibolite facies metamorphic conditions occurred during O1 with crustal thickening followed by near-isothermal decompression leading to low-pressure/high-temperature (LP/HT) conditions with the emplacement of Williams and Naraku Batholiths around 1550 Ma. This was followed by a second period of middle-to upper-amphibolite facies metamorphism, O2. This history not only correlates better across the EFB, but also with the tectono-metamorphic model recently proposed for the Mesoproterozoic Georgetown Inlier of the north Australian Craton. 相似文献
12.
M. SAYAB 《Journal of Metamorphic Geology》2006,24(2):89-105
Mesoproterozoic terranes of the Australian craton exhibit complex tectonometamorphic histories that are generally considered to result from low-pressure/high-temperature (LPHT) metamorphism with an anticlockwise pressure ( P )–temperature ( T ) path. Yet studies regarding the nature of the P–T history and tectonic regime that led to such a LPHT signature have been quite limited. A foliation intersection/inflection axes preserved in the porphyroblast (FIA) analysis combined with textural relationships and P–T pseudosections, using a key locality of the Eastern Fold Belt of the Mt Isa Inlier, has resolved the cause of the LPHT signature in this region. Two periods of porphyroblast growth have been distinguished using a change in FIA trends with time; the first formed during N–S shortening and the second during W–E shortening orogenesis (D1 & D2, respectively). Significantly, D1 porphyroblasts preserving W–E FIAs are minerals of the Barrovian style, whereas D2 formed porphyroblasts preserving N–S FIAs are Buchan in style. This is consistent with the emplacement of the Williams/Naraku Batholiths after D1 around the onset of D2. Higher-pressure garnet cores, that can be modelled in MnNCKFMASH P–T pseudosections, preserve early W–E FIA and formed during D1. This was followed by decompression and then LPHT metamorphism and deformation during which N–S FIAs were preserved within porphyroblasts. This is supported by the presence of at least two generations of staurolite that crystallized before and after andalusite/cordierite. Middle to upper amphibolite facies metamorphic conditions occurred during D1 with crustal thickening followed by near-isothermal decompression leading to LPHT conditions. This was followed by D2 and a second period of middle to upper amphibolite facies metamorphism that obliterated and/or obscured the tectonometamorphic signature of D1 in the matrix of most rocks. 相似文献
13.
M. Cihan 《Journal of Structural Geology》2004,26(12):2157-2174
Understanding the relationships of inclusion trail geometries in porphyroblasts relative to matrix foliations is vital for unravelling complex deformation and metamorphic histories in highly tectonized terranes and the approach used to thin sectioning rocks is critically important for this. Two approaches have been used by structural and metamorphic geologists. One is based on fabric orientations with sections cut perpendicular to the foliation both parallel (P) and normal (N) to the lineation, whereas the other uses geographic orientations and a series of vertical thin sections. Studies using P and N sections reveal a simple history in comparison with studies using multiple-vertical thin sections. The reason for this is that inclusion trails exiting the porphyroblasts into the strain shadows in P and N sections commonly appear continuous with the matrix foliation whereas multiple vertical thin sections with different strikes reveal that they are actually truncated. Such truncations or textural unconformities are apparent from microstructures, textural relationships, compositional variations and FIA (foliation intersection axis) trends. A succession of four FIA trends from ENE–WSW, E–W, N–S to NE–SW in the Robertson River Metamorphics, northern Queensland, Australia, suggests that these truncations were formed because of the overprint of successive generations of orthogonal foliations preserved within porphyroblasts by growth during multiple deformation events. At least four periods of orogenesis involving multiple phases of porphyroblast growth can be delineated instead of just the one previously suggested from an N and P section approach. 相似文献
14.
近期中国南方页岩气勘查在黄陵隆起南缘的下寒武统和震旦系取得重大突破,本文针对古老地层页岩气构造保存问题,研究黄陵隆起构造演化历史,反演钻井沉积地层埋藏史,通过二维地震剖面解析黄陵隆起南缘的构造学特征,统计分析相关地质年代学数据。认为该区域在约800 Ma经历了花岗岩侵入,形成了以花岗岩为主体的黄陵隆起基底;该区域在800～200 Ma构造较稳定,缺乏这一时期的构造年代学数据;中侏罗世震旦系陡山沱组埋深可达约8 km,晚侏罗世及以后经过多期抬升至现在的构造格局。本研究说明黄陵隆起的古老基底经过元古宙大量花岗岩侵入,可能均质性高而表现为刚性基底,后期所遭受构造改造程度较低,埋深相对较浅。因此,该地区页岩表现为演化程度适中,构造改造弱,后期热事件影响小,有利于页岩气的保存,是目前黄陵隆起南缘获得页岩气勘查突破的关键。并指出南方具有类似构造的雪峰山隆起、神农架背斜和汉南古陆周缘具有良好的下寒武统页岩气勘查潜力。 相似文献
15.
A similar succession of Foliation Inflection/Intersection Axis (FIAs) trends preserved within porphyroblasts is present in two areas separated by 200 km along the Rocky Mountains. The Precambrian rocks in Central Colorado and Northern New Mexico were affected by deformation and metamorphism from ～1506 to 1366 Ma. A succession of five FIAs trending W–E, SSW–NNE, NNW–SSE, NW–SE and WSW–ENE is distinguished in Central Colorado and dated at 1506 ± 15 Ma, 1467 ± 23 Ma, 1425 ± 18 Ma, not dated and 1366 ± 20 Ma respectively. To the south in Northern New Mexico, a succession of five FIAs trending SSW–NNE, WNW–ESE, NNW–SSE, NW–SE and WSW–ENE is distinguished and dated at 1482 ± 48 Ma, 1448 ± 12 Ma, 1422 ± 35 Ma, not dated and 1394 ± 22 Ma. The excellent correlation of the sequence of FIA trends and their ages between regions reveals a sixfold‐FIA succession across the region with the first developed FIA set in Central Colorado not present in Northern New Mexico and the third FIA set in the region not present in Central Colorado. Preferential partitioning of W–E trending deformation into the Central Colorado region ～1506 ± 15 Ma was followed by SSW–NNE trending deformation that affected both regions at 1470 ± 20 Ma. However, preferential partitioning of WNW–ESE trending deformation into Northern New Mexico at 1448 ± 12 Ma left Central Colorado unaffected. Both regions were then affected by the three remaining periods of orogenesis, the first trending NNW–SSE at 1424 ± 15 Ma followed by one trending NW–SE that has not yet been dated, and then one trending WSW–ENE at 1390 ± 19 Ma. This suggests that the Yavapai terrane was tectonized at ～1506 Ma, prior to amalgamation with the Mazatzal terrane ～1470 Ma. Subsequent orogenesis was initially partitioned preferentially into the Mazatzal terrane, but the following three periods of tectonism affected both terranes in a similar manner. 相似文献
16.
Shah Afroz Ahmad 《《地质学报》英文版》2009,83(5):971-984
Abstract: FIAs have been used extensively for more than a decade to unravel deformation and metamorphic puzzles. Orogenic processes developing early during the history or orogenesis challenge scientists because compositional layering in rocks always reactivates where multiple deformations have occurred, leaving little evidence of the history of foliation development preserved in the matrix. The foothills of the Rocky Mountains in Colorado, USA contain a succession of four FIA sets (trends) that would not have been distinguishable if porphyroblasts had not grown during the multiple deformation events that affected these rocks or if they had rotated as these events took place. They reveal that both the partitioning of deformation and the location of isograds changed significantly as the deformation proceeded. 相似文献
17.
茹尔群岛(又称赖于尔群岛)位于东南极普里兹构造带的东部边缘,是一个由太古宙和中元古代岩石组成的复合高级变质地体。中元古代岩石是含有富Fe-Al的含石榴子石-矽线石的费拉副片麻岩组合,经历了格林维尔和泛非两期变质作用。太古宙正片麻岩是含有富Mg-Al的含假蓝宝石的超高温泥质麻粒岩组合(梅瑟副片麻岩组合),主要由经历超高温变质作用的含假蓝宝石的泥质麻粒岩、富Mg的石榴子石-矽线石泥质片麻岩、斜方辉石-矽线石石英岩、含石榴子石镁铁质麻粒岩和钙硅酸盐麻粒岩等组成。其中,含假蓝宝石泥质麻粒岩中石榴子石变斑晶和矽线石集合体(蓝晶石假象)周围分别发育峰期后由假蓝宝石+斜方辉石和假蓝宝石+堇青石后成合晶组成的典型减压结构。含石榴子石镁铁质麻粒岩中石榴子石变斑晶周围则发育峰期后由斜方辉石+斜长石后成合晶组成的典型白眼圈减压结构。不同研究者得出了具有不同超高温峰期条件、峰期前及峰期后演化历史、不同形式的顺时针变质P-T轨迹。对超高温变质事件发生的时间和构造背景的认识也存在较大分歧,有认为超高温变质事件发生于格林维尔期(~1000 Ma)并与碰撞造山和弧岩浆作用有关,也有研究认为发生于泛非期(~590 Ma或~530 Ma)并与普里兹造山及冈瓦纳大陆聚合有关。因此,为理清该区超高温麻粒岩的变质演化历史和构造背景,需要对其进一步进行详细深入的矿物组合-变质结构分析、P-T轨迹重建及高精度的锆石-独居石U-Pb年代学研究,并进行区域上对比。 相似文献
18.
大地构造学研究的新兴前沿课题——造山过程中的流体作用 总被引：5，自引：0，他引：5
流体活动研究已从俯冲带转移到造山过程。主要研究如下几个问题：（１）造山过程中流体的运移方式和分布规律，即造山带古流体场的重建；（２）流体在造山过程中对各种地质作用的参与；（３）造山带演化特征与流体活动幕次的关系；（４）盆山成矿与流体活动的关系等。选择研究程度高、具明显的流体活动特征，同造山成矿发育的年轻造山带或其中一段通过多学科综合研究，将使人们更深入地理解造山过程中的各种地质作用和盆山转化规律及动力学特征。 相似文献
19.
Successions of FIAs(foliation inflection/intersection axes preserved within porphyroblasts) provide a relative time scale for deformation and metamorphism.In-situ dating of monazite grains preserved as inclusions within garnet and staurolite porphyroblasts within the foliations defining each FIA from such successions provides a rigorous approach to grouping ages that formed over extended periods of deformation and metamorphism.Matching age and FIA progressions confirms the suitability of this approach pl... 相似文献
20.
成矿流体研究新进展及研究动态 总被引：1，自引：0，他引：1
本文论述80年代以来流体研究取得的进展及未来的研究动态展望,主要进展表现在构造作用中的地质流体,地壳变形过程中质量和能量的传递;岩浆房附近的孔隙流体压强;水热体系中侵入体空隙渗透性的演化和类型,区域变质作用中的流体动力学,表面水深循环进入到水热变质带和熔融区的氢、氧同位素制约条件,与区域变质作用、地壳深熔作用有关的水热体系,地壳水力学的时间尺度,造山带中的流体作用,消减带的流体作用,二氧化碳的脱气作用。近十年来及未来的研究热点主要表现在将流体的形成和演化与造山作用、构造变形、剪切作用、板块俯冲、壳幔对流等联系起来,俯冲带中的流体、剪切带中的流体、盆地卤水、海底热泉、大陆热泉、成矿流体油气形成及运移、地壳流体与地震火山活动等,对地质流体的成因、特征及其地质作用过程有了更深刻的理解。 相似文献