从实验岩石变形过程探讨四川盆地加里东古隆起的形成机制

岩石力学实验表明,处于脆性、半脆性－半延性域的岩石,其变形经历两个阶段,前期的变形相对均匀分布阶段和后期的变形集中化阶段。把此认识应用于四川盆地加里东古隆起的形成研究中,得到：古隆起及周围岩石圈古生代在区域拉张力的作用下,先经历了变形相对均匀分布阶段,形成了乐山－龙女寺及天井山古隆起;后经历了变形渐进式集中化阶段,先形成了乐山－龙女寺与天井山联合古隆起,后形成了更大范围的联合古隆起;后期阶段的变形     

部分熔融与高级变质岩流变机制——以内蒙古大青山高级变质岩为例

部分熔融作用与高级变质岩变形作用是相互制约,变形作用能够提高岩石部分熔融程度,降低熔融温度。熔体存在影响和制约岩石强度和变形机制。大青山高级岩经历了下部地壳构造层次变质变形和深熔作用改造,形成了复杂构造要素组合。宏观与微观构造特点表明:高级变质岩变形机制主要为熔体增强颗粒边界扩散和颗粒流动,使岩石发生大规模的塑性流动。在宏观上形成了不对称流动组构、熔融线理、岩石和矿物条带、层内底辟褶皱和大型穹窿构造。但是,在微观上矿物颗粒变形不明显,晶内变形组构不发育,表现为三边平衡结构,与静态结晶变质岩结构相似,形成了地壳深部构造层次上变质构造岩-构造片麻岩。     

祁连山玉石沟橄榄岩显微构造特征及演化

橄榄岩作为上地幔的主要成分,影响着上地幔的流变学行为,其显微构造记录了岩石形成发展过程中所经受的构造事件.通过对祁连山玉石沟橄榄岩样品的镜下显微构造观察、岩石组构测定及TEM位错分析,探讨了与变形相关的温度、围压、含水性和应变速率等因素,总结该岩石的变形机制和变形历史,并推断其形成发展时大地构造环境.研究表明,玉石沟橄榄岩产自上地幔,其变形改造经历了上地幔演化和脆-韧性变形2个阶段.上地幔演化阶段橄榄石发育明显的A型原生组构,电子背散射衍射技术（EBSD）测定的橄榄石显微组构表明,该地区橄榄岩形成于高温（＞ 1200℃）、低应力（＜350 MPa）、低应变速率、低含水量的地幔浅部环境条件下;脆-韧性变形阶段叠加改造了原生A型组构,而发育明显的D型次生组构.橄榄石变形主控因素为动态恢复作用,普遍发育亚晶粒、消光带和扭折显微构造等相关组构,并与透射电镜下所观察到的位错排对应,同时还发育以微破裂为主的一套脆性变形组构,表现出两组共轭剪破裂和另一组张性破裂等现象,揭示出与韧性动态恢复现象一致的应力场方向指示.     

华北克拉通基底花岗质片麻岩变形和流变学研究——以辽西寺儿堡地区为例

辽西寺儿堡镇新太古代花岗质片麻岩内发育的宏观、微观构造变形特征表明该地区曾遭受了强烈的韧性变形改造。花岗质岩石变形程度在初糜棱岩–糜棱岩之间,岩石经历了SWW向左行剪切作用改造。岩石中石英有限应变测量判别结果表明,构造岩类型为L-S型,为平面应变。岩石的剪应变平均值为1.43,运动学涡度值为0.788~0.829,指示岩石形成于以简单剪切为主的一般剪切变形中。此外,石英颗粒以亚颗粒旋转重结晶和颗粒边界迁移重结晶作用为主,长石颗粒塑性拉长,部分发生膨凸式重结晶作用;石英组构特征(EBSD)揭示石英以中–高温柱面滑移为主;石英颗粒边界具有明显的分形特征,分形维数值为1.151~1.201,指示了中高温变形条件。综合石英、长石的变形行为、石英组构特征以及分形法Kruhl温度计的判别结果,推断辽西寺儿堡镇新太古代花岗质片麻岩经历过480~600℃的中高温变形,其同构造变质相为高绿片岩相-低角闪岩相。花岗质岩石的古差异应力为10.62~12.21 MPa,估算的应变速率为10~(–11.67)~10~(–13.34) s~(–1),即缓慢的变形,可能记录早期中高温、低应变速率的韧性变形过程,反映华北克拉通基底中下部地壳变形特征。     

内蒙古塔尔气地区佳疙瘩组地质特征及锆石年代学研究

通过对塔尔气地区佳疙瘩组的岩石学、构造、地球化学及锆石年代学等特征的研究,对该组岩石的变形特征、构造背景及形成时代进行了探讨。结果表明,研究区出露的佳疙瘩组以二云母石英片岩、绿泥片岩及石英岩为主,变质矿物组合为:石英+角闪石+黑云母+斜长石,变质程度相当于绿片岩相。锆石LA-ICP-MS U-Pb年代学、岩石地球化学测试分析结果表明,其形成时代应为晚奥陶世晚期,原岩为一套中酸性火山岩。后期经历了两期变质变形事件:第一期应力场为北西—南东向挤压,形成北东向展布的构造线;第二期变形应力场为近南北向挤压,形成近东西向展布的构造线方向,时代可能为早石炭世之后。     

鞍山陈台沟地区太古宙花岗岩组成与构造特征

鞍山陈台沟地区出露有大量太古宙花岗质岩石和变质层状岩系,是研究太古代地壳形成与演化的经典地区之一。通过对该区岩石单元、构造特征研究,较系统地划分了岩石单元,具体分析了各单元组构及构造变形特征。细粒奥长花岗质糜棱岩、似斑状花岗质糜棱岩和中--细粒花岗质片麻岩具有古太古代花岗质岩石的特点,共同经历地壳中--深部层次的韧性变形改造。细粒奥长花岗岩为中太古代岩浆事件的产物,表现为非透入性的变形方式和部分韧--脆性形变组构。鞍山群层状变质岩石主要记录了新太古代中--浅部地壳层次的强烈变形事件。中粗粒白云母花岗岩就位,标志早期不同的构造变形作用在新太古代末期基本结束。在此基础上,讨论了本区太古宙地壳的形成与演化过程。     

太古宙高级变质杂岩的近水平顺层剪切构造变形及岩石深熔作用-以内蒙古大青山地区为例

内蒙古大青山地区是华北地台北缘以富含麻粒岩系和孔兹岩系为特征的高级变质地层发育的地区之一，其中太古宙的岩石普遍经历了麻粒岩相变质与变形作用。在高级变质杂岩中变形构造复杂，其中近南北向和近东西向构造构成了本区的基本构造格局。研究发现，在高级变质地层中还存在着一期近水平顺层剪切构造变形形迹，其形成于下地壳麻粒岩相。近水平顺层剪切构造变形不仅导致麻粒岩系与孔兹岩系以近水平构造面相接触。同时还导致麻粒岩系及孔兹岩系不同程度的熔融。     

辽宁清原—鞍本地区太古宙基底构成

太古宙基底构成一直是揭开地球早期演化历史的关键问题之一,长期以来存在较大争论。解决构成问题行之有效的方法首推详细的区调工作。清原—鞍本地区位于华北地台的胶辽隆起区。区内基底岩石经历了多期变质变形作用的改造,明显发生了“三态”变化,往往发育变形程度不同...     

吉林省夹皮沟太古代岩石分布及变质、变形作用研究

在野外1∶10000地质填图及室内研究工作基础上,认为夹皮沟地区太古代主体岩石是中酸性侵入体(TTG),已变质成为长英质片麻岩。太古代上壳岩以包体形式分布在长英质片麻岩中。太古代岩石经历了三期变质作用和三期变形作用。太古代上壳岩经历韧性变形作用和具有麻粒岩相变质怍用,长英质片麻岩经历早期韧性变形作用和角闪岩相变质作用,而晚期经历脆—韧性变形作用和绿片岩相变质作用。低级变质作用和晚期变形作用改造、叠加早期变质作用和变形作用。     

大别超高压岩石中石英的组构和变形

通过对大别地区不同超高压岩石和同一超高压岩石中不同变形期次石英的变形特征的研究 ,探讨超高压岩石折返时的流变学特征和状态。运用野外构造解析、组构分析、透射电镜和应变分析发现 ,除榴辉岩中静态重结晶石英外 ,其它超高压岩石中石英均发生了强烈的塑性变形 ,波状消光、变形纹、变形条带等极为常见。石英石榴岩中石英交叉滑移位错的发育 ,说明经历了高温位错蠕变 ,其代表的差异应力为Δσ =78.92MPa。石英脉的变形是超高压岩石折返到中地壳以后的角闪岩相退变峰期产物 ,其差异应力为Δσ =2 5 .2MPa。超高压二云母片岩中石英典型的糜棱结构代表的差异应力为 :Δσ =5 9.6 1MPa。大别超高压岩石可能是在构造应力比较低的情况下区域隆升的结果     

高温变泥质岩石中石榴石-黑云母地质温度计的应用——以胶北荆山群富铝岩石为例

在对胶北荆山群麻粒岩相富铝岩石中石榴石、黑云母的成分环带进行深入研究基础上,选取不同粒径、与不同矿物相邻的石榴石、黑云母各微区点成分,利用石榴石-黑云母温度计分别进行了温度估算。确定在黑云母含量较高的岩石(V_(Grt)/V_(Bt)≤1)中,利用大颗粒石榴石(d≥1500μm)晶体核部(或靠近长英质矿物一侧的晶体幔部)成分与基质中远离石榴石等镁铁矿物处于长英质矿物之间的黑云母核部成分配合。通过石榴石-黑云母温度计可以获得相当可信的变质峰期温度。但是对于黑云母含量极低的岩石(V_(Grt)/V_(Bt)≥6),由于黑云母的成分普遍遭到了强烈改造。使得温度估算结果异常偏低,因此不适合采用石榴石-黑云母温度计估算峰期温度。同一岩石中,采用不同的相邻石榴石-黑云母矿物对晶体边缘成分获得的温度值差异较大,反映它们在峰期后发生Fe-Mg交换反应并达到封闭温度平衡状态的程度不同,因此利用石榴石-黑云母温度计难以获得准确的封闭温度。通过热力学计算,建立了一个新的石榴石-黑云母温度计公式。确定胶北荆山群所经历的变质峰期温度为720～770℃,峰期后最低相对封闭温度为480～500℃。     

喜马拉雅结晶岩系中的石榴子石

高喜马拉雅地区广泛分布着一套结晶岩系,它是由前寒武系铁铝榴石-闪岩相的巴罗型区域变质岩系、混合岩和第三纪花岗岩组成。在我国境内聂拉木一带出露宽度达50公里。应思淮(1973)把这套岩系命名为珠穆朗玛群,张旗(1979)把它叫做聂拉木群。对于其中区域变质岩的变质带划分,存在不同的看法。     

软硬相间层状复杂岩体综合变形模量原位试验研究

某拟建大型电站坝基岩体为一套河湖相沉积岩,包含了砾岩、砂岩、粉砂岩和泥岩等多种岩性岩体。不同岩体变形参数各异,常规变形试验只能获得单一岩性岩体的变形模量,而这种软硬相间层状复杂岩体的综合变形模量是与单一岩性岩体变形模量、岩层倾角、岩层厚度多个因素相关的,如何通过试验获得这种复杂组合岩体的综合变形模量是一个重要问题。本文首先对坝址区不同岩性所占的比例进行了详细的统计,获得砂岩、粉砂岩和泥岩的厚度比为6:2.5:1.5,根据这一统计结果在坝轴线附近选择含有砂岩、粉砂岩和泥岩三种岩体的大型变形试验区,将承压板尺寸设定为200cm37cm,承压板就能同时覆盖砂岩、粉砂岩和泥岩三种岩体,且将其厚度比确定为6:2.5:1.5。通过在承压板上施加大荷载（250余吨）将应力传至下部多层岩体,从而获得软硬相间层状复杂岩体的综合变形模量。试验结果表明坝基弱下风化岩体的综合变形模量可达到7.0GPa,已经满足筑坝的要求。通过原位试验成功地论证了坝基岩体综合变形模量量值的问题。      

石榴石流变学研究的某些进展

简要概述了近年来石榴石的晶体结构,高温高压实验,显微构造及其变形机制等领域的研究现状和进展;结合大别山榴辉岩的研究成果,着重讨论了石榴石的变形机制及其运动学特征,认为大别山燕窝榴辉岩中的石榴石经受了两期变形作用;早期变形是在榴辉岩相条件下,表现为塑性变形,其变形机制为简单剪切;而晚期变形则发生在角闪岩相条件下,表现为脆性变形的特点。     

胜利油田下第三系砂岩中阶状石榴石的自生成因及形成温度

本文应用扫描电子显微镜及偏光显微镜,研究重矿物阶状石榴石表面的显微结构,确定它是自生成因的铁铝石榴石。根据阶状石榴石在各探井剖面中的纵向分布规律及特征变化,可以推断它的形成与埋藏深度或地温关系密切。通过计算确定,阶状石榴石初始形成的温度为92±5℃,可作为成岩矿物地温计。这对评价新探区的生油岩及储集岩均有实际意义。     

Mineralogy of New Caledonian metamorphic rocks

A Cretaceous to low-Tertiary sequence of interbedded pelites, cherts, basic and acidic volcanics and calcareous lenses has been metamorphosed by an Oligocene event. A complete intergradational metamorphic sequence is exposed in the Ouégoa destrict. The following metamorphic zones have been recognised: — (1) lowest-grade rocks consisting of quartz-sericite phyllites and pumpellyite metabasalts (2) lawsonite zone, characterized by the association of lawsonite and albite (3) epidote zone, characterised by epidote-omphacite-sodic hornblendealmandine bearing metabasalts and epidote-albite-almandine-glaucophane bearing metasediments; calcareous metasediments may also carry omphacite. The epidote and lawsonite zones are separated by a narrow belt of transitional rocks. Garnets occur in metasediments throughout the lawsonite zone as rare tiny crystals (<0.03 mm diam.). Garnets first appear in metabasalts in lawsonite-epidote transitional rocks. Garnets are widespread and abundant in epidote-zone metasediments and metabasalts. 45 garnets from rocks representative of all lithologies and metamorphic grades have been analysed with an electron-probe microanalyser. The garnets were consistently zoned. Garnets in lawsonite and low-grade epidote zones show a “bell-type” zoning with cores enriched in Mn relative to Fe and rims enriched in Fe, Mg and frequently Ca. Garnets from high-grade epidote-zone metapelites and metabasalts show, in addition, a shallow oscillatory zoning with complimentary variations in Mn and Fe equivalent to 5 mole- % spessartine and almandine. The Fe-for-Mn substitutional zoning, believed to be caused by a diffusion/saturation effect similar to that of the Rayleigh fractional model (Hollister, 1966), appears to have had superimposed on it the effects of parent-rock chemistry and metamorphic grade which control in a complex manner the composition of the cores and the rims of garnets. Garnets from different rock types and metamorphic grade are compositionally distinct. Garnets from lawsonite-zone rocks, irrespective of parent-rock chemistry appear to be spessartine. Garnets from epidote-zone metaigneous rocks and most metasediments are almandine. Garnets from epidote-zone metasediments with bulk-rock compositions which are manganiferous, or have high oxidation ratios, or both, may be spessartine-rich. Garnets from metabasalts are consistently more pyropic in both core and rim compositions than garnets from pelitic metasediments; the pyrope content of cores and rims of garnets from equivalent rock types and mineral assemblages increases with increasing metamorphic grade. Cores of garnets from epidote-zone pelites are richer in grossular than garnets from lower-grade pelites. The reaction which brings almandine garnet into Ouégoa district blueschist assemblages simultaneously with the replacement of lawsonite by epidote involves components of chlorites and sodic amphiboles and can be represented by the following simplified equation: ferroglaucophane+Fe-rich chlorite+lawsonite → glaucophane+Mg-rich chlorite+epidote+almandine.     

变质岩中变斑晶成核生长及旋转问题的述评

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,斑晶的大小受两侧递进剪切变形带的限制。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,斑晶内部包体形迹(Si)反映外部面理(Se)的再活化。利用未旋转斑晶中的包体形迹可以确定早期面理的取向,寻找构造演化的时间标志,确定褶皱轴迹等,本文给出了斑晶中包体形迹弯曲的成因模式图。     

白垩纪以来库车坳陷碎屑重矿物组成变化

碎屑沉积是山脉隆升和盆地沉积的直接记录,包括碎屑重矿物研究在内的碎屑沉积物的分析是开展盆山耦合研究的必要手段。本文对库车坳陷白垩系—新近系砂岩中重矿物含量特征进行了系统的研究,并应用电子探针技术分析碎屑石榴石和电气石的化学组成。研究表明:库车坳陷白垩-新近系源区主要由高级变质岩和沉积岩以及中-酸性火成岩组成。白垩纪和古近纪砂岩中的石榴石富钙镁铝榴石组份,与来自西南天山低温高压变质岩中石榴石组成相似,而新近系砂岩中的石榴石中富铁铝榴石组份,多来自高级变质沉积岩,而非高压变质岩。这些分析表明南天山的大规模隆升和剥蚀发生在渐新世以来,由于它的隆升遮挡了西南天山对库车坳陷的物质贡献。     

Garnet Types from the Cazadero Area, California

This is the third in a series of papers on glaucophane schistsfrom the Franciscan Formation near Cazadero, California. Previouspapers describe three distinct types of glaucophane-bearingFranciscan metamorphic rocks near Cazadero. The purpose of this study is to investigate the garnets presentin metamorphic types III (bedrock schists) and IV (tectonicblocks) as defined by Coleman & Lee (1963). Twenty-fourgarnet analyses are presented. Sixteen of these are from (aragonite-bearing)type III glaucophane schists, and eight are from type IV glaucophaneschists. Type IV rocks include California eclogites. Type III rocks include metabasalt, metachert, metashale, meta-ironstone,and metacarbonate that were formed under high pressure and relativelylow temperature. These rocks contain garnets that display awide range of composition, but the dominant molecules representedare consistently almandine, spessartine, and grossular. Type IV rocks are mainly metabasalts that were probably formedunder higher temperatures and pressures than type III rocks.There is a distinct difference between garnets from type IIIrocks and those from type IV (including eclogites); the lattercontainless spessartine and more pyrope, and the dominant moleculesare almandine and grossular. The four analyses of garnets fromCalifornia eclogites have an average pyrope content of aboutten molecular per cent, and they extend the range of compositionreported for eclogite garnets. Quantitative spectrographic determinations of minor elementsare listed for each of the garnets described. The values determinedfor some of the minor elements have a wide range and a capriciousdistribution over a few feet of outcrop area. As a group, both the garnets from type III rocks and those fromtype IV are pyralspites with large contents (as much as 35 molecularper cent) of ugrandite. This unusual admixture of the pyralspiteand ugrandite garnet series may have resulted in part from theconditions (high pressures and relatively low temperatures)under which the enclosing rocks were recrystallized.     

Rotating garnets

The origin of snowball and sigmoidal inclusion patterns in porphyroblasts is discussed. Snowball garnets are peculiar to shear zones whereas sigmoidal patterns occur in porphyroblasts both in shear zones and on the limbs of folds. There are currently two models for the development of snowball garnets and these have been discussed extensively in the literature. We show that although the typical two-dimensional snowball pattern can be produced by either model, the three-dimensional inclusion patterns are model-specific thus providing a distinguishing criterion. We have applied this criterion to all the available data and find that the classical model, which is dependent on the rotation of garnet relative to a single foliation, is applicable in all cases. Syn-kinematic porphyroblasts on the limbs of horizontal normal folds generally show little rotation relative to geographical coordinates. What rotation they do show generally has the same sense as that of the host limb, but is less in magnitude. This has been used as evidence that the porphyroblasts have remained irrotational while the rocks deformed around them; the implication being that they were unaffected by vorticity associated with folding. This has been explained by claiming that the porphyroblasts are restricted in distribution to small domains of coaxial deformation path. We show that for reasonable deformation models of horizontal normal folds, porphyroblasts affected by vorticity will rotate little with respect to geographical coordinates and our results predict the commonly observed natural patterns. We conclude therefore that lack of rotation relative to geographical coordinates cannot be used to demonstrate that porphyroblasts have grown only in coaxially deforming domains; much less restrictive and more reasonable interpretations are possible. Consequently, the lack of rotation relative to geographical coordinates is more significant for fold modelling than it is for the garnet controversy.