文象花岗岩的成分、结构和成因机制

文象花岗岩具有特殊文象结构,研究其三维拓扑结构和形成过程有助于了解花岗质岩石的结晶作用.以北京周口店房山岩体和湖北罗田蕙兰山的文象花岗岩为研究对象,综合利用光学显微镜、扫描电镜、电子探针和电子背散射衍射等技术方法,对岩石矿物组成、结晶学取向和拓扑结构进行了系统研究.结果表明:(1) 文象花岗岩的矿物组成与其形成地质环境有关,石英和长石的含量变化范围很大,其中石英含量通常在20%~45%,但是相同地区同期形成的文象花岗岩具有相对稳定的矿物组成;(2) 长石作为寄主矿物通常呈半自形－自形粗大晶体,可以是碱性长石或斜长石,其端元组分以钾长石和钠长石为主,低温下常分解为条纹长石;(3) 石英在长石寄主矿物中规则穿插生长,在三维空间通常呈近似平行板状、长条状/柱状或非连通枝杈状,并只在特定岩石断面形似象形文字;(4) 正交偏光显微镜下,石英可以具有多种消光位,但是通常在一定范围内同时消光;(5) 石英普遍发育道芬双晶,偶见日本双晶;(6) 条纹长石中钾长石与钠长石对应(100)、(010)、(001) 面和[001]轴近似平行;(7) 多数石英颗粒与寄主长石之间具有密切结晶学取向关系,即石英[1123]轴近似平行长石c[001]轴.该研究证实文象花岗岩是石英和长石同时生长的结果,而长石作为寄主矿物影响并控制着石英的成核与生长方向.      

徐淮早白垩世埃达克质岩中含橄榄石单斜辉石岩的成因及其岩石学意义

报道了徐淮地区早白垩世埃达克质岩中首次发现的含橄榄石单斜辉石岩捕虏体的岩相学与矿物化学资料, 该类捕虏体显示堆积结构、块状构造, 主要由单斜辉石(~80%)、斜方辉石(~5%)、橄榄石(~5%)和普通角闪石(~10%)组成.橄榄石外侧发育有斜方辉石反应边, 角闪石沿辉石粒间分布, 呈嵌晶结构.矿物化学分析结果表明: 橄榄石的镁橄榄石分子值(Fo)=77.7~79.3, Ni=623×10-6~773×10-6; 斜方辉石的Mg#=75.6~80.2, Cr=161×10-6~684×10-6, Ni=79×10-6~708×10-6; 单斜辉石的Mg#=84.5~86.4, CaO=21.59%~23.13%, Al₂O₃=1.72%~2.44%.上述矿物与中、新生代玄武岩中橄榄石、斜方辉石和单斜辉石斑晶以及堆积成因辉石岩中的斜方辉石和单斜辉石成分类似.此外, 单斜辉石的稀土配分型式以相对富含中稀土元素的上凸型为特征, 稀土元素含量较低(∑REE=10.14×10-6~12.71×10-6), 无明显的铕异常(δEu=0.90~1.16), 类似于新生代玄武岩中单斜辉石斑晶.捕虏体中的普通角闪石的Mg#=74.0~80.4、SiO₂=43.2%~44.5%、Na₂O=2.04%~2.29%, 稀土元素分馏不明显, 显示亏损高场强元素(HFSEs, 如Nb、Ta、Zr、Hf), 富集Sr、Rb、Ba的特征, 与新生代玄武岩中角闪石捕虏晶成分不同.结合其嵌晶结构, 普通角闪石应是寄主岩浆贯入结晶的产物.综合上述特征, 可以看出含橄榄石单斜辉石捕虏体为镁铁质岩浆高压堆晶成因.结合华北克拉通东部早白垩世双峰式火山岩组合的出现, 推断含橄榄石单斜辉石岩捕虏体可能是早白垩世基性岩浆底侵的产物.      

徐淮地区镁铁质岩石捕虏体单斜辉石中石榴石和石英的出溶

徐淮地区早侏罗世侵入杂岩中榴辉岩,石榴辉石岩和单斜辉石岩捕虏体单斜辉石中可以观察丰富的出溶石英针和石榴石,黝帘石及角闪石的出溶叶片,榴辉岩中出溶石英针的绿辉石核部比其边部相对富含FeO和MgO,贫SiO2,Al2O3和CaO。在石榴辉石岩和单斜辉石岩捕虏体中具有出溶石榴石的单斜辉石。从靠近出溶石榴石的一侧向其核部,Al2O3,Na2O和TiO2含量降低,MgO,SiO2和CaO含量增加,单斜辉石中定向石英针的出溶表明曾经存在有超高压条件下（≥25×10^8Pa)稳定的过硅质绿辉石。单斜辉石中出溶石榴石表明温压条件的降低可能是引起出溶的一个主要原因,捕虏体中的矿物组合和岩相学特征表明它们曾经遭受了榴辉岩相和角闪岩相退化变质作用,这与因压力和温度降低引起矿物出溶的结果相吻合。     

北苏鲁荣成地区超高压变质带大理岩中石榴辉石岩的退变质过程

北苏鲁荣成地区超高压变质带大理岩中的退变质石榴辉石岩包裹体具有“核-幔-边”结构,核部主要由石榴子石与单斜辉石组成,幔部含有由细小角闪石与绿帘石组成的后成合晶以及颗粒较大的角闪石与单斜辉石,通过详细的岩相学分析以及矿物成分分析,认为这些后成合晶是由石榴子石、单斜辉石以及来自围岩的流体共同反应而产生,大颗粒的角闪石主要是由辉石转变而来的,在幔部这个转变并不彻底,仍有一些残余辉石颗粒。边部主要由角闪石和绿帘石组成。该石榴辉石岩曾经历榴辉岩相超高压变质阶段。没有柯石英超高压代表性矿物（采样处的其他类型岩石都含有柯石英）的原因是石榴辉石岩的原岩为超基性岩。     

大别山双河超高压硬玉石英岩显微组构特征及其流变学意义

硬玉石英岩是大别—苏鲁超高压(UHP) 变质带内重要超高压岩石类型之一, 其变形机制和动力学背景参数(应变、应力、应变速率) 对于全面了解超高压造山带的形成和演化有非常重要的意义.对大别山双河地区超高压硬玉石英岩3个样品中的主要组成矿物硬玉和石英进行显微组构和透射电镜(TEM) 的初步研究.晶格优选方位(LPO) 测量成果表明: 硬玉组构类型与绿辉石相近, 为L, LS型; 石英组构类型主要为单斜对称.TEM研究表明硬玉滑移系以(100) [001]、(110)[001]及(110)1/2[110]为主.石英中位错发育, 滑移系以(0001)[1120]底面滑移为主, 代表硬玉石英岩折返过程中经历的区域性剪切作用      

中亚造山带东部非典型辉绿结构辉绿岩的岩相学特征及鉴定

在中亚造山带东部构造带中发现角闪变质辉绿岩,岩相学特征表明具非典型辉绿结构,显示变余辉绿结构及变余嵌晶含长结构.主要矿物为斜长石及角闪石,次要矿物为单斜辉石和阳起石.全岩岩石化学分析结果：SiO₂含量为49.15%～52.96%、Na₂O+K₂O含量为2.71%～5.07%、CaO含量为7.07%～10.40%、Al₂O₃含量为14.77%～17.31%、TFe0含量为8.80%～12.27%、MgO含量为6.45%～9.57%;在火山岩TAS分类图落入玄武岩区,属于基性岩范围;说明研究区具有非典型辉绿结构的岩石命名为角闪变质辉绿岩的正确性.角闪变质辉绿岩经历了退变质作用：基性斜长石（拉长石）退变质为中性斜长石（中长石）,进一步退变质为钠长石或钠更长石;单斜辉石退变质为角闪石,角闪石退变质为阳起石.     

绢石与顽火辉石光性方位的关系

超基性岩的主要造岩矿物橄榄石及顽火辉石新鲜者极少,大多数分别蚀变为蛇纹石及绢石,这对超基性岩原生构造与组构的研究带来很大困难。几年来,我们在工作中注意了绢石与顽火辉石光性方位的研究。顽火辉石属于斜方晶系,二轴晶正光性,2V=60-80°,a//Nm、b//Np、c//Ng,即[100]//Nm、[010]//Np、[001]//Ng,光轴面//(100)。绢石是顽火辉石的蚀变矿物,已为许多研究者所公认,     

北大别罗田榴辉岩的减压出溶结构与超高压变质作用

岩石学研究表明北大别罗田榴辉岩经过了榴辉岩相、麻粒岩相和角闪岩相变质作用,表现出多种减压出溶结构.特征性的减压出溶结构有单斜辉石和石榴石中分别发育石英+角闪石+斜长石等与金红石+单斜辉石+角闪石等针状矿物出溶体,以及锆石中含有柯石英残晶.这些进一步证明北大别南部（罗田一带）同北部（如黄尾河、百丈岩等地）榴辉岩一样经过了>5～7CPa的超高压变质作用.     

大别山超高压变质岩的显微构造与有效黏度

超高压变质岩提供了研究大陆俯冲隧道中岩石的变形机制和流变差异性的窗口。文章使用电子背散射衍射技术分析了大别山超高压变质带的榴辉岩和长英质片麻岩的显微构造。榴辉岩中的石榴子石基本呈无序分布，绿辉石发育较强烈的晶格优选定向，[001]轴的极密平行或近平行于拉伸线理，(100)面的法线近垂直于面理，退变榴辉岩中角闪石的(100)[001]组构可能继承了绿辉石的晶格优选定向。退变榴辉岩和长英质片麻岩中的石英记录了(0001)低温底面滑移和{1010}中温 柱面滑移，反映了超高压变质岩折返到中地壳的韧性变形；而斜长石的(001)<110>和(010)[100]组构形成于折返到下地壳的角闪岩相变质条件（>600℃）。根据主要矿物的流变律计算了俯冲与折返过程中无水矿物的有效黏度变化。俯冲过程中，钠长石=硬玉+石英的分解反应以及石英-柯石英相变导致长英质片麻岩的有效黏度和密度都显著增高，有利于陆壳深俯冲。但是折返过程中由于温度较高，这两个反应带来的有效黏度变化较小。>80 km深度，石榴子石的流变强度>硬玉>绿辉 石>柯石英，俯冲上地壳的流变由柯石英和硬玉控制，下地壳的流变由绿辉石和石榴子石控制。超高压变质岩流变强度的差异有助于上—下地壳力学解耦，使相对低密度、低黏度的上地壳物质在俯冲隧道内快速折返。     

徐淮早白垩世埃达克质岩中含橄榄石单斜辉石岩的成因及其岩石学意义

报道了徐淮地区早白垩世埃达克质岩中首次发现的含橄榄石单斜辉石岩捕虏体的岩相学与矿物化学资料,该类捕虏体显示堆积结构、块状构造,主要由单斜辉石(~80%)、斜方辉石(~5%)、橄榄石(~5%)和普通角闪石(~10%)组成.橄榄石外侧发育有斜方辉石反应边,角闪石沿辉石粒间分布,呈嵌晶结构.矿物化学分析结果表明:橄榄石的镁橄榄石分子值(Fo)=77.7~79.3,Ni=623×10-6~773×10-6;斜方辉石的Mg#=75.6~80.2,Cr=161×10-6~684×10-6,Ni=79×10-6~708×10-6;单斜辉石的Mg#=84.5~86.4,CaO=21.59%~23.13%,Al2O3=1.72%~2.44%.上述矿物与中、新生代玄武岩中橄榄石、斜方辉石和单斜辉石斑晶以及堆积成因辉石岩中的斜方辉石和单斜辉石成分类似.此外,单斜辉石的稀土配分型式以相对富含中稀土元素的上凸型为特征,稀土元素含量较低(∑REE=10.14×10-6~12.71×10-6),无明显的铕异常(δEu=0.90~1.16),类似于新生代玄武岩中单斜辉石斑晶.捕虏体中的普通角闪石的Mg#=74.0~80.4、SiO2=43.2%~44.5%、Na2O=2.04%~2.29%,稀土元素分馏不明显,显示亏损高场强元素(HFSEs,如Nb、Ta、Zr、Hf),富集Sr、Rb、Ba的特征,与新生代玄武岩中角闪石捕虏晶成分不同.结合其嵌晶结构,普通角闪石应是寄主岩浆贯入结晶的产物.综合上述特征,可以看出含橄榄石单斜辉石捕虏体为镁铁质岩浆高压堆晶成因.结合华北克拉通东部早白垩世双峰式火山岩组合的出现,推断含橄榄石单斜辉石岩捕虏体可能是早白垩世基性岩浆底侵的产物.     

Raman Spectrum Study on Quartz Exsolution in Omphacite of Eclogite and Its Tectonic Significances

The studies on ultra-microstructue characteristics of quartz exsolution in eclogite and coesite in UHP eclogite of several localities are done with the appliance of laser Raman spectroscopy and Ustage. Research results show that the phase transformation of coesite-quartz in garnet and/or omphacite is a continuous process. Topological relationship is present between quartz exsolution in omphacite and its host mineral which shows orientations of two long axes of quartz exsolution parallel to (100) and (-101) of omphacite. At present, some scholars suggest that thequartz exsolution in omphacite of eclogite is the evidence of UHP metamorphism. However, temperature and pressure condition and the exsolution mechanism of oriented needlelike quartz in omphacite still remain undear. Tnerefore, further study should be enhanced on experimental research on exsolution mechanism of super-silicate clinopyroxene, which could provide experimental quantitative constraint on quartz exsolution as UHP indicator.     

榴辉岩中石英出溶体的拉曼光谱学研究及其构造意义

利用拉曼光谱学和费氏台方法对若干地区超高压榴辉岩中柯石英和榴辉岩中石英出溶体的超显微构造特征进行了研究.研究结果表明, 石榴石(或绿辉石) 中柯石英向石英相变是一个连续变化过程.绿辉石中石英出溶体和主晶具有一定的晶体学拓扑关系, 即石英出溶体长轴有两个展布方向: 平行于绿辉石(10 0) 裂理面和平行于绿辉石(- 10 1) 面.目前, 部分学者推断榴辉岩绿辉石中石英出溶体可作为超高压变质作用的标志.笔者认为, 棒状定向石英在绿辉石中出溶的温压条件和出溶机理尚未查明.因此, 需加强过量二氧化硅单斜辉石出溶机理的超高压实验研究, 从而为证实石英出溶体作为超高压标志提供实验定量约束.      

An AEM study of garnet clinopyroxenite from the Sulu ultrahigh-pressure terrane: formation mechanisms of oriented ilmenite,spinel, magnetite,amphibole and garnet inclusions in clinopyroxene

Optical microscopy, secondary electron microscopy and analytical electron microscopy were used to characterize crystallographic orientation relationships between oriented mineral inclusions and clinopyroxene (Cpx) host from the Hujialing garnet clinopyroxenite within the Sulu ultrahigh-pressure (UHP) terrane, eastern China. One garnet clinopyroxenite sample (2HJ-2C) and one megacrystic garnet-bearing garnet clinopyroxenite (RZ-11D) were studied. Porphyroblastic clinopyroxene from sample 2HJ-2C contains oriented inclusions of ilmenite (Ilm), spinel (Spl), magnetite and garnet, whereas clinopyroxene inclusions within megacrystic garnet from sample RZ-11D contain oriented inclusions of ilmenite and amphibole. Specific crystallographic relationships were observed between ilmenite/spinel plates and host clinopyroxene in sample 2HJ-2C and between ilmenite plates and host clinopyroxene in sample RZ-11D, i.e. [1[`1]00 1\bar{1}00 ]<sub>Ilm</sub>//[0[`1]0 0\bar{1}0 ]_Cpx (0001)_Ilm//(100)_Cpx; and [110]_Spl//[0[`1]0 0\bar{1}0 ]<sub>Cpx</sub> ([`1]11 \bar{1}11 )_Spl//(100)_Cpx. These inclusions are suggested to be primary precipitates via solid-state exsolutions. Most of the needle-like magnetite/spinel inclusions generally occur at the rims or along fractures of clinopyroxene within sample 2HJ-2C. Despite the epitaxial relation with host clinopyroxene, these magnetite/spinel needles would have resulted from fluid/melt infiltrations. Non-epitaxial garnet lamellae in clinopyroxene of sample 2HJ-2C were formed via fluid infiltration-deposition primarily along (010) and subordinately along (100) partings. Epitaxial amphibole plates (with a thickness <1 μm) and lamellae (with a thickness = 1–10 μm) in host clinopyroxene of sample RZ-11D were probably results of hydration processes, although amphibole plates could otherwise be interpreted as exsolution products. Temporal relations between mineral inclusions in each sample can be established, and a semi-quantitative P–T path for this garnet clinopyroxenite body was derived accordingly. The present results show that the Hujialing garnet clinopyroxenite may not have subducted to mantle depths as deep as 250 km during UHP metamorphism as suggested by previous studies. This study demonstrates that the crystallographic and temporal/spatial relationships between aligned inclusions and host minerals are essential to a correct genetic interpretation of metamorphic rocks.     

Oriented inclusions of pyroxene,amphibole and rutile in garnet from the Lüliangshan garnet peridotite massif,North Qaidam UHPM belt,NW China: an electron backscatter diffraction study

Oriented inclusions of clinopyroxene, orthopyroxene, sodic amphibole and rutile have been identified in garnet from the Lüliangshan garnet peridotite massif in the North Qaidam ultrahigh‐pressure metamorphic (UHPM) belt, northern Tibetan Plateau, NW China. Electron backscatter diffraction (EBSD) analyses demonstrate that nearly half of the measured intracrystalline clinopyroxene (8 out of 17) have topotactic crystallographic relationships with host garnet, that is, (100)_Cpx//{112}_Grt, (010)_Cpx//{110}_Grt and [001]_Cpx//<111>_Grt. One‐fifth of the oriented sodic amphibole (23 out of 110) inclusions of have topotactic crystallographic relationships with host garnet, that is, (010)_Amp//{112}_Grt, (100)_Amp//{110}_Grt and [001]_Amp//<111>_Grt. Over a third of rutile (36 out of 99) inclusions also show a close crystallographic orientation relationship with host garnet in that one <103>_Rt and one <110>_Rt parallel to two <111>_Grt while the axes of [001]_Rt exhibit small girdles centred the axes of <111>_Grt. But, no ‘well‐fit’ crystallographic relationship was observed between orthopyroxene inclusions and host garnet. Considering a very long and complex history for the Lüliangshan garnet peridotite, we suggest that the low fit rates for these oriented minerals may result from several possible assumptions including different generations or multi‐stage formation mechanisms, heterogeneous nucleation and growth under non‐equilibrium conditions, and partial changes of initial crystallographic orientations of some inclusions. However, the residual quantitative ‘well‐fit’ crystallographic information is sufficient to indicate that the nucleation and growth of many pyroxene, amphibole and rutile are controlled by the lattice of the host garnet. The revealed close topotactic relationships accompanied by clear shape orientations provide quantitative microstructural evidence demonstrating a most likely exsolution/precipitate origin for at least some of the oriented phases of pyroxene, sodic amphibole and rutile from former majoritic garnet and support an ultra‐deep (>180 km depth) origin of the Lüliangshan garnet massif.     

Ca-Eskola incorporation in clinopyroxene: limitations and petrological implications for eclogites and related rocks

Clinopyroxene is an essential mineral in eclogitic rocks. It commonly contains minor amounts of the defect-bearing Ca-Eskola (CaEs, Ca_0.5□_0.5AlSi₂O₆) component, with higher concentrations generally considered to indicate a high-pressure origin at least within the coesite stability field. Changes in pressure and temperature conditions can lead to exsolution of this component as a free SiO₂ phase, which may have a number of petrological implications. This makes it important to understand the factors that maximize CaEs incorporation in clinopyroxene. We have undertaken a series of experiments at high pressures and temperatures (4–10 GPa and 1000–1350 °C) to further investigate the systematics of CaEs incorporation in eclogite-like clinopyroxene and the factors responsible for maximizing CaEs contents. Two simple chemical systems were chosen that allow unambiguous interpretation of the results: (1) CMAS + H₂O and (2) two compositions in the NCMAS system. All experimental products contained clinopyroxene and garnet along with either a free SiO₂ phase or a silicate melt. Coexisting garnet is grossular-rich, generally with X _gr ≥ 0.67. Compositional variations are attributable to the presence or absence of melt and changes in modal amounts of garnet at different pressure–temperature conditions. Even small amounts of H₂O lower the solidus temperature and the presence of a melt reduces the SiO₂ activity, which destabilizes the CaEs component in clinopyroxene. The CaEs and the Ca-Tschermaks (CaTs, CaAl₂SiO₆) components in clinopyroxene decrease with increasing jadeite mole fraction, which is also a function of pressure and bulk Al content. Modeling X-ray powder diffraction data yields a molar volume for the CaEs endmember of V _CaEs = 60.87(63) cm³, which reasonably agrees with a literature value that was estimated from natural samples. In the presence of coexisting coesite, the CaEs and CaTs do not vary independently of each other, being controlled by the internal equilibrium 2CaEs = CaTs + 3SiO₂ (coesite). This relation, observed in simple systems (i.e., CMAS ± Na), is also obeyed by clinopyroxene in more complex, natural analog bulk compositions. An assessment of available experimental data reveals a maximum of 15–18 mol% CaEs in eclogitic clinopyroxene at conditions corresponding to 130–180 km depth. CaEs contents are maximized at high temperatures; i.e., at or near the solidus in the presence of coesite. Thus, this study supports the role of CaEs exsolution in contributing to melt generation during upwelling of eclogite bodies in the mantle, albeit with some caveats. Somewhat higher maximum CaEs contents (~20 mol%) are found in Ca and Al-rich bulk compositions, such as grospydite xenoliths. Such bulk compositions also seem to require the coexistence of kyanite. Other Ca and Al-rich rock types, like rodingites, should have the potential of containing CaEs-rich clinopyroxenes, except that they are SiO₂-undersaturated. This emphasizes the further role of bulk composition, in addition to high temperatures, in achieving maximum CaEs contents in high-pressure clinopyroxene.     

海南文昌二辉橄榄岩中辉石出溶结构的结晶学取向分析

本文用电子背散射衍射技术(electron backscatter diffraction,EBSD)测试了海南文昌玄武岩中二辉橄榄岩包体中的辉石主晶与其出溶片晶的结晶学取向关系。结合电子探针成分测试,得出:单斜辉石(透辉石)主晶中出溶了两组不同方向的片晶,一组为斜方辉石(顽火辉石-易变辉石)片晶,另一组为单斜辉石(普通辉石)片晶。由于出溶片晶在EBSD测试切面上体现为以线状体,因此需要找到一种方法将线状体所代表的片晶的晶面符号推算出来。本文介绍了一种利用吴氏网进行坐标系旋转的"晶带相交法",该方法可以作图推算出溶片晶的晶面符号。根据"晶带相交法"得出,斜方辉石(顽火辉石-易变辉石)出溶片晶为(100),单斜辉石(普通辉石)出溶片晶为~(401)。根据前人的研究资料,出溶片晶~(401)可能指示最小出溶压力为9.5~12.5GPa。出溶片晶的结晶学取向涉及到主晶与出溶体的晶体结构匹配关系,并且与出溶温度-压力有关,因此出溶片晶的结晶学取向分析具有晶体化学理论意义和反映地质温压过程的实际意义。这种"晶带相交法"可以推广应用于其他矿物出溶结构的结晶学取向研究中。     

Exsolution of Ca-clinopyroxene from orthopyroxene aided by deformation

Monoclinic calcium-poor shear-transformation lamellae and calcium-rich exsolution lamellae occur parallel to (100) in orthopyroxene. The formation of both structures from an orthopyroxene host involves a shear on (100) parallel to [001], with additional cation exchange in the exsolution case. The shear transformation involves a macroscopic simple shear angle of 13.3° (shear strain of 0.236) and produces a specific a-axis orientation with respect to the sense of shear; we have found that this orientation dominates in exsolution lamellae in kinked orthopyroxene, where the sense of shear is known. In undeformed orthopyroxene, there is generally no preferred sense of orientation of the monoclinic a axes. We advance a specific model for exsolution involving nucleation and growth by shear transformation combined with cation exchange, thus circumventing the classical nucleation barrier and permitting exsolution at lower solute supersaturations.     

Superposition of replacements in the mafic granulites of the Jijal complex of the Kohistan arc, northern Pakistan: dehydration and rehydration within deep arc crust

A deep-level crustal section of the Cretaceous Kohistan arc is exposed in the northern part of the Jijal complex. The occurrence of mafic to ultramafic granulite-facies rocks exhibits the nature and metamorphic evolution of the lower crust. Mafic granulites are divided into two rock types: two-pyroxene granulite (orthopyroxene+clinopyroxene+plagioclase±quartz [1]); and garnet–clinopyroxene granulite (garnet+clinopyroxene+plagioclase+quartz [2]). Two-pyroxene granulite occurs in the northeastern part of the Jijal complex as a relict host rock of garnet–clinopyroxene granulite, where the orthopyroxene-rich host is transected by elongated patches and bands of garnet–clinopyroxene granulite. Garnet–clinopyroxene granulite, together with two-pyroxene granulite, has been partly replaced by amphibolite (hornblende±garnet+plagioclase+quartz [3]). The garnet-bearing assemblage [2] is expressed by a compression–dehydration reaction: hornblende+orthopyroxene+plagioclase=garnet+clinopyroxene+quartz+H₂O↑. Subsequent amphibolitization to form the assemblage [3] is expressed by two hydration reactions: garnet+clinopyroxene+plagioclase+H₂O=hornblende+quartz and plagioclase+hornblende+H₂O=zoisite+chlorite+quartz. The mafic granulites include pod- and lens-shaped bodies of ultramafic granulites which consist of garnet hornblendite (garnet+hornblende+clinopyroxene [4]) associated with garnet clinopyroxenite, garnetite, and hornblendite. Field relation and comparisons in modal–chemical compositions between the mafic and ultramafic granulites indicate that the ultramafic granulites were originally intrusive rocks which dissected the protoliths of the mafic granulites and then have been metamorphosed simultaneously with the formation of garnet–clinopyroxene granulite. The results combined with isotopic ages reported elsewhere give the following tectonic constraints: (1) crustal thickening through the development of the Kohistan arc and the subsequent Kohistan–Asia collision caused the high-pressure granulite-facies metamorphism in the Jijal complex; (2) local amphibolitization of the mafic granulites occurred after the collision.