阴山地区早前寒武纪岩石构造分区及古元古地壳碰撞—伸展构造机制

阴山地区从东南到西北，依次划分为桑干麻粒岩区，集宁副变质岩区，乌拉山－大青山前缘绝构造区和色尔腾山岛弧过渡区。桑干麻粒岩区代表了中太古微古陆并经新太古强烈岩 增生的太古地壳；集宁区代表基底之上新太古末期－古元古沉积盖层；乌拉山－大青山区是基底岩石构造剥露的前构造区；     

横贯阴山地区早前寒武纪岩石温度压力、PTt轨迹及地壳演化意义

横贯阴山地区峰值温度压力等值线和岩性一构造特点将该区分为4个不同温度—压力—岩性—构造区,即桑干麻粒岩区、集宁副变质岩区、乌拉山 大青山前缘构造区和色尔腾山区。阴山地区经历了新太古代(2.5Ga±)和古元古代(1.9G±)两期重要的构造热事件。色尔腾山区新太古代 P-T轨迹为顺时针,压力由>1500MPa到1000～2000MPa,显示着岛弧环境。桑干区新太古代P-T轨迹为反时针P-T轨迹,为中太古代微古陆岩浆板底垫托特点。古元古代时期两个太古宙古陆(岛弧)碰撞,乌拉山到桑干区太古宙基底向北逆冲抬升,P-T轨迹由1000～1200MPa到500～700MPa降压过程。南部集宁区     

阴山地区前寒武纪变质岩石地层序列

作者等从１９９０年开始，在研究阴山地区前寒武纪变质岩群年代构造格架过程中，采用“构造－地（岩）层－事件法”和变质岩构造解析的方法，对阴山地区前寒琥系重新进行了厘定，采用单颗粒锆石Ｕ－Ｐｂ，Ｓｍ－Ｎｄ等时线同位素测年方法对各岩群进行了测定，初步建立了阴山地区的前寒武纪变质岩群的年代构造格架，将阴山地区前寒武纪岩石地层序列划分为；中太古代兴和岩群，晚太古代集宁群／乌拉山岩群，色尔腾山群，古元古代层侵纪     

华北克拉通北缘内蒙古达茂旗地区前寒武纪基底岩石组合及形成时代

在华北克拉通北缘达茂旗地区,近东西向分布前寒武纪基底,前人根据岩石组合特征将其划为色尔腾山岩群,但缺乏年代学依据.通过岩石学、LA-ICP-MS锆石U-Pb年龄及其微量元素地球化学、锆石Lu-Hf同位素等研究对达茂旗地区前寒武纪基底岩石组合、形成时代、物质来源进行讨论.研究表明,达茂旗地区前寒武纪基底由色尔腾山岩群和古...     

冀北高压麻粒岩带岩石组合性质、同位素特征及其演化

通过对冀北高压麻粒岩带中各岩石单元岩石组合和同位素年代学研究，划分出北部红旗营子表壳岩带、中部高压麻粒岩带和南部单塔子－桑干杂岩带三个构造岩石单元，进而对中部高压麻粒岩带划分出南北两个亚带。南部亚带主要为2500Ma的钾长花岗岩、高压麻粒岩和再造的单塔子－桑干杂岩；北部亚带由2000－1800Ma的花岗岩带、红旗营子群岩片组成。推断本区高压麻粒岩带实际是新太古代和古元古代两次超大陆汇聚事件的产物。     

赣中变质基底Nd模式年龄初步研究及基底地壳的形成时代

本文研究了赣东南变质基底的Ｎｄ模式年龄（ＴＤＭ＝１３６０－２１２４Ｍａ,平均为１７５５Ｍａ）,结合变质岩的Ｒｂ－Ｓｒ,Ｓｍ－Ｎｄ等时线年龄确认赣中地区存在前寒武纪地壳基底,推测本区还有一个尚未出露的古元古－新太古代的花岗质陆壳,这个陆壳正是元古代的陆源区     

赣中变质基度Nd模式年龄初步研究及基底地壳的形成时代

本文研究了赣东南变质基底的Ｎｄ模式年龄（ＴＤＭ＝１３６０－２１２４Ｍａ,平均为１７５５Ｍａ）,结合变质岩的Ｒｂ－Ｓｒ,Ｓｍ－Ｎｄ等时线年龄确认赣中地区存在前寒武纪地壳基底,推测本区还有一个尚未出露的古元古－新太古代的花岗质陆壳,这个陆壳正是元古代的陆源区。     

甘肃敦煌-北山早前寒武纪岩石组合-构造初步框架

甘肃敦煌－北山地区广泛出露早前寒武纪岩石。这些岩石在早期的《甘肃省区域地质志》中被确定为前长城系、长城系、奥陶－志留系及部分石炭系。本文认为这些岩石应属太古宙和古元古代。据此，重新厘定了该区早前寒式纪岩石－构造框架。自南向北划分为敦煌太古宙杂岩区、北山南带古元古代剪切构造区和北山北带古元古代－太古宙杂岩区，并根据变形特点和岩石组合，进一步划分出次级带。     

甘肃敦煌—北山早前寒武纪岩石组合—构造初步框架

甘肃敦煌－北山地区广泛出露早前寒武纪岩石。这些岩石在早期的《甘肃省区域地质志》中被确定为前长城系、长城系、奥陶－志留系及部分石炭系。本文认为这些岩石应属太古宙和古元古代。据此，重新厘定了该区早前寒武纪岩石－构造框架。自南向北划分为敦煌太古宙杂岩区、北山南带古元古代剪切构造区和北山北带古元古代－太古宙杂岩区，并根据变形特点和岩石组合，进一步划分出次级带。     

内蒙古狼山西段色尔腾山岩群地球化学特征及构造环境判别

狼山地区色尔腾山岩群的研究对探讨华北板块北缘西段晚太古代的构造演化及指导该区铁、铜等矿产勘查具有重要意义。通过对尚德—明路一带色尔腾山岩群的地球化学特征及构造环境研究发现,研究区色尔腾山岩群岩石中富钠贫钾,轻稀土富集,Eu略微亏损;总体富集微量元素;原岩建造为泥质碎屑岩—中基性火山岩和碳酸盐岩建造特点,形成环境为滨海相—浅海相,伴随有小规模的岛弧型火山喷发,晚太古代古蒙古洋开始闭合;同时较厚的碳酸盐岩的沉积说明尚德—明路一带海水较深,不利于含铁、铜的物质沉积。     

晋冀内蒙交界区下地壳流变性质的实验研究及其构造演化意义

酸性和基性麻粒岩的高温度压实验表明,基稳态流动律分别为：ε＝２０．７ｅｘｐ（－２８８／ＲＴ）·Δσ＾３．０和ε＝１０＾６．５９ｅｘｐ（－４２５／ＲＴ）·Δσ＾３．０２,并可与加拿大地盾的麻粒岩流动津相比。在下地壳的温度７００℃-１０００℃、压力１．０Ｇｐａ-１．２ＧＰａ和应变率１０＾－４／ｓ￣１０＾－７／ｓ条件下,岩石变形以韧性变形为主,并发育韧性剪切带,其中辉石和斜长石极易发生动态重结晶及定向排成线理,石英则巳静态恢复,此结果与野外观察的吻合。下地壳的宏观流变模型显示,增厚型下地壳存在一厚的低蠕变强度层,减薄型地壳则上地壳也出现低强度层,太陆下地壳这种低蠕变强度层的流变性质有助于岩石圈增厚和减薄的发生。     

Dehydration melting, fluid buffering and decompressional P–T path in a granulite complex from the Eastern Ghats, India

A suite of metapelites, charnockites, calc-silicate rocks, quartzo-feldspathic gneisses and mafic granulites is exposed at Garbham, a part of the Eastern Ghats granulite belt of India. Reaction textures and mineral compositional data have been used to determine the P–T–X evolutionary history of the granulites. In metapelites and charnockites, dehydration melting reactions involving biotite produced quartzofeldspathic segregations during peak metamorphism. However, migration of melt from the site of generation was limited. Subsequent to peak metamorphism at c . 860° C and 8 kbar, the complex evolved through nearly isothermal decompression to 530–650° C and 4–5 kbar. During this phase, coronal garnet grew in the calc-silicates, while garnet in the presence of quartz broke down in charnockite and mafic granulite. Fluid activities during metamorphism were internally buffered in different lithologies in the presence of a melt phase. The P–T path of the granulites at Garbham contrasts sharply with the other parts of the Eastern Ghats granulite belt where the rocks show dominantly near-isobaric cooling subsequent to peak metamorphism.     

德兴铜矿、银山铜铅锌矿床的岩浆岩岩石化学特征及其成岩成矿机理探讨

德兴斑岩铜矿和银山铜铅锌矿床位于江南古陆与钱塘坳陷之过渡带,赣东北深大断裂的北西盘。德兴斑岩铜矿与燕山期(169Ma)浅成花岗闪长斑岩侵入体具有成因联系,侵入体属低硅钠质组合,铝质参数A[A=Al-(K+Na+2Ca)]值变化于-13—93,表现为铝次饱和到不饱和特征,镁铁质参数B(B=Fe+Mg+Ti)值变化于100—265,二者构成负斜率岩浆演变趋势线,表明岩浆起源于上地幔或下地壳。银山矿床的形成与燕山期(145—142Ma)陆相火山一次火山岩系有关,其属高硅钾质火山岩组合,铝质参数A值变化于7—17     

Origin of Mg-Metatholeiites of the Schirmacher Region,East Antarctica: Constraints from Trace Elements and Nd-Sr Isotopic Systematics

The mafic granulites of Schirmacher region, East Antarctica, the rocks under study, occur more or less as concordant sills or as lenses or as boudinage structures within the felsic rocks, charnockites or metapelites of the region. They show variation from garnet bearing two-pyroxene granulites and garnet free pyroxene granulites to transitional amphibolite-pyroxene granulites. Their major, trace, REE and isotopic chemistry are not distinct from each other and they represent Mg-basalts with MgO >7% and Al₂O₃ <16%.The majority of the analyzed samples plot in the tholeiitic field or show tholeiitic trends, suggesting their metatholeiitic nature as well as general preservation of original composition. The rocks are characterized by enriched large-ion lithophile elemental concentrations than that of mid-oceanic ridge basalts. Their high-field strength elements and heavy rare-earth elemental concentrations, however, are as that of mid-oceanic ridge basalts, a feature which is also reflected in the ratios of their large-ion lithophile elements against high-field strength elements and heavy rare-earth elements, wherein we find these ratios are higher than N-type MORB. Further, the rocks show negative Nb anomaly, high Th/Ta ratio and low La/Nb ratio, which are also characteristics of subduction-related magmatism.The isotopic studies carried out on these samples show that, the Sm-Nd and Rb-Sr dating did not yield much spread, but suggested a Sm-Nd metamorphic age of ∼960 Ma. Rb-Sr dating gave ages ∼886 Ma, suggesting the reworking of the Rb and Sr elements during subsequent tectonothermal overprinting. The Nd model ages (T_DM^Nd) of these rocks show a relatively restricted range of 1120 to 1357 Ma, suggesting mafic magmatism ∼1200 Ma. The positive eNd values (+4.22 to +6.07) shown by these rocks, represent a juvenile crustal fragment derived from melting of mantle precursors, without significant reworking of older crustal material. It is proposed that these rocks were produced by partial melting of a mantle source, characterized by LILE enrichment, related principally to dehydration of subducted oceanic crust.     

High-pressure granulite facies metamorphism in the Pan-African belt of eastern Tanzania: P–T–t evidence against granulite formation by continent collision

To constrain the tectonic history of the Pan-African belt in Tanzania, we have studied the P–T evolution of granulites from northern and eastern Tanzania representative for a large part of the southern Pan-African belt of East Africa (e.g. Pare, Usambara, Ukaguru and Uluguru Mountains). Thermobarometry (conventional and multireaction equilibria) on enderbites and metapelites gives 9.5–11 kbar and 810±40 °C during peak metamorphism at 650–620 Ma. This is consistent with the occurrence of both sillimanite and kyanite in metapelites and of the high-P granulite facies assemblage garnet–clinopyroxene–quartz in mafic rocks. Peak metamorphic conditions are surprisingly similar over a very large area with N-S and E-W extents of about 700 and 200 km respectively. The prograde metamorphic evolution in the entire area started in the kyanite field but evolved mainly within the sillimanite stability field. The retrograde P–T evolution is characterized by late-stage kyanite in metapelites and garnet–clinopyroxene coronas around orthopyroxene in meta-igneous rocks. This is in agreement with thermobarometric results and isotopic dating, indicating a period of nearly isobaric and slow cooling prior to tectonic uplift. The anticlockwise P–T path could have resulted from magmatic underplating and loading of the lower continental crust which caused heating and thickening of the crust. Substantial postmetamorphic crustal thickening of yet unknown age (presumably after 550 Ma) led subsequently to the exhumation of high-P granulites over a large area. The results are consistent with formation of the Pan-African granulites at an active continental margin where tonalitic intrusions caused crustal growth and heating 70–100 Ma prior to continental collision. The P–T–t path contradicts recent geodynamic models which proposed tectonic crustal thickening due to continental collision between East and West Gondwana as the cause of granulite formation in the southern part of the Pan-African belt.     

内蒙古大青山高级变质岩中熔体线理特征

熔体线理由浅色部分熔融物质形成长的集合体或杆状体沿着应变椭球体X轴方向定向排列构成,是高级变质岩特有的一种线状构造.熔体线理发育在深部构造层次韧性变形带中,与矿物拉伸线理一样具有运动方向指向意义.熔体线理形成于伸展构造环境中,是变形作用、变质作用和部分熔融作用共同作用的结果.伸展构造变形导致岩石部分熔融,是熔体线理形成...     

An example of structural and metamorphic relationships in the Musgrave orogenic belt,central Australia

The western Musgrave Ranges are broadly divided into three groups of metamorphic rocks. A central granulite‐facies core is bounded on the north by rocks of amphibolite grade and on the south by rocks transitional between the granulite and amphibolite facies. Faults trending east‐west separate the three groups of rocks.

The detailed structural relationships between the granulites and the lower grade rocks are described and discussed. The granulites are structurally relatively simple and are characterised by the presence of a strong southwesterly‐plunging, mineral‐streaking lineation. In marked contrast, the transitional rocks are more complexly folded on a macroscopic scale and they also have a well‐developed mineral lineation plunging to the southeast. These two lineation orientations are considered to be directions of maximum elongation. The amphibolite‐facies rocks are also complexly folded and at least two lineations related to different phases of deformation have been recognized.

A suite of foliated and lineated dolerite dykes which occurs throughout the area inherited their fabric during a period of intense deformation and recrystallization, which resulted in the development of numerous mylonite zones.

It is suggested that the granulite‐facies rocks may represent a suite of cover rocks which have been thrust in a northerly direction over a pre‐existing amphibolite‐facies basement.     

相山、银山、紫金山次英安玢岩的比较研究

相山、银山、紫金山矿田（床）的次英安玢岩虽然出露形态不尽相同，但都是火山岩浆旋回晚期的产物，CA＞56，δ＜3．3，稀土配分曲线较相似，具有地幔组分和地壳组分高度混合的源区特征，反映它们都是与斑岩铜矿有关的钙碱性次火山岩。根据银山、紫金山矿（床）田的矿化分带和相山矿田剥蚀不深的事实，推测相山矿田或火山机构中心地带的深部，有大规模Cu多金属矿化分布。     

Geochemistry and isotope (Sr, Nd, O) study of Al–Mg granulites from the In Ouzzal Archaean block (Hoggar, Algeria)

The In Ouzzal Al–Mg granulites are found within sedimentary units deposited after 2.7 Ga, the whole association being metamorphosed under extreme temperature conditions (c. 1000 °C) at 2 Ga. The Al–Mg granulites are interlayered with other metasediments, including metapelites, quartzites and magnetite-bearing quartzites, forsterite-spinel marbles, and a few meta-igneous rocks (mainly pyroxenites). They do not occur at a specific position in the sedimentary suite, and they do not reflect any particular structural control. The major and trace element compositions of Al–Mg granulites (especially the high Cr, Ni, Co contents) show that their peculiar ‘refractory’ chemistry is more compatible with premetamorphic sedimentary characteristics rather than with metasomatic, metamorphic or partial melting processes. Sedimentary admixtures of a common mature detrital component coming from the weathering of the local acidic igneous crustal protoliths (normal pelitic component) with an extremely immature component derived from reworking of basic/ultrabasic lithologies (Al–Mg–Cr–Co–Ni–rich chloritic component) is consistent with the geochemistry of such rocks. As in other instances, the quartz-garnet oxygen isotopic thermometer here records an apparent temperature close to the peak metamorphism (c. 1000 °C). Although the persistence of pre-existing δ¹⁸O variations on a small scale during the metamorphism does not support a major pervasive fluid flow during metamorphism, it does not rule out the presence of syn- to post-metamorphic CO₂. The low δ¹⁸O (c.+ 5 to + 6‰) of the most typical Al–Mg granulites indicate that the ‘chloritic component’ in these rocks was derived from hydrothermally altered mafic/ultramafic protoliths rather than dominantly from palaeosols. It is suggested that the presence of such Al–Mg–Cr–Co–Ni–rich sediments is indirect evidence for the presence of greenstone belts in the local crust of the In Ouzzal at 2.6–2.7 Ga.     

江西银山金、铜多金属矿床构造动力-火山岩浆同步一体成矿热结构模式

银山金铜多金属矿床位于赣东北深断裂的北西侧。矿区大面积出露前震旦系双桥山群浅变质岩,其上有零星不整合产出的上侏罗统鹅湖岭组火山碎屑岩—熔岩。矿区褶皱构造主体为双桥山群浅变质岩构成的银山背斜,沿背斜轴部发育一条斜贯全区的剪切带。区内主要发育燕山早期的火山碎屑岩、熔岩、次火山岩及隐爆角砾岩。大量事实表明,该矿床经历了构造动力热液成矿和火山－岩浆热液成矿,两种成矿作用在时间上具同期性,在空间上两者密切相关,构成了构造动力—火山岩浆同步一体的成矿体系。