胶东—苏北构造带特征及动力学演化

提出胶东—苏北构造带以广泛出露榴辉岩和超基性岩、普遍发育韧性剪切带和糜棱岩带为特征,具混杂岩特点。它经历了早元古代大陆推覆构造事件(2000～2400Ma)、早元古代末低角闪岩相变质热事件(1800～2000Ma)和元古代末大陆推覆构造事件(6O0～800Ma)。该构造带是华北陆块与华南陆块之间的过渡带。     

安徽张八岭隆起东缘基底走滑韧性剪切带的发现及其构造意义

张八岭隆起位于华南地块与华北地块碰撞拼接的构造转换部位,其西界为著名的郯庐断裂带,东缘属于扬子地块盖层前陆逆冲褶皱构造带。在张八岭隆起东缘来安地区基底变质岩中发现了一条宽达2.5km的走滑韧性剪切带,对其进行了详细的野外测量和岩石学、显微组构、变形运动学分析。结果显示,韧性剪切带由初糜棱岩带、糜棱岩带和超糜棱岩带组成;糜棱岩叶理近直立,叶理面上的拉伸线理向SW缓倾(倾伏角为10～30°);S-C组构和不对称旋转碎斑指示以左旋剪切为主。根据石英位错密度估算的差应力为65～75MPa。糜棱岩矿物成分和显微组构特征分析显示基底韧性剪切带的形成温度在250～400℃之间,形成深度为10～20km。该基底走滑剪切带的发现为张八岭地块的斜向走滑折返机制提供了重要的构造地质学制约。     

青海滩间山金矿床地质特征和控矿因素分析

滩间山金矿床产于中元古界万洞沟群碳质糜棱片岩和华力西晚期侵入岩中。矿床是在热水沉积、区域变质和热变质的预富集基础上,与区域进变质型绿片岩相韧性剪切带的退化演化同步,经历了脆韧性、韧脆性和脆性剪切变形成矿阶段的演化,并遭受华力西晚期侵入岩浆活动相伴的热液成矿作用的叠加改造形成的。不同时期、不同成矿作用的叠加和多种有利因素的结合控制了滩间山金矿床的形成。经生产实践证实,具有形成大型金矿床的多种有利成矿地质条件     

郯庐断裂中段鲁中基底韧性变形带的形成时代

郯庐断裂中段鲁中基底的韧性变形带可分为两类：（１）北东向韧性变形带,以发育中深层次的构造片麻岩为特征,形成于早中元古代花岗质岩体（２４８８Ｍａ）侵位之前;（２）北北东向韧性变形带,以中浅层次糜棱岩为特征,形成于晋宁期（９４１Ｍａ）。文中对以上两类韧性变形带的形成机制和时代进行了初步讨论。     

Late Palaeozoic NE–SW ductile–brittle extension in the La Serre horst,eastern France

In the La Serre horst of the Alpine foreland, the pre-Triassic La Serre median fault zone separates a Late Devonian–Early Carboniferous granite from an ignimbrite of unknown age and from Permian deposits. Motion along this fault zone took place first in ductile conditions and then evolved in brittle conditions. Both ductile and brittle shear criteria indicate a top-NE normal-dextral displacement. Similar motions are reported along faults bounding Late Palaeozoic intramontane coal basins located in the Massif Central and correspond to a widespread NE–SW Late to Post-Orogenic extension that affected the Variscan basement during Late Carboniferous to Early Permian times. To cite this article: G. Coromina, O. Fabbri, C. R. Geoscience 336 (2004).     

越城岭花岗岩体西侧滑脱型韧性剪切带的发现及其形成的构造体制

越城岭花岗岩体西侧片麻状花岗岩带主体是一条由韧性剪切作用形成的复合糜棱岩带,包括早期高绿片岩相条件下形成的糜棱片麻岩和晚期低绿片岩相条件下形成的糜棱岩。高绿片岩相韧性剪切带和低绿片岩相韧性剪切带具有基本一致的运动学性质,为滑脱型韧性剪切带,总体为在向NWW缓倾的糜棱面理上向SW方向滑动,并在平面上表现为左旋效应。根据构造对比研究,认为越城岭西侧滑脱型韧性剪切带形成于后造山阶段的伸展构造体制。     

Growth of myrmekite coronas by contact metamorphism of granitic mylonites in the aureole of Cima di Vila, Eastern Alps, Italy

In the contact aureole of the Oligocene granodiorite of Cima di Vila, granitic pegmatites of Variscan age were strongly deformed during eo‐Alpine regional metamorphism, with local development of ultramylonites. In the ultramylonite matrix, consisting of quartz, plagioclase, muscovite and biotite, microstructures show grain growth of quartz within quartz ribbons, and development of decussate arrangements of mica. These features indicate that dynamic recrystallization related to mylonite development was followed by extensive static growth during contact metamorphism. K‐feldspar porphyroclasts up to 1.5 cm are mantled by myrmekite that forms a continuous corona with thickness of about 1 mm. In both XZ and YZ sections, myrmekite tubules are undeformed, and symmetrically distributed in the corona, and oligoclase‐andesine hosts have random crystallographic orientation. Myrmekite development has been modelled from the P–T–t evolution of the ultramylonites, assuming that the development of the ultramylonites occurred during eo‐Alpine metamorphism at c. 450 °C, 7.5 kbar, followed by contact metamorphism at c. 530 °C, 2.75 kbar. Phase diagram pseudosections calculated from the measured bulk composition of granitic pegmatite protolith indicate that the equilibrium assemblage changes from Qtz–Phe–Ab ± Zo ± Cpx ± Kfs during the ultramylonite stage to Qtz–Pl(An_30–40)–Ms–Kfs–Bt(Ann₅₅) during the contact metamorphic stage. The thermodynamic prediction of increasing plagioclase mode and anorthite content, change of white mica composition and growth of biotite, occurring during the end of the heating path, are in agreement with the observed microstructures and analysed phase compositions of ultramylonites. Along with microstructural evidence, this supports the model that K‐feldspar replacement by myrmekite took place under static conditions, and was coeval with the static growth accompanying contact metamorphism. Myrmekite associated with muscovite can develop under prograde (up‐temperature) conditions in granites involved in polymetamorphism.     

松辽盆地西缘断裂带中花岗质糜棱岩的锆石SHRIMP和云母氩-氩年龄及其构造意义

松辽盆地西缘发育大型的北北东走向韧性断裂带,该韧性断裂带的性质、活动时限一直存在争议,制约了对松辽盆地构造成因的认识以及松辽盆地西缘油气勘探开发的进展。腾克、金星及嘎拉山地区是松辽盆地西缘韧性断裂带的代表性出露区,主体岩石组合为条带状花岗质糜棱岩、眼球状花岗质糜棱岩等。腾克、金星及嘎拉山地区发育一组糜棱面理和线理,其中面理为110°~135°∠45°~65°、线理为倾伏向10°~25°,倾伏角10°~35°;其运动性质均显示左行走滑特征。确定韧性断裂带活动时限的样品采自构造带内花岗质糜棱岩的锆石和同变形云母,其中锆石SHRIMP谐和年龄为296.9~299.4 Ma;黑云母⁴⁰Ar-³⁹Ar年龄为(123.0±0.7)Ma,白云母的⁴⁰Ar-³⁹Ar年龄为(124.4±0.9)Ma。松辽盆地西缘韧性断裂带应该属于嫩江断裂带的北段。年龄结果表明该韧性断裂带中花岗岩侵位于晚石炭世,大型北北东向韧性构造变形发生于早白垩世。腾克金星嘎拉山剪切带控制松辽盆地西缘,同时表明松辽盆地在早白垩世经历了走滑挤压盆地演化阶段,这种大型北北东向韧性断裂带的形成可能与当时西太平洋伊泽纳崎板块向欧亚大陆俯冲发生转向有关。     

苏鲁造山带南缘虎山多期次韧性剪切变形特征研究

从变形机制、力学性质和变质变形矿物世代研究入手,对江苏东北部苏鲁造山带南缘东海虎山多期叠加剪切带进行的研究表明,该区存在三期韧性剪切变形,第一期为滑脱拆离变形,长英质糜棱岩中形成长石拉伸线理,榴辉岩中形成绿辉石、石榴石分异成分层;第二期变形为韧性逆冲,形成蓝晶石、多硅白云母、黝帘石拉伸线理,在榴辉岩中形成石榴石眼球体;第三期变形为韧脆性逆冲构造,形成长英质S—C糜棱岩,具S—C面理和丝带状石英条带,该结论为建立区域构造变形序列提供了依据。     

辽宁红透山块状硫化物矿床矿石糜棱岩铜-金富集机制

辽宁红透山太古宙块状硫化物型铜锌矿床成矿后的变质作用达到高角闪岩相 ,并经历了 3个阶段的变形。矿床的主要矿石矿物为黄铁矿、磁黄铁矿、黄铜矿和闪锌矿。主矿体内分布有 30多条矿石糜棱岩带 ,它们大多数平行或近于平行块状硫化物矿层 ,少数产在矿体附近围岩中。带中的各种硫化物矿物均遭受了强烈的剪切变形 ,其中黄铁矿以碎裂为主 ,而磁黄铁矿、黄铜矿和闪锌矿显示强烈的塑性。矿石糜棱岩比块状硫化物矿石明显富集铜、金、银等元素 ,其铜、金和银平均含量分别达1 1 .0 0 % ,1 .74g/t和 2 35g/t,相对于块状矿石的富集系数分别为 5 .3、5 .0和 4 .6。这些金属的高度富集主要是因为矿石糜棱岩受到了后期流体的叠加。铅同位素组成表明矿石糜棱岩中的金属一部分来自块状矿石 ,另一部分来自块状硫化物矿体之外。韧性剪切和流体叠加均发生于矿床退变质过程中