东大别山北缘姚河岩体与边部糜棱岩带的研究及其地质意义

位于东大别山北缘的姚河岩体是最近确定的中侏罗世石英二长岩体,角闪石４０Ａｒ ３９Ａｒ法定年为１５５．８Ｍａ,用角闪石压力计法得出结晶压力为（２．６５±０．５）×１０２ＭＰａ,结晶定位深度约９ｋｍ。岩体北缘发育的ＮＥ倾的糜棱岩带是磨子潭 晓天断裂韧性剪切的结果。对剪切带中宏观标志及显微、超显微构造研究表明,该断裂自中侏罗世之后主要表现为上盘向ＮＥ方向下滑的正断层,两盘垂直差异隆升达９ｋｍ。结合区域构造及深部资料分析显示,东大别造山带并不具有“翻花状”双侧造山链特点     

郯庐断裂带南段韧性剪切带糜棱岩化过程中长石成分和结构状态变化特征的研究

在对郯庐断裂带南段３条韧性剪切带中糜棱岩及围岩进行矿物组合、结构构造观察研究的基础上,对长石矿物进行了多项分析测试,发现长石成分及其结构状态参数的变化与构造应力场的构造作用存在明显的对应关系：随剪切变形作用的加强,长石矿物的结构状态参数呈增大趋势,矿物单位晶胞的体积和斜长石中Ｓｉ／Ａｌ比值随之减小;长石的变形指数（Ｉｓｓ）和斜长石中的钙长石分子（Ａｎ）与岩石的变形强度呈明显的正相关关系。这些研究结果为探讨构造变形场中矿物岩石的变形 变质作用提供了一种简捷有效的手段     

浙西南八都群变火山岩及变晶糜棱岩的同位素年龄及其构造意义

浙西南八都群变火山岩系的Ｓｍ－Ｎｄ全岩等时线参考年龄为２０１４±４３Ｍａ。其中变质玄武岩具有扁平的ＲＥＥ模型。这说明在早元古,华夏古陆张裂并发生一次陆壳增生事件。对该区与具有逆掩断层性质的Ｍ１大型韧性剪切带有关的含石榴石变晶糜棱岩给出１５１８±１６Ｍａ和１００１±１４Ｍａ的Ｓｍ－Ｎｄ和Ｒｂ－Ｓｒ石榴石十全岩等时线年龄。前者指示原含石榴石变质岩的变质时代;后者指示的是糜棱岩化时代。它们可能分别与中元古时华夏古陆的再次张裂,及晚元古时龙泉群沉积盆地闭合有关。     

Pb Isotope Compositions of Shibaqinghao Gold Deposit in Central Inner Mongolia, China

There are two types of gold ore in Shibaqinghao gold deposit, a mylonite ore and a quartz - vein ore. Pb isotope compositions for mylonite ore are characterized by lower Pb isotope ratios ranging from 16.63 to 17.45 (206Pb/204Pb), 15.31 to15.48 (207Pb/204pb), 36.52 to 38.85 (208Pb/204Pb). They are scattered very close to a model curve of the mantle evolution. These ratios suggest that gold in the mylonite ore might be derived from the country rocks, which originated directly in the upper mantle. Pb isotope compositions for quartz - vein ore are characterized by higher Pb isotope ratios ranging from 18.23 to 19.74 (206Pb/204Pb), 15.69 to 15.89 (207Pb/204Pb), 38.64 to 40. 13 (208Pb/204Pb). They are scattered very close to a model curve of the upper crustal evolution. These facts indicate that the gold in the quartz - vein ore might be related to some granitic magma generated in the crust.     

初论韧性断裂构造形成时限的研究方法

韧性断裂构造形成时限的研究自提出以来得到了一定程度的发展,目前的研究方法主要有反应速率法、扩散速率法和应变速率法3种。最近的研究表明,对同一韧性剪切带,应变速率法和有限应变测量法所得构造形成时限均以104a为数量级,并且均随着糜棱岩化程度的增加而逐渐减小;不同韧性剪切带的构造形成时限也均以104a为数量级,其差异是由构造动力学条件不同引起的。利用应变速率法所得构造形成时限具有较好的内部一致性,这在一定程度上表明利用应变速率法测定构造形成时限是可行的。在超薄片厚度、不活动组份、糜棱岩化温度和最适用古应力计等的确定上目前仍存在争议。文中还对体积因子和糜棱岩化程度等对求算构造形成时限的影响以及构造形成时限的发展方向进行了深入讨论。构造形成时限研究整体来说仍处于探索阶段,目前只能达到半定量的程度,有待进一步的深入细致的工作,同时也有待于显微构造地质学、构造岩石学等相关学科的进一步发展。     

郯庐断裂南段韧性构造岩天然气突破压力的测算

糜棱岩作为典型韧性构造岩广泛分布于盆地的深部、边部及与之相邻的山链中,其对深源天然气(尤其是无机成因CO₂)的封闭作用尚缺乏研究。本文在扫描电镜观测的基础上,运用气体吸附法和压汞法对郯庐断裂系南段糜棱岩和高级片麻岩的微孔隙结构参数进行了测试。糜棱岩的突破压力多数大于25MPa,其中有40%的样品在50MPa以上,中值半径多数为0.01nm,孔隙集中范围在2.5～16nm,含量10%左右。其微孔隙结构远远优于已知的低、中、高压气藏的实际盖层,表明糜棱岩是天然气的一种优质盖层。     

Propagation of seismic slip from brittle to ductile crust: Evidence from pseudotachylyte of the Woodroffe thrust, central Australia

The Woodroffe thrust, central Australia, is a > 1.5-km-wide mylonitized shear zone marked by large volumes of mm- to cm-scale pseudotachylyte veins. The pseudotachylytes display typical melt-origin features, including rounded and embayed clasts, spherulitic and dentritic microlites, and flow structures within a fine-grained matrix. Three types of pseudotachylyte are identified on the basis of deformation texture, vein morphology, and host-rock lithology: cataclasite-related (C-Pt), mylonite-related (M-Pt), and ultramylonite-related (Um-Pt). The M-Pt and Um-Pt veins intrude into mylonite and ultramylonite and are themselves overprinted by subsequent mylonitization. These pseudotachylytes contain an internal foliation defined by flattened porphyroclasts and layering of the fine-grained vein matrix, and the foliation is generally oriented parallel to foliation in the surrounding mylonite and ultramylonite. These observations constrain the timing and environment of M-Pt and Um-Pt pseudotachylyte formation to a protracted period of deformation and mylonitization within the ductile regime of the crust. The M-Pt and Um-Pt veins, as well as the host mylonite, are overprinted by cataclasis and multiple generations of late-stage C-Pt veins that were generated in the brittle-dominated regime of the upper crust during uplift and exhumation of the shear zone.The coexistence of multiple generations of voluminous C-Pt, M-Pt, and Um-Pt veins indicates that the pseudotachylyte veins represent a large number of large earthquakes and accompanying seismic slip over an extended period of seismicity on the Woodroffe thrust. The timing and distribution of pseudotachylyte indicate that the earthquakes nucleated at the base of the brittle-dominated seismogenic zone and propagated down through the brittle–ductile transition into the ductile-dominated regime of the crust.     

夹皮沟金矿床韧性剪切带控矿作用的研究

夹皮沟金矿区韧性剪切带的空间分布大体上有三组,即NE、NW和SN。而NE向形成早于NW和SN方向。对金矿化具有控制作用,特别是NW向不但发育,且规模大,有利提供矿化空间和储矿构造。对矿化带、金矿床(点)和矿化类型等均起到控制作用。最后提出要高度重视在韧性剪切带和糜棱岩带中找金。     

热水条件下花岗质糜棱岩的摩擦滑动实验研究

为了探讨大陆地壳断层深部的力学性质,我们选择了采自红河断裂带的糜棱岩作为实验样品,进行热水条件下的高温高压摩擦滑动实验.实验在一个以气体为介质的高温高压三轴实验系统中进行.实验条件是：有效正应力为200 MPa;孔隙水压为30 MPa（在400 ℃到600 ℃之间为超临界水条件）;温度为100 ℃到600 ℃;轴向加载的速率范围从0.04 μm/s到0.2 μm/s再到1 μm/s.实验结果表明：（1）当温度小于300 ℃时,糜棱岩的摩擦强度随着温度的上升而增大;当温度大于300 ℃时,糜棱岩的摩擦强度随着温度的上升而减小.这种趋势和以往花岗岩的摩擦滑动数据基本一致;（2）糜棱岩在200 ℃和400 ℃时表现为速度弱化,其余温度下为速度强化;（3）糜棱岩与已有花岗岩的摩擦滑动数据并不完全一致;（4）花岗质糜棱岩速度弱化向速度强化转变的温度在430 ℃附近,以此我们可以推测：在变形机制为摩擦滑动的深部条件下,地震成核的深度范围可以比以往的估计更深.     

古震源实体初步研究

古震源区地震断裂成因的假玄武玻璃显微构造、基质成分及其与区域构造演化关系的研究表明.随地壳抬升和相应的温度降低,在大约10～15km的深度上,长石质岩石先于石英质岩石从韧性转变为脆性性状,是导致韧性剪切带中局部应变不稳定和地震发生的主要原因。对地震断层岩石的多样性和地震成因的二相变形理论模型进行了讨论