五台山西部狐狸山含金韧性剪切带的地球化学研究

狐狸山金矿区，在无蚀变作用参与的韧性变形过程中，岩石化学成分发生了明显的变化。但大多数微量元素含量变化不大，稀土元素配分模式基本不变，它们可以反映原岩的特点。蚀变糜棱岩型矿体与围岩相比，稀土配分模式、亲硫元素Ａｕ、Ａｇ、Ｃｕ和两性元素Ａｓ、Ｓｂ含量差别显著，尤其是Ａｕ含量，前者是后者的百倍～几万倍，金的成矿作用主要与韧性变形后期富金流体的蚀变作用关系密切。     

剪切带的流体－岩石相互作用

作为大陆岩石圈中的应变局部化带，剪切带中一般都渗透着大量流体。流体的来源与剪切带所处的构造背景、流变域和水文条件有关，而剪切带中流体的流动则受岩石的渗透率、孔隙度、孔隙性质、流体的扩散和渗透能力、环境的温压条件、应力或载荷的梯度等因素所制约。剪切带中流体的成分、通量及赋存状态或流动方式，直接影响着岩石的流变。由应变局部化及力学失稳所引起的化学不平衡和由流体与岩石的相互作用，使剪切带岩石的矿物成分和化学成分发生调整，其变异程度取决于原岩的性质、剪切的温压条件和流体的成分及通量等。由于流体的渗透流动和流体与岩石的相互作用使剪切带的体积有所变化，体积变化过程是一种自组织行为。较大的体积亏损，意味着剪切带中渗透过大量的流体，这对剪切带的流变行为、化学行为和成矿作用都有深刻的影响。     

Rare earth and other trace element mobility during mylonitization: a comparison of the Brevard and Hope Valley shear zones in the Appalachian Mountains, USA

In progressing from a granitoid mylonite to an ultramylonite in the Brevard shear zone in North Carolina, Ca and LOI (H₂O) increase, Si, Mg, K, Na, Ba, Sr, Ta, Cs and Th decrease, while changes in Al, Ti, Fe, P, Sc, Rb, REE, Hf, Cr and U are relatively small. A volume loss of 44% is calculated for the Brevard ultramylonite relative to an Al–Ti–Fe isocon. The increase in Ca and LOI is related to a large increase in retrograde epidote and muscovite in the ultramylonite, the decreases in K, Na, Si, Ba and Sr reflect the destruction of feldspars, and the decrease in Mg is related to the destruction of biotite during mylonitization. In an amphibolite facies fault zone separating grey and pink granitic gneisses in the Hope Valley shear zone in New England, compositional similarity suggests the ultramylonite is composed chiefly of the pink gneisses. Utilizing an Al–Ti–Fe isocon for the pink gneisses, Sc, Cr, Hf, Ta, U, Th and M-HREE are relatively unchanged, Si, LOI, K, Mg, Rb, Cs and Ba are enriched, and Ca, Na, P, Sr and LREE are lost during deformation. In contrast to the Brevard mylonite, the Hope Valley mylonite appears to have increased in volume by about 70%, chiefly in response to an introduction of quartz. Chondrite-normalized REE patterns of granitoids from both shear zones are LREE-enriched and have prominent negative Eu anomalies. Although REE increase in abundance in the Brevard ultramylonites (reflecting the volume loss), the shape of the REE pattern remains unchanged. In contrast, REE and especially LREE decrease in abundance with increasing deformation of the Hope Valley gneisses. Mass balance calculations indicate that ≥95% of the REE in the Brevard rocks reside in titanite. In contrast, in the Hope Valley rocks only 15–40% of the REE can be accounted for collectively by titanite, apatite and zircon. Possible sites for the remaining REE are allanite, fluorite or grain boundaries. Loss of LREE from the pink gneisses during deformation may have resulted from decreases in allanite and perhaps apatite or by leaching ofy REE from grain boundaries by fluids moving through the shear zone. Among the element ratios most resistant to change during mylonitization in the Brevard shear zone are La/Yb, Eu/Eu*, Sm/Nd, La/Sc, Th/Sc, Th/Yb, Cr/Th, Th/U and Hf/Ta, whereas the most stable ratios in the Hope Valley shear zone are K/Rb, Rb/Cs, Th/U, Eu/Eu*, Th/Sc, Th/Yb, Sm/Nd, Th/Ta, Hf/Ta and Hf/Yb. However, until more trace element data are available from other shear zones, these ratios should not be used alone to identify protoliths of deformed rocks.     

用扭剪试验成果求剪切模量的计算公式

土的剪切模量是土工计算重要参数之一，通常是用弹性模量与们松比间接求得。本文结合扭转翼板仪的工作原理及其边界条件，推出用扭转力矩M和扭转剪切角θ直接求取剪切模量的计算公式。     

湘中雪家坡脆韧性剪切构造岩地球化学特征

在１∶５万黄材幅区调中，对脆韧性剪切构造岩进行的岩石化学、微量元素、稀土元素研究表明，由中细粒含斑二云母二长花岗岩改造为糜棱岩化花岗岩、初糜棱岩、绢云母糜棱岩、硅化糜棱岩、千糜岩、糜棱片岩等，其化学成分发生了不同程度的改变。化学元素的分散、聚集或不变，既受原岩控制（继承性），又受变形强度和流体的成分、性质、活动性等控制（变化性）。     

40Ar/39Ar geochronology and exhumation of mylonitized metamorphic complex in Changle-Nanao ductile shear zone

New⁴⁰Ar/³⁹Ar plateau ages from rocks of Changle-Nanao ductile shear zone are 107.9 Ma(Mus), 108.2 Ma(Bi), 107.1 Ma(Bi), 109.2 Ma(Hb) and 117.9 Ma(Bi) respectively, which are concordant with their isochron ages and record the formation age of the ductile shear zone. The similarity and apparent overlap of the cooling ages with respective closure temperatures of 5 minerals document initial rapid uplift during 107–118 Ma following the collision between the Min-Tai microcontinent and the Min-Zhe Mesozoic volcanic arc. The⁴⁰Ar/³⁹ Ar plateau ages, K-Ar date of K-feldspar and other geochronologic information suggest that the exhumation rate of the ductile shear zone is about 0.18–1.12 mm/a in the range of 107–70 Ma, which is mainly influenced by tectonic extension.     

沉降量约束下的黄骅裂谷形成的地球的动力学模式

在计算覆盖整个黄晔裂谷２００口人工井（包括少部分探井）沉降量的基础上，总结本区二种基本沉降曲线模式。统计出热沉降（Ｓｔ）与初始沉降（Ｓｉ）之比为０．６，依此为约束条件与大陆岩石圈伸展的地球动力学正演模式进行对比，与简单剪切模式预测的热沉降与初始沉降之比值及几何效应更接近。进一步证实黄骅裂谷以简单剪切机制形成的地球动力学模式更合理，这与著名的以纯剪模式形成的北海伸展盆地不同     

造山带岩浆活动与构造运动关系研究综述

熔体及其活动在造山带的演化中发挥了重要作用。熔体活动发迹了地壳应力作用方式而诱发形成剪切带或断层；熔体活动调整块体间的位移而影响造山带的变形；     

Development of joints and shear fractures in the Kuqa depression and its implication to regional stress field switching

The superimposed basin must have undergone the changes of regional stress field. Study on the nature and switch of regional stress field of superimposed basin is very useful to understanding its stress state and tectonic events during its formation and evolution. As sensitive markers of small stress changes, joint and shear fracture, characterized by consistency of orientation over wide area, can be used to reconstruct paleostress state and its evolution. Detailed observations and analysis on the orientations, geometrical patterns, sequences of joints and shear fractures and their chronological relation to faults and folds show that, the NEE-SWW systematic joints and NNW-SSE systematic joints developed in the Mesozoic and Cenozoic strata are much more prominent than NW-SE systematic joints and shear fractures with different orientations. And the NWW-SEE and NW-SE systematic joints formed later than NEE-SWW systematic joints but earlier than shear fractures with different orientations. According to the relationships between joint and shear fractures and stress, the NEE-SWW systematic joints are inferred to result from lateral weak extension caused by the late Cretaceous regional uplift, while the NNW-SSE and NW-SE systematic joints are interpreted as syn-tectonic deformation relating to strong N-S compression in the Neogene. But some conjugate shear fractures occur probably due to sinistral strike-slip faulting in the Kuqa depression. At the beginning of the Neogene, the stress field changed and the maximal principal stress σ1 switched from vertical to horizontal.     

Are open fractures necessarily aligned with maximum horizontal stress?

Fluid flow in fractured rock is an increasingly central issue in recovering water and hydrocarbon supplies and geothermal energy, in predicting flow of pollutants underground, in engineering structures, and in understanding large-scale crustal behaviour. Conventional wisdom assumes that fluids prefer to flow along fractures oriented parallel or nearly parallel to modern-day maximum horizontal compressive stress, or S_Hmax. The reasoning is that these fractures have the lowest normal stresses across them and therefore provide the least resistance to flow. For example, this view governs how geophysicists design and interpret seismic experiments to probe fracture fluid pathways in the deep subsurface. Contrary to these widely held views, here we use core, stress measurement, and fluid flow data to show that S_Hmax does not necessarily coincide with the direction of open natural fractures in the subsurface (>3 km depth). Consequently, in situ stress direction cannot be considered to predict or control the direction of maximum permeability in rock. Where effective stress is compressive and fractures are expected to be closed, chemical alteration dictates location of open conduits, either preserving or destroying fracture flow pathways no matter their orientation.