3-D geometry of the Moine thrust and its implications for 3-D strain distribution and thrust sheet kinematics

Moine 推力的 3-D 几何结构及其对 3-D 应变分布和推力片运动学的影响

• 批准号: 0208001
• 负责人: Gautam Mitra
• 金额: $ 16万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-15 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0208001&HistoricalAwards=false
• 关键词: geometry; Moine; thrust; its; implications

Most thrust fault traces are arcuate in nature and are comprised of a series ofsalients and recesses suggesting that thrust faults are, in general, non-planar. Such three-dimensional complexities in the thrust surface geometry may be an important factorcontrolling the thrust fault kinematics. Consider the analogy of glacial ice flowing overan irregular substrate. The major resistance to movement is not due to the frictionbetween the two materials (which is greatly reduced by pressure-melt water that coats thesurface) but due to the distortion of the ice as it flows past surface irregularities. Thrustsheets may behave in a similar manner. Fault rocks are considerably weaker than thehost rock and, therefore, the continued deformation of such rocks may not be the factor inlarge-scale thrust sheet emplacement. The PI suggests that three-dimension irregularities inthrust surface geometry play a major role in thrust sheet kinematics. If this is the case,one should expect that the strain patterns observed along strike of a given thrust fault willreflect the thrust fault geometry. Preliminary studies have shown that both c-axespatterns and relict grain shapes vary along the strike of the fault most likely due to thefault geometry effects. Initial data suggest that deformation is nearly plane strainwithin a prominent salient; but along the margins of the salient there is a strongercomponent of flattening strains. However, further examination of the strains in thisregion are needed to truly resolve this pattern. Three-dimensional finite strain geometrieshave been determined in this region by measuring relict quartz grain shapes andexamining quartz c-axes fabrics. Moreover, it may also be useful to measure final stageincremental strains by determining three-dimensional recrystallized quartz grain shapesand three-dimensional quartz overgrowth geometries. It is only through examiningincremental strain histories that the PI can fully understand the kinematics of thrust faults.Nevertheless, current mechanical models do not take into account the existence ofnon-plane strains and therefore only predict realistic fold-thrust belt behavior to a first-order. In order to make more realistic models for the evolution of fold-and-thrust beltswe must start to incorporate the non-plane strain elements of geometrically complexthrust faults.

大多数逆冲断层的痕迹是弧形的性质，是由一系列的凸起和凹陷，这表明逆冲断层，在一般情况下，非平面。 逆冲断层的三维复杂几何结构可能是控制逆冲断层运动学的一个重要因素。考虑一下冰川在不规则基底上流动的类比。 主要的运动阻力不是由于两种材料之间的摩擦（这是大大减少了压力融化水，覆盖表面），但由于冰的扭曲，因为它流过表面的不规则性。推力板可能会以类似的方式表现。 断层岩比寄主岩弱得多，因此，此类岩石的持续变形可能不是大规模逆冲岩席就位的因素。 PI表明，三维不规则性在逆冲断层面几何形状中起着主要作用。 如果是这样的话，人们应该期望沿着给定逆冲断层的沿着走向观察到的应变模式将反映逆冲断层的几何形状。 初步研究表明，c轴模式和残余颗粒形状沿断层走向沿着变化，很可能是由于断层几何形状的影响。最初的数据表明，变形是近平面应变在一个突出的凸起，但沿着边缘的凸起有一个较强的组件扁平应变。然而，需要对该地区的菌株进行进一步检查，以真正解决这一模式。 通过对残余石英颗粒形状的测量和石英c轴组构的研究，确定了该区的三维有限应变几何。 此外，它也可能是有用的，以测量最终stagegremental应变，通过确定三维再结晶石英晶粒形状和三维石英过度生长的几何形状。 只有通过检查增量应变历史，PI才能完全理解逆冲断层的运动学。然而，目前的力学模型没有考虑非平面应变的存在，因此只能预测现实的褶皱-逆冲带行为的一阶。 为了使褶皱-冲断带的演化模型更加真实，我们必须开始考虑几何形状复杂的逆冲断层的非平面应变单元。