IMPACT OF PHYLLOSILICATE DISTRIBUTION, SPATIAL ARRANGEMENT AND INTERCONNECTIVITY ON QUARTZ RECRYSTALLIZATION, RAFT RIVER MOUNTAINS DETACHMENT SHEAR ZONE, UTAH
IMPACT OF PHYLLOSILICATE DISTRIBUTION, SPATIAL ARRANGEMENT AND INTERCONNECTIVITY ON QUARTZ RECRYSTALLIZATION, RAFT RIVER MOUNTAINS DETACHMENT SHEAR ZONE, UTAH
复制标题
犹他州拉夫河山脉脱离剪切带页硅酸盐分布、空间排列和连通性对石英重结晶的影响
DOI：
10.1130/abs/2021am-366919
复制
发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Casale, Gabriele
中科院分区：
文献类型：
--
作者：
Gottardi, Raphaël;Economou, John;Casale, Gabriele
次生矿物的存在强烈影响粘性变形。例如，石英岩中白云母的存在已被证明会改变石英位错蠕变、重结晶和骨料整体强度的相对速率。白云母倾向于在SC织物的发展过程中形成相互连接的颗粒网络。白云母的这种相互连接标志着流变特性的变化，其中弱相白云母适应应力和应变，导致较弱的聚集体。白云母还抑制动态重结晶的过程中，晶界迁移，防止石英晶粒生长，并鼓励其他机制，如云母中的位错滑移，晶界滑动quartity.To了解白云母如何影响石英变形processes，我们专注于中新世剥离剪切带与筏河变质核杂岩（西北犹他州）。Raft River拆离剪切带位于元古代厄尔巴石英岩中，该石英岩由约90%的石英和5 - 10%的白云母组成。通过X射线计算机断层扫描对白云母分布的成像显示了不同的颗粒形状和空间分布模式：1）短而薄的菱形孤立颗粒，2）大的扁圆盘状颗粒，3）长的棒状互连颗粒。初步岩相学和电子背散射衍射观察表明，白云母分布的风格（棒或盘，连接与孤立的晶粒）与石英晶粒显微结构，晶粒尺寸和晶粒形状的变化相关。石英显微结构与孤立的菱形白云母颗粒表现出残余和再结晶颗粒的分布。残留颗粒通常表现出强烈的波状消光，并经常表现出变形纹层。小的菱形白云母颗粒通常钉扎石英晶界。石英显微结构与棒状互连的白云母颗粒表现出高的纵横比残余颗粒钉扎对白云母，和更大量的重结晶晶粒。重结晶颗粒形成层或带，与糜棱岩面理平行，通常上下被白云母片覆盖。这些结果对石英岩糜棱岩中的流动规律的应用和中地壳剪切带的应变局部化机制具有重要意义。
The presence of secondary minerals strongly affects viscous deformation. For example, the presence of muscovite in a quartzite has been shown to alter the relative rates of quartz dislocation creep, recrystallization, and overall strength of the aggregate. Muscovite tends to form an interconnected network of grains during the development of SC fabrics. This interconnection of muscovite marks a change in rheological properties, in which the weak phase, muscovite, accommodates stress and strain, resulting in a weaker aggregate. Muscovite also inhibits the process of dynamic recrystallization by grain boundary migration, preventing quartz grain growth, and encouraging other mechanisms such as dislocation glide in micas, and grain boundary sliding in quartz.To understand how muscovite affects quartz deformation processes, we focus on the Miocene detachment shear zone associated with the Raft River metamorphic core complex (NW Utah). The Raft River detachment shear zone is localized within the Proterozoic Elba quartzite, which is composed of~ 90% quartz and 5 to 10% muscovite. Imaging of muscovite distribution by X-Ray computed tomography shows different grain shapes and spatial distribution patterns: 1) short and thin, rhomb-shaped, isolated grains, 2) large oblate disc-shaped grains, and 3) long, rod-shaped interconnected grains. Preliminary petrographic and electron backscattered diffraction observations, show that the style of muscovite distribution (rod or disc, connected vs. isolated grains) correlates with a change in quartz grain microstructures, grain size, and grain shape. Quartz microstructures associated with isolated rhombshaped muscovite grains exhibit distribution of relict and recrystallized grains. The relict grains typically display a strong undulose extinction and often exhibit deformation lamellae. The small rhomb-shaped muscovite grains typically pin quartz grain boundaries. Quartz microstructures associated with the rodshaped interconnected muscovite grains exhibit high aspect ratio relict grains pinned against muscovite, and greater amount of recrystallized grains. Recrystallized grains form layers or bands subparallel to the mylonitic foliation, that are typically capped above and below by sheets of muscovite. These results have important implication on the application of flow laws in quartzite mylonites, and strain localization mechanisms in mid-crustal shear zones.