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首页> 外文期刊>Geodinamica Acta >Quartz and calcite microfabric transitions in a pressure and temperature gradient, Sivrihisar, Turkey
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Quartz and calcite microfabric transitions in a pressure and temperature gradient, Sivrihisar, Turkey

机译：压力和温度梯度下的石英和方解石微纤维转变，土耳其Sivrihisar

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摘要

Interlayered quartzite and marble in the southern Sivrihisar Massif, Turkey, record metamorphic conditions ranging from high-pressure/low-temperature through a Barrovian overprint from chlorite- to sillimanite-zone conditions. This sequence was exhumed under transtension, producing macroscopic constrictional fabrics (L-tectonites) during crustal thinning. Quartz microstructures consist of dynamically recrystallized aggregates in the dislocation creep regime dominated by grain boundary migration. Quartz microstructures are relatively constant across the high metamorphic gradient, and crystallographic fabric patterns transition from plane strain to constriction strain. Calcite fabrics are characterized by progressive overprinting of a columnar texture inherited from the high-pressure polymorph aragonite. In the low-temperature Barrovian domain (<400 ℃), shearing of calcite rods produced a very strong c-axis point maximum. At moderate temperature, calcite rods were partially to totally recrystallized and the strong preferred orientation maintained. At temperature >500 ℃ and high constriction strain, marble has no crystallographic fabric, likely reflecting a transition from dislocation creep to diffusion creep. Phengite in high-pressure/low-temperature marble and quartzite yields relatively simple age spectra with Late Cretaceous (88-82 Ma) ~(40)Ar/~(39)Ar ages. Barrovian muscovite records significantly younger ages (63-55 Ma). The transtension system and associated metamorphism may have occurred above a subduction zone in Paleocene-Eocene time as a precursor to intrusion of Eocene (~53 Ma) arc plutons.
机译：土耳其Sivrihisar地块南部的夹层石英岩和大理石记录了变质条件，从高压/低温到从绿泥石区到硅线石区的Barrovian叠印。该序列在变伸作用下被挖掘出，在地壳变薄过程中产生了宏观的收缩织物（L-构造体）。石英微结构由位错蠕变状态下以晶界迁移为主的动态重结晶聚集体组成。石英的微观结构在较高的变质梯度范围内相对恒定，并且结晶织物的图案从平面应变过渡到压缩应变。方解石织物的特征是，从高压多晶型文石继承的圆柱状纹理逐渐叠印。在低温Barrovian域（<400℃），方解石棒的剪切产生非常强的c轴点最大值。在中等温度下，方解石棒部分重结晶至完全重结晶，并保持了强烈的首选取向。在> 500℃的温度和高压缩应变下，大理石没有晶体结构，可能反映了从位错蠕变到扩散蠕变的过渡。高压/低温大理石和石英岩中的亚硫酸盐产生相对简单的年龄谱，晚白垩世（88-82 Ma）〜（40）Ar /〜（39）Ar年龄。巴罗夫白云母记录的年龄明显较小（63-55 Ma）。在新世-始新世的俯冲带上方可能已经发生了超高压系统和相关的变质作用，这是始新世（〜53 Ma）弧形云母侵入的先兆。

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