Origin of palaeofluids in a normal fault setting in the Aegean region
Origin of palaeofluids in a normal fault setting in the Aegean region
复制标题
爱琴海地区正常断层环境中古流体的起源
DOI：
--
复制
发表时间：
2004
期刊：
影响因子：
--
通讯作者：
D. Richards
中科院分区：
文献类型：
--
作者：
G. Verhaert;P. Muchez;M. Sintubin;D. Similox;S. Vandycke;E. Keppens;E. Hodge;D. Richards
布尔杜尔省（土耳其西南部）是地震活跃区。对延伸脉和与断层相关的方解石沉淀物进行了结构、年代学、岩石学、地球化学和流体包裹体研究，以重建爱琴海地区正常断层环境中的古流体流动模式。沉淀物的古应力分析和 U/Th 测年揭示了方解石样品的新构造意义。方解石填充延伸脉的流体包裹体显微测温显示最终熔化温度（Tm 冰）为 0°C。这表明纯净水，很可能来自流星。这些方解石的氧同位素值（-9.8‰至-6.5‰ VPDB）和碳同位素组成（-10.4‰至-2.9‰ VPDB）也显示了导致降水的流体的近地表流星起源。与断层相关的方解石的微观结构特征表明方解石的沉淀与断层活动有关。与断层相关的方解石的最终熔化温度范围在 0 至 -1.9°C 之间。氧同位素值显示在-15.0‰ 和-2.2‰ VPDB 之间的宽范围。其中一些方解石的 δ18O 组成高于或低于该地区陨石方解石的氧同位素组成（即介于 -10‰ 和 -6‰ VPDB 之间）。 δ13C 组成大部分落在宿主石灰岩的范围内，反映了岩石缓冲系统。显微测温和稳定同位素研究表明，这些流体的起源是大气，具有一定程度的水-岩相互作用或与另一种流体的混合。根据显微测温和稳定同位素分析推导出的温度表明降水温度约为 50°C。这些较高的温度和水-岩石相互作用的证据表明，水流路径足够长，足以与母岩石灰岩平衡并提高温度。
对伸展脉和断层相关的方解石沉淀物的综合研究能够确定在正常断层环境中负责沉淀的流体的来源。大气水渗透到石灰岩中至少 1 公里的深度，并发生水-岩相互作用或与残余流体混合。此外，这种流体是在断层活动期间被抽取的。相反，延伸脉体被动地充满了从向下迁移的大气水中沉淀出来的方解石。
The province of Burdur (SW Turkey) is seismically an active region. A structural, geochronological, petrographical, geochemical and fluid inclusion study of extension veins and fault-related calcite precipitates has been undertaken to reconstruct the palaeofluid flow pattern in this normal fault setting in the Aegean region. A palaeostress analysis and U/Th dating of the precipitates reveals the neotectonic significance of the sampled calcites. Fluid inclusion microthermometry of calcites-filling extension veins shows final melting temperatures (Tm ice) of 0°C. This indicates pure water, most likely of meteoric origin. The oxygen isotope values (−9.8‰ to −6.5‰ VPDB) and the carbon isotopic composition (−10.4‰ to −2.9‰ VPDB) of these calcites also show a near-surface meteoric origin of the fluid responsible for precipitation. The microstructural characteristics of fault-related calcites indicate that calcite precipitation was linked with fault activity. Final melting temperature of fault-related calcites ranges between 0 and −1.9°C. The oxygen isotope values show a broad range between −15.0‰ and −2.2‰ VPDB. Several of these calcites have a δ18O composition that is higher or lower than the oxygen isotopic composition of meteoric calcites in the area (i.e. between −10‰ and −6‰ VPDB). The δ13C composition largely falls within the range of the host limestones and reflects a rock-buffered system. Microthermometry and stable isotopic study indicate a meteoric origin of the fluids with some degree of water–rock interaction or mixing with another fluid. Temperatures deduced from microthermometry and stable isotope analyses indicate precipitation temperatures around 50°C. These higher temperatures and the evidence for water–rock interaction indicate a flow path long enough to equilibrate with the host–rock limestone and to increase the temperature.
The combined study of extension vein- and fault-related calcite precipitates enables determining the origin of the fluids responsible for precipitation in a normal fault setting. Meteoric water infiltrated in the limestones to a depth of at least 1 km and underwent water–rock interaction or mixing with a residual fluid. This fluid was, moreover, tapped during fault activity. The extension veins, on the contrary, were passively filled with calcites precipitating from the downwards-migrating meteoric water.