Metamorphic and Thermal History of a Fore- Arc Basin: the Fossil Bluff Group, Alexander Island, Antarctica
Metamorphic and Thermal History of a Fore- Arc Basin: the Fossil Bluff Group, Alexander Island, Antarctica
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DOI：
10.1093/petrology/egh025
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发表时间：
2004-07
影响因子：
3.9
通讯作者：
S. Miller;D. Macdonald
中科院分区：
文献类型：
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作者：
S. Miller;D. Macdonald
亚历山大岛喜马利亚山脊组（化石崖群）是由上侏罗统-下白垩统砾岩、砂岩和泥岩组成的 2.2 公里厚序列，源自安山岩火山弧并沉积在弧前盆地中。地层的变质和热历史已通过自生矿物组合和镜质体反射率测量确定。变质作用包括压实、孔隙空间减少、胶结和溶解，以及碎屑颗粒被粘土矿物（蒙脱石、伊利石/蒙脱石、红柱石和高岭石）、方解石、绿泥石、浊沸石、葡萄石、泵贝利石、钠长石和云母取代，以及较少见的石英、赤铁矿、黄铁矿和绿帘石。自生矿物组合表现出深度依赖性，而浊沸石和方解石表现出强烈的反感关系。泥质层中碎屑有机质的镜质体反射率（R-o）范围为2.3%~3.7%。这表明热成熟程度相当大，反射率随着深度的增加而系统性增加。变质矿物组合与绿泥石结晶度和镜质体反射率值具有良好的相关性，所有指示温度范围为序列顶部的 140 +/- 20 摄氏度到序列底部的 250 +/- 10 摄氏度。温度表明地温梯度为 36-64 摄氏度/公里，最可能的梯度为 50 摄氏度/公里。有人认为，弧前盆地这种高于平均水平的梯度要么是盆地形成期间的裂谷造成的，要么是晚期弧迁移事件造成的。
The Himalia Ridge Formation (Fossil Bluff Group), Alexander Island is a 2.2-km-thick sequence of Upper Jurassic-Lower Cretaceous conglomerates, sandstones and mudstones, derived from an andesitic volcanic arc and deposited in a fore-arc basin. The metamorphic and thermal history of the formation has been determined using authigenic mineral assemblages and vitrinite reflectance measurements. Metamorphic effects include compaction, pore-space reduction, cementation and dissolution and replacement of detrital grains by clay minerals (smectite, illite/smectite, corrensite and kaolinite), calcite, chlorite, laumontite, prehnite, pumpellyite, albite and mica, with less common quartz, haematite, pyrite and epidote. The authigenic mineral assemblages exhibit a depth-dependence, and laumontite and calcite exhibit a strong antipathetic relationship. Detrital organic matter in the argillaceous layers has vitrinite reflectance values (R-o) ranging from 2.3 to 3.7%. This indicates considerable thermal maturation, with a systematic increase in reflectivity with increasing depth. There is good correlation of metamorphic mineral assemblages with chlorite crystallinity and vitrinite reflectance values-all indicating temperatures in the range of 140 +/- 20degreesC at the top of the sequence to 250 +/- 10degreesC at the base of the sequence. The temperatures suggest a geothermal gradient of 36-64degreesC/km and a most likely gradient of 50degreesC/km. It is suggested that this higher-than-average gradient for a fore-arc basin resulted either from rifting during basin formation or from a late-stage arc migration event.