Microtectonics and 39Ar−40Ar dating of high pressure metamorphic rocks of the south Ryukyu Arc and their bearings on the pre-Eocene geodynamic evolution of Eastern Asia
Microtectonics and 39Ar−40Ar dating of high pressure metamorphic rocks of the south Ryukyu Arc and their bearings on the pre-Eocene geodynamic evolution of Eastern Asia
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南琉球岛弧高压变质岩的微构造和39Ar−40Ar测年及其对东亚前始新世地球动力学演化的影响
DOI：
10.1016/0040-1951(88)90287-9
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发表时间：
1988
期刊：
影响因子：
2.9
通讯作者：
O. Fabbri
中科院分区：
文献类型：
--
作者：
M. Faure;P. Monié;O. Fabbri
在八重山群岛（琉球岛弧南部）发现的始新世前变质岩与日本和台湾的变质岩的关系存在争议。分为Tomuru组和Fusaki组。1.(1)Tomuru组由来自海洋沉积物和最上层洋壳的高压(HP)变质岩组成。第一变形阶段的特征是同变质的西北-东南走向的拉伸线状（L1）。运动学分析表明，该变形对应于沿L1从西北向东南方向的近水平韧性剪切。2.(2)Fusaki组或混沌地层是三叠系或下侏罗统放射虫橄榄岩的橄榄石。假设基质的年龄为侏罗纪晚期。它呈轻微片状，仅观察到 S-vergent 变形相。推测高压片岩逆冲中生代长片岩。对Tomuru组多硅白硅灰岩和Na角闪石进行了39Ar-40Ar逐步加热实验。白硅白云母和分区的菱锰矿-斜方矿分别在 225 ± 4.8 Ma 和 237 ± 6.3 Ma 处给出了明确的平台。它们被解释为延性变形的年龄。 Crossite 产生的综合数据为 104.8 ± 8.3 Ma，解释为高压片岩冲顶到混沌地层之上的年龄。高压片岩和混沌地层的岩石地层学、岩石学、微构造和39Ar-40Ar年龄分别与日本西南部内带二叠系三群高压片岩和侏罗系丹波长片岩相似。在那里，中生代造山运动期间，三群片岩也推覆了丹波长片岩。在台湾也发现了类似丹波的中生代扁线虫，但在中新世时期发生了剧烈的变形和变态。为解释日本西南部晚二叠世至早三叠世造山带而提出的地球动力学碰撞模型已扩展到南琉球和台湾。相反，日本西南部的中生代三波川高压片岩和上侏罗统至下中新统浊积岩和橄榄石（三房山-四万十带）既不出露于南琉球岛弧，也不出露于台湾。讨论了一些假设，要求构造侵蚀或非沉积来解释这种缺失。
The pre-Eocene metamorphic rocks found in the Yaeyama Islands (the southern part of the Ryukyu Arc) have disputed relationships with the metamorphic formations of Japan and Taiwan. They are divided into the Tomuru and Fusaki formations.1.(1) The Tomuru Formation is composed of high pressure (HP) metamorphic rocks derived from oceanic sediments and the uppermost oceanic crust. The first deformation phase is characterized by a synmetamorphic NW-SE trending stretching lineation (L1). Kinematic analysis shows that the deformation corresponds to a subhorizontal ductile shear directed alongL1from the northwest to the southeast.2.(2) The Fusaki Formation or chaotic formation is an olistostrome of Triassic or Lower Jurassic radiolarite olistoliths. The age of the matrix is assumed to be late Jurassic. It is slightly schistose and only a S-vergent deformation phase is observed. It is assumed that theHPschists overthrust the Mesozoic olistostrome.39Ar-40Ar step-heating experiments have been carried out on phengite and Na amphibole from the Tomuru Formation. Phengite and zoned barroisite-crossite give well defined plateaus at 225 ± 4.8 Ma and 237 ± 6.3 Ma respectively. They are interpreted as the age of the ductile deformation. Crossite yields an integrated data of 104.8 ± 8.3 Ma, interpreted as the age of the thrusting of the HP schists above the chaotic formation. The lithostratigraphy, petrology, microtectonics and39Ar-40Ar ages of the HP schists and the chaotic formation are similar to the Permian Sangun HP schists and the Jurassic Tanba olistostrome of the Inner Belt of southwestern Japan respectively. There, the Sangun schists also overthrust the Tanba olistostrome during the Mesozoic orogeny. The same Tanba-like Mesozoic olistostrome is also found in Taiwan, but was intensely deformed and metamorphosed in Miocene times. The geodynamic collision model proposed to account for the late Permian to early Triassic orogen of southwestern Japan is extended to the South Ryukyu and Taiwan. Conversely, the Mesozoic Sanbagawa HP schists and the upper Jurassic to lower Miocene turbidites and olistostrome (Sanbosan-Shimanto zones) of southwestern Japan are neither exposed in the south Ryukyu Arc, nor in Taiwan. Hypotheses are discussed that call upon tectonic erosion or non-deposition to account for this absence.
琉球群岛（西南诸岛）
DOI：
--
发表时间：
2005
期刊：
全国シンポジウム『中世窯業の諸相』資料集
影响因子：
--
作者：
山口 敏;石田 肇;池田榮史
通讯作者：
池田榮史