Early to Mid‐Tertiary inverted metamorphic gradient under the Colorado Plateau: Evidence from eclogite xenoliths in ultramafic microbreccias, Navajo Volcanic Field
Early to Mid‐Tertiary inverted metamorphic gradient under the Colorado Plateau: Evidence from eclogite xenoliths in ultramafic microbreccias, Navajo Volcanic Field
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科罗拉多高原下早第三纪倒转变质梯度：纳瓦霍火山田超镁铁质微角砾岩中榴辉岩捕虏体的证据
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
D. Schulze
中科院分区：
文献类型：
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作者：
H. Helmstaedt;D. Schulze
科罗拉多高原四角地区纳瓦霍火山田中第三系超镁铁质微角砾岩中含有超镁铁质包体，其中低温递进变质榴辉岩与高温石榴石单斜辉石伴生，石榴石单斜辉石岩退化水化为绿泥石榴辉岩。变质反应的组合和方向与拉拉米德年龄反转变质梯度的模型一致，该模型建立在脱水的洋板中的进行性反应导致上覆的次大陆上地幔楔体的水化和冷却。与代表亚利桑那州西南部和加利福尼亚州南部同一俯冲系统裸露部分的佩洛纳片岩中的逆变质梯度进行比较，证实了与俯冲相关的火山岩的区域分布所预测的拉拉米德俯冲带的浅倾角。
Mid-Tertiary ultramafic microbreccia diatremes from the Navajo volcanic field in the Four Corners area of the Colorado Plateau contain an ultramafic xenoliths suite in which lower-temperature, prograde-metamorphic eclogites are associated with higher-temperature garnet clinopyroxenites that were retrograded and hydrated to chlorite eclogite. Assemblages and directions of metamorphic reactions are consistent with the model of a Laramide age inverted metamorphic gradient established as prograde reactions in a dehydrating oceanic slab caused hydration and cooling in the overlying, subcontinental upper mantle wedge. Comparison with an inverse metamorphic gradient in the Pelona schists, inferred to represent an exposed part of the same subduction system in southwestern Arizona and southern California, confirms the shallow dip of the Laramide subduction zone predicted by the regional distribution of subduction-related volcanic rocks.