Thermal and kinematic model of the southern Rio Grande rift: inferences from crustal and mantle xenoliths from Kilbourne Hole, New Mexico
Thermal and kinematic model of the southern Rio Grande rift: inferences from crustal and mantle xenoliths from Kilbourne Hole, New Mexico
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DOI：
10.1016/0040-1951(91)90051-s
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发表时间：
1991-10
期刊：
影响因子：
2.9
通讯作者：
G. Bussod;D. Williams
中科院分区：
文献类型：
--
作者：
G. Bussod;D. Williams
一个简单的热传导模型，受来自 Kilbourne Hole maar 地壳和地幔捕虏体中共存矿物的测压数据的约束。新墨西哥州，用于了解格兰德河裂谷南部裂谷的发展和岩石圈的热演化。一维有限差分代码通过岩浆注入下地壳和最上地幔来模拟地壳减薄和底侵。该模型与地壳和地幔测温阵列非常一致，假设瞬态裂谷前梯度叠加在稳定的地温上，并在 3000 万年前在 40 公里厚的地壳中产生 20°C km−1 的净梯度，在上地幔中产生 3°C km−1 的净梯度。这与该地区裂谷前的火山活动一致，可能与拉拉米德造山事件有关。在最上地幔和地壳底部大量注入玄武岩岩脉和基岩（约 70 vol.%）可能发生在格兰德河裂谷南部的早期发展过程中，即 20 到 30 Ma 之间。岩浆注入产生的热量被视为与温度相关的热源，均匀分布在从 25 公里深度延伸到 45 公里深度的整个侵入区域。地幔和地壳捕虏体的结构观察以及主量和微量元素组成表明，交代作用和重结晶可能发生在20至30 Ma的液体渗透和部分熔融过程中。这与与地壳污染相关的早期裂谷双峰式火山活动一致，并与约 25% 的总 NE-SW 延伸有关。随着中新世中期火山活动的平息，岩脉注入和地壳变薄停止了 20 Ma。每百万年每公里裂谷长度注入 100 立方公里的物质总量，大约比典型的洋中脊少一个数量级。根据在里奥格兰德裂谷南部观测到的当前值，最上地幔（40-45公里深度）从超过1200°C（22 Ma）的温度进行传导冷却，导致麻粒岩变质地壳复合体的形成，并产生82 mW m−2的表面热流。总体而言，岩脉注入模型的结果与地壳和地幔测温阵列以及来自格兰德河裂谷南部的当前地球化学和地球物理数据一致。
A simple thermal conduction model constrained by piezothermometric data obtained from coexisting minerals in both crustal and mantle xenoliths from Kilbourne Hole maar. New Mexico, is used to understand the development of rifting and the thermal evolution of the lithosphere in the southern Rio Grande rift. The one-dimensional finite difference code models crustal thinning and underplating by magmatic injection into the lower crust and uppermost mantle. The model is in good agreement with crustal and mantle thermometric arrays assuming a transient, pre-rift gradient superimposed on a stable geotherm and yielding a net gradient of 20°C km−1in the 40-km-thick crust and 3°C km−1in the upper mantle 30 million years ago. This is consistent with pre-rift volcanic activity in the area possibly related to Laramide orogenic events. A massive injection of basaltic dikes and sills ( ≈ 70 vol.%) in the uppermost mantle and at the base of the crust probably occurred in the early development of the southern Rio Grande rift, between 20 and 30 Ma. The heat contribution due to the injection of magma is treated as a temperature-dependent heat source distributed uniformly throughout the intruded region which extends from 25 to 45 km depth. Textural observations along with major and trace element compositions of the mantle and crustal xenoliths indicate that metasomatism and recrystallization may have occurred during liquid infiltration and partial melting 20 to 30 Ma. This is consistent with early rift bimodal volcanism associated with crustal contamination and linked to approximately 25% total NE-SW extension. Dike injection and crustal thinning ceased 20 Ma associated with the mid-Miocene lull in volcanic activity. The total volume of material injected, 100 km3per km length of rift per million years, is approximately an order of magnitude less than for a typical mid-ocean ridge. Conductive cooling of an uppermost mantle (40–45 km depth) from temperatures of over 1200°C (22 Ma) leads to the formation of a granulite metamorphic crustal complex and generation of a surface heat flow of 82 mW m−2, in accordance with observed present-day values in the southern Rio Grande rift. Overall, the results from the dike injection model are consistent with both the crustal and mantle piezothermometric arrays and present-day geochemical and geophysical data from the southern Rio Grande rift.