Thermal evolution of the Sierra Nevada: Tectonic implications of new heat flow data
Thermal evolution of the Sierra Nevada: Tectonic implications of new heat flow data
复制标题
内华达山脉的热演化：新热流数据的构造意义
DOI：
10.1029/90tc02681
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发表时间：
1991
期刊：
影响因子：
4.2
通讯作者：
A. Lachenbruch
中科院分区：
文献类型：
--
作者：
R. Saltus;A. Lachenbruch
内华达山脉南部的8个新的热流测量限制了热演化和岩石圈结构的模型。内华达山脉西南部的低减少热流（18 - 21 mW/m²）与之前内华达山脉西北部和中部的结果一致，并将已知的线性热流-产热相关区域向南扩展了150公里。在内华达山脉中部，均衡剩余重力和测量岩石密度也呈线性相关，这表明上地壳密度分布与产热之间存在普遍联系。剩余重力-密度线性关系表明均衡剩余重力异常有上地壳来源，因此是反对新生代内华达山脉隆起弯曲模型的证据。在内华达山脉东南部测量到的新减少的热流相对较高（32至57 mW/m²），并且在空间上与包括伸展地震群的高地震活动性区域相关；这种对比支持了盆地和山脉伸展构造以及相关岩浆作用正在侵入内华达山脉东部的观点。在稳定的内华达山脉西南部，与内华达山脉中部和西北部一样，地表持续的低减少热流与内华达山脉新生代隆起的热源一致，前提是导电岩石圈至少有60至90公里厚。简单的数量级计算表明，结合地幔岩石圈平流增温减薄、玄武岩岩浆和热量向地壳平流、简单热膨胀和榴辉岩-玄武岩相转换等机制的热隆升模型可以解释新生代内华达山脉隆升的时间和数量。热模型不需要力学模型对中生代地壳根驱动的新生代隆升所要求的异常岩石圈强度和地壳浮力的假设。
Eight new heat flow measurements in the southern Sierra Nevada constrain models of thermal evolution and lithospheric structure. Low reduced heat flows (18 to 21 mW/m²) in the southwest Sierra Nevada are consistent with previous results from the northwestern and central Sierra Nevada and extend the known region of linear heat flow-heat production correlation an additional 150 km to the south. Isostatic residual gravity and measured rock densities are also linearly correlated in the central Sierra Nevada, suggesting a general association between the upper crustal distribution of density and heat production. The linear residual gravity-density relation implies that isostatic residual gravity anomalies have upper crustal sources and therefore is evidence against a flexural model of Cenozoic Sierra Nevada uplift. New reduced heat flows measured in the southeast Sierra Nevada are relatively high (32 to 57 mW/m²) and correlate spatially with a region of high seismicity that includes extensional earthquake swarms; this correlation supports the view that Basin and Range extensional tectonics and associated magmatic processes are encroaching on the eastern Sierra Nevada. In the stable southwest Sierra Nevada, as in the central and northwestern Sierra Nevada, the persistence of low reduced heat flow at the surface is consistent with a thermal origin for the Cenozoic uplift of the Sierra Nevada, provided the conductive lithosphere is at least 60 to 90 km thick. Simple order-of-magnitude calculations show that thermal uplift models combining mechanisms such as advective warming and thinning of the mantle lithosphere, advection of basaltic magma and heat into the crust, simple thermal expansion, and eclogite-to-basalt phase conversion can account for the timing and amount of Cenozoic Sierra Nevada uplift. Thermal models do not need the assumptions of unusual lithospheric strength and crustal buoyancy required by mechanical models for Cenozoic uplift driven by a Mesozoic crustal root.