The North American Cordilleran Anatectic Belt
The North American Cordilleran Anatectic Belt
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DOI：
10.1016/j.earscirev.2021.103576
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发表时间：
2021-03-03
影响因子：
12.1
通讯作者：
Haxel, Gordon B.
中科院分区：
文献类型：
--
作者：
Chapman, James B.;Runyon, Simone E.;Haxel, Gordon B.
北美科迪勒拉深熔带（CAB）是科迪勒拉山脉内陆一个长约3000千米的区域，包含大量晚白垩世至始新世的侵入岩以及与地壳熔融有关的深熔岩。因此，它在规模和体积上可与包括喜马拉雅淡色花岗岩带在内的主要深熔区域相媲美。CAB岩石主要是过铝质、含白云母的淡色花岗岩，主要由元古宙至太古宙变质沉积岩的深熔作用形成。CAB岩石没有喷出岩等同物，通常以厚板状、岩盖以及岩墙/岩床复合体的形式侵位。CAB的范围、位置和年龄表明，它对于理解北美洲的构造演化至关重要，然而，该带很少被作为一个整体来考虑。本文综述了CAB中与地壳熔融有关的地点，并汇编了地球化学、地质年代学和同位素数据，以评估产生这些岩石的熔融条件和过程。地球化学和部分熔融温度（约675 - 775℃）支持无水白云母脱水熔融和/或缺水熔融是主要的熔融反应，并且通常与水过剩熔融和高温（黑云母到角闪石）脱水熔融不一致。CAB岩石在美国科迪勒拉中部最古老，向北和向南逐渐变年轻。在任何一个地点，部分熔融似乎都是一个漫长的过程（≥1000万年），岩浆再熔融和再活化的证据很常见。关于CAB起源的端元假说包括减压、地壳增厚、流体助熔以及来自地幔的热流增加。CAB的不同部分支持不同的假说，没有一个单一的模型可能能够解释整个深熔事件。无论如何，CAB是科迪勒拉造山系统的一个独特组成部分。
The North American Cordilleran Anatectic Belt (CAB) is a similar to 3,000 km long region in the hinterland of the Cordillera that comprises numerous exposures of Late Cretaceous to Eocene intrusive rocks and anatectic rocks associated with crustal melting. As such, it is comparable in size and volume to major anatectic provinces including the Himalayan leucogranite belt. The CAB rocks are chiefly peraluminous, muscovite-bearing leu-cogranite produced primarily by anatexis of Proterozoic to Archean metasedimentary rocks. The CAB rocks lack extrusive equivalents and were typically emplaced as thick sheets, laccoliths, and dike/sill complexes. The extent, location, and age of the CAB suggests that it is integral to understanding the tectonic evolution of North America, however, the belt is rarely considered as a whole. This paper reviews localities associated with crustal melting in the CAB and compiles geochemical, geochronologic, and isotopic data to evaluate the melt conditions and processes that generated these rocks. The geochemistry and partial melting temperatures (ca. 675-775 degrees C) support water-absent muscovite dehydration melting and/or water-deficient melting as the primary melt re-actions and are generally inconsistent with water-excess melting and high-temperature (biotite to amphibole) dehydration melting. The CAB rocks are oldest in the central U.S. Cordillera and become younger towards both the north and south. At any single location, partial melting appears to have been a protracted process (>= 10 Myr) and evidence for re-melting and remobilization of magmas is common. End-member hypotheses for the origin of the CAB include decompression, crustal thickening, fluid-flux melting, and increased heat flux from the mantle. Different parts of the CAB support different hypotheses and no single model may be able to explain the entirety of the anatectic event. Regardless, the CAB is a distinct component of the Cordilleran orogenic system.