近日，美国北伊利诺伊大学Suzanne Autrey-Mulligan最新的研究对美国大峡谷前寒武纪基底内的压力差进行了分解，研究结果阐明了其对元古代构造的影响。这一研究成果发表在2024年1月25日出版的国际学术期刊《地质学》上。

研究人员报道了来自大峡谷ca.1.7 Ga的上花岗岩峡谷(UGG)岩石的精确的变质压力，并首次分解了中地壳岩石持续暴露的压力变化。研究人员应用石榴子石中的石英(QuiG)进行气压测定法和伪断面建模，以确定具有更高和更低峰值变质等级证据的区域(“地块”)中的压力。

研究使用的这种综合方法构建的新压力—温度(P-T)路径显示，热地块样品达到7kbar，冷地块样品从未超过5kbar，结果揭示了热地块和冷地块之间存在约2kbar的压力差异，并描绘了UGG中这些域的不同的P-T路径。

研究发现，热地块和冷地块可能在前Yavapai、古元古代造山带的不同地壳水平上变质，随后在Yavapai造山运动期间和/或之后再中地壳层面并置。产生地壳块体差异垂直位移的变形，发生在晚期峰变质作用之后，可能反映了古元古代Laurentian板块边缘大型造山带的伸展崩塌和/或重新褶皱和逆冲作用。

据介绍，山脉带内的埋藏压力(深度)对大陆地壳的生长和稳定构成了根本性的限制。

附：英文原文

Title: Resolving pressure differences within the Grand Canyon Precambrian basement: Implications for Proterozoic tectonics

Author: Suzanne Autrey-Mulligan, Chloe Bonamici, Michael L. Williams, Karl Karlstrom, Cailey B. Condit

Issue&Volume: 2024-01-25

Abstract: Burial pressures (depths) within mountain belts place fundamental constraints on the growth and stabilization of continental crust. We report precise metamorphic pressures for ca. 1.7 Ga rocks from the Upper Granite Gorge (UGG) of the Grand Canyon (southwestern United States) and, for the first time, resolve pressure variations across this continuous exposure of mid-crustal rocks. We applied quartz-in-garnet (QuiG) barometry and pseudosection modeling to determine pressures in domains (“blocks”) with evidence of higher and lower peak metamorphic grades. New pressure-temperature (P-T) paths constructed using this integrated approach show that a hot block sample reached 7 kbar and a cold block sample never surpassed 5 kbar, revealing an ～2 kbar P difference between hot and cold blocks and delineating distinct P-T paths for these domains in the UGG. Our findings suggest that hot and cold blocks were likely metamorphosed at different crustal levels within a pre-Yavapai, Paleoproterozoic orogen and were subsequently juxtaposed during and/or after the Yavapai Orogeny at mid-crustal levels. The deformation that produced differential vertical displacement of crustal blocks post-dated peak metamorphism and could reflect extensional collapse of a large orogen and/or renewed folding and thrusting at the Paleoproterozoic Laurentian plate margin.

DOI: 10.1130/G51706.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51706.1/633577/Resolving-pressure-differences-within-the-GrandredirectedFrom=fulltext