An Investigation of Crustal and Upper Mantle Magmatic Sources in the High Plains Province, New Mexico and Colorado, A Unique View into Late Cenozoic Magmatic...

在新生代，火山活动和伸展构造活动遍及美国西部的广大地区。近年来的研究对美国西部构造活动和岩浆活动之间的关系提供了许多见解，但有关伸展动力的问题仍然没有解决。高平原新生代火山岩为研究这类问题提供了独特的视角。这些火山岩在成分上大致相似，与里约热内卢大裂谷和西南进入亚利桑那州的火山场密切同时代。然而，高平原火山场位于b里约热内卢大裂谷以东100-200公里处，远远超出了地壳伸展的影响。我们的初步研究表明，火山岩组成的时空变化（如同位素变化）要求源区组成和地壳、地幔结构存在显著差异。对该火山场的详细研究将有助于与伸展区域内的火山场进行比较，并为解释岩浆作用与伸展构造作用之间关系的物理模型提供必要的约束条件。

Volcanism and extensional tectonism spread across a broad region of the western U.S. during the Cenozoic. Studies in recent years have provided much insight into the relationship between the tectonism and magmatism in the western U.S., but unsolved questions relating to the driving forces for extension remain. The Cenozoic volcanic rocks of the High Plains provide a unique perspective on such problems. These volcanic rocks are broadly similar in composition and closely contemporaneous with volcanic fields in the Rio Grande Rift and southwestward into Arizona. However, the High Plains volcanic fields lie 100-200 km east of the Rio Grande Rift in an area well beyond the effects of crustal extension. Spatial and temporal variations in composition of volcanic rocks shown from our preliminary study (e.g., isotopic changes) require significant differences in source composition and crust and mantle structure. A detailed study of this volcanic field will enable comparison with fields within the region of extension and provide essential constraints for physical models explaining relationship between magmatism and extensional tectonism.