近日，美国加州州立大学Andrea Balbas团队报道了，加利福尼亚边缘地带渐新世和中新世喷灯火山活动及其对板块-边界过渡的影响。相关论文于2024年5月14日发表在《地质学》杂志上。

据研究人员介绍，加利福尼亚边缘地带是北美太平洋转换边缘一个独特的广阔而复杂的地区。渐新世至中新世的构造重组，包括大尺度的伸展和垂直轴的旋转，在南加州近海由汇聚边界向转换边界演化过程中，形成了一个由淹没断层盆地、山脊和岛屿组成的网络。

本文提供了新的⁴⁰Ar/³⁹Ar增量加热年龄测定和加利福尼亚边缘地区火山岩的地球化学分析数据，以及一个协调的区域构造模型。加利福尼亚边缘地带火山岩的成分为钙碱性，主要是二氧化硅过饱和，代表了相对较大程度的软流圈部分熔融，其中包括水合弧前岩石圈成分。对这些记录的时间比对表明，活跃扩张中心从渐新世开始并在中新世再次俯冲，这是对所观察到的ca.31-30Ma和19-13Ma火山活动的关键控制因素。

团队研究人员假设，长时间的海沟—山脊相互作用产生了喷灯效应，导致了广泛的弧前火山活动和地壳弱化，从而促进了在北美-太平洋板块边界其他地方没有出现的边界地区记录的独特变形样式。

附：英文原文

Title: Oligocene and Miocene blowtorch volcanism within the California Borderland and its influence on the plate-boundary transition

Author: Andrea Balbas, Kevin Konrad, Nathan Onderdonk, Paterno R. Castillo, Richard Behl

Issue&Volume: 2024-05-14

Abstract: The California Borderland is a uniquely broad and complex region of the North AmericanPacific transform margin. Oligocene to Miocene structural reorganization, including large-magnitude extension and vertical-axis rotation of crustal blocks, formed a network of submerged fault-bounded basins, ridges, and islands offshore of southern California during its evolution from a convergent to transform boundary. Here, we report new ⁴⁰Ar/³⁹Ar incremental heating age determinations and geochemical analyses of volcanic rocks in the California Borderland, as well as a reconciled regional tectonic model. The California Borderland volcanic rocks are calc-alkaline in composition and mostly silica-oversaturated and represent relatively large-degree partial melts of the asthenosphere that incorporated hydrated forearc lithospheric components. A temporal reconciliation of these records shows that subduction of an active spreading center starting in the Oligocene and again in the Miocene was the critical control on the observed volcanism at ca. 31-30 Ma and 19-13 Ma. We posit that prolonged trench-ridge interaction generated a blowtorch effect, which resulted in widespread forearc volcanism and weakening of the crust to facilitate the unique deformation styles documented in the borderland that did not occur elsewhere along the North AmericanPacific plate boundary.

DOI: 10.1130/G52175.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52175.1/644086/Oligocene-and-Miocene-blowtorch-volcanism-withinredirectedFrom=fulltext