加利福尼亚边界地带的渐新世和中新世喷火火山活动及其对板块边界过渡的影响

Geology Pub Date : 2024-05-14 DOI:10.1130/g52175.1
Andrea Marie Balbas, Kevin Konrad, Nathan W. Onderdonk, P. Castillo, Richard Behl
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摘要

加利福尼亚边陲是北美-太平洋转换边缘的一个独特而宽广的复杂区域。从渐新世到中新世的结构重组,包括地壳块体的大尺度延伸和垂直轴旋转,在其从汇聚边界到转换边界的演化过程中,形成了一个由水下断层环绕的盆地、海脊和南加州近海岛屿组成的网络。在此,我们报告了新的 40Ar/39Ar 增量加热年龄测定结果和加利福尼亚边界地区火山岩的地球化学分析,以及一个协调的区域构造模型。加利福尼亚边界地区的火山岩成分为钙碱性,大部分为二氧化硅过饱和,代表了包含水合前弧岩石圈成分的相对大度部分熔融的星体层。对这些记录的时间调和表明,从渐新世开始的活跃扩张中心的俯冲以及中新世的俯冲,是在约 31-30 Ma 和 19-13 Ma 出现的火山活动的关键控制因素。31-30 Ma 和 19-13 Ma。我们认为,长期的海沟-海脊相互作用产生了喷火器效应,导致了广泛的弧前火山活动和地壳的减弱,从而促进了边界地区所记录的独特变形方式,而这种变形方式在北美-太平洋板块边界的其他地方并没有出现过。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Oligocene and Miocene blowtorch volcanism within the California Borderland and its influence on the plate-boundary transition
The California Borderland is a uniquely broad and complex region of the North American−Pacific 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 American−Pacific plate boundary.
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