近日，美国地质调查局Peter W. Lipman报道了一个大型凝灰岩破火山口沉降引起的早期隆起。相关论文于2024年4月5日发表于国际顶尖学术期刊《地质学》杂志上。

研究人员称，随着破火山口的消退，在厚堆积的熔结凝灰岩中形成了一个明确的拱形或圆顶结构，记录了破火山口填充时楔状断层的生长，早期喷发凝灰岩的流变作用和局部底辟活动，上部焊接带倾角减小以及晚期喷发英安岩相楔入生长中的圆顶侧翼。

早期沉降引起的隆起可能是由以下因素触发的：沿环断层喷口的岩浆优先下降，相对不渗透的泡状形成和不同的岩浆差异浮力，破火山口边缘的山体滑坡以及破火山口壁堆积体的外围载荷或某些因素的组合。破火山口隆起的早期形成对岩浆撤退模式，和未喷发岩浆的残余成分梯度具有重要意义。

据悉，许多有充分记录的再生火山口的隆起是在相关的熔结凝灰岩喷发完成后才开始的，但在科罗拉多州（美国）南落基山火山区的大型破火山口的拱起是在喷发期间开始的。

附：英文原文

Title: Subsidence-induced early doming at a large ignimbrite caldera

Author: Peter W. Lipman

Issue&Volume: 2024-04-05

Abstract: Uplift at many well-documented resurgent calderas started only after completion of the associated ignimbrite eruption, but arching of the large Bachelor caldera in the Southern Rocky Mountain volcanic field, Colorado (USA), began during the eruption. A well-defined arched or domical structure, initiated within thickly accumulating ignimbrite as the caldera subsided, is documented by growth of keystone faults as the caldera filled, rheomorphism and local diapiric mobilization of early-erupted tuff, decreased dips in upper welding zones, and wedging of a late-erupted dacitic phase against flanks of the growing dome. Early subsidence-induced doming may have been triggered by preferential magma draw-down along ring-fault vents, relatively impermeable vesiculation and differential magma buoyancy centrally within the caldera, peripheral loading at caldera margins by landslides and talus from caldera walls, or some combination of factors. Early inception of caldera doming has implications for models of magma withdrawal and residual compositional gradients in non-erupted magma.

DOI: 10.1130/G52130.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52130.1/637513/Subsidence-induced-early-doming-at-a-largeredirectedFrom=fulltext