澳大利亚昆士兰地质调查局Tapu, A. T.的课题组认为火山的岩浆结构沿着逐渐减弱的热点变得更加复杂。该项研究成果发表在2023年3月23日出版的《自然—地球科学》上。
研究小组将地球最长的大陆热点链-矿物学、岩石学和地质年代学结合起来，评估减弱的地幔柱强度对岩浆柱通量和喷发前岩浆运输和储存。该团队聚集于新生代澳大利亚东部的年龄递增的火山，被分为板块运动变化和大量的火山活动。北部火山更老，寿命更长(3.5-7百万年(Ma))，喷发了大量(大于800 立方千米)的双峰式岩浆(玄武岩和流纹岩)，产生均质，贫乏晶体的玄武岩(大约百分之3 vol 的斑晶)。南部火山较小(小于300立方千米)，寿命较短(≤1.5个百万年 )，分裂成两条平行的轨迹，喷发出演化程度更高，结构更复杂的岩浆(约百分之12 vol 的斑晶，内部分区)。
研究发现暗示了岩浆通量的减弱，使得供给系统日益复杂，从而增强了岩浆的储存和分化。类似的趋势在全球热点跟踪表明，羽流通量和岩浆通量在板内火山的演化中起到至关重要的作用。
据介绍，地幔柱是构造板块内是火山活动的关键驱动力。在地幔柱寿命期内，预计地幔柱流量以及由此产生的岩浆通量会发生变化，但它们对火山结构和喷发物及风格的影响仍然很少受到限制。
附：英文原文
Title: Increasing complexity in magmatic architecture of volcanoes along a waning hotspot
Author: Tapu, A. T., Ubide, T., Vasconcelos, P. M.
Issue&Volume: 2023-03-23
Abstract: Mantle plumes are key drivers of volcanism within tectonic plates. Variations in plume flux and the resulting magma flux are expected within a plume’s lifetime, but their impact on volcanic architecture and eruption products and styles remains poorly constrained. Here we combine mineralogy, petrology and geochronology of Earth’s longest continental hotspot chain to assess the effects of waning plume strength on magma flux and pre-eruptive magma transport and storage. We focus on Cenozoic age-progressive volcanoes across eastern Australia, divided by a change in plate motion and voluminous volcanism. Northern volcanoes are older and ‘long-lived’ (3.5–7 million years (Ma)) and erupted high volumes (>800km3) of bimodal magmas (basalts and rhyolites), producing homogeneous, crystal-poor basalts (~3 vol% phenocrysts). Southern volcanoes are smaller (<300km3), ‘short-lived’ (≤1.5Ma) and split into two parallel tracks that erupted more evolved and texturally complex magmas (~12 vol% phenocrysts, internally zoned). These findings imply waning magma flux leads to increasingly complex feeder systems that enhance magma storage and differentiation. Similar trends in hotspot tracks globally suggest that plume and magma flux play a crucial role in the evolution of intraplate volcanoes.
DOI: 10.1038/s41561-023-01156-9
Source: https://www.nature.com/articles/s41561-023-01156-9