Sub-volcanic breccias: combining ore deposit, volcanology and geophysical perspectives

次火山角砾岩：结合矿床、火山学和地球物理观点

• 批准号: 2026583
• 金额: --
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2026583
• 关键词: Sub; volcanic; breccias; combining; ore

There is abundant evidence from exploration and mining of porphyry ore deposits that large (>100s of meters) pipes, dikes and irregular bodies of breccia form at kilometers depth, spatially and temporally associated with hydrous arc magmatic systems. This project will bring together the fields of economic geology, volcanology and geophysics, both to physically understand how the barren and mineralized breccias form, as well as to improve our interpretations of volcanic unrest signals recorded today.The classic paper on "Ore-related breccias in volcanoplutonic arcs" by Sillitoe (1985) compiles information on the size and geometry of breccia bodies, and lithologies, shape, size and vertical displacements of the constituent fragments. The properties of the sub-surface breccia bodies vary considerably (e.g. no vertical displacement of fragments to >1km displacement) and so there must be multiple mechanisms for their formation. The project will concentrate on breccias associated with sub-volcanic magmatic and hydrothermal processes that form by either release of hydrothermal fluids from magmas or from fragmentation and eruption of magmas from reservoirs. The physical modelling will consider evolving stresses in intrusions and surrounding rocks as volatile-saturated magmas are emplaced and crystallize, exsolving further volatiles, as well as stresses in rocks at depth induced by eruptions and dome/sector collapse (e.g. Montserrat; Druitt et al., 2002). All models, and hypotheses derived from them, will be constrained and tested by evidence from geology. A second strand of research will assess the expected monitoring signals (seismicity, ground deformation, gas emissions) that would be associated with the formation of breccias like those that have been uncovered by economic geologists. The flip side will be to review unrest signals from modern eruptive and noneruptive crises at volcanoes (e.g. Werner et al., 2011) and consider whether any might be related to processes equivalent to the deep brecciation events in the geological record.

从斑岩矿床的勘探和开采中，有大量证据表明，在千米深处形成的大型（10 ~ 100米）管、脉和角砾岩不规则体，在空间和时间上与含水弧岩浆系统有关。该项目将把经济地质学、火山学和地球物理学领域结合起来，从物理上理解贫瘠和矿化角砾岩是如何形成的，并改进我们对今天记录的火山动荡信号的解释。西利托（1985）的经典论文《火山-成矿弧中与矿石有关的角砾岩》汇编了角砾岩体的大小和几何形状，以及组成碎片的岩性、形状、大小和垂直位移等信息。地下角砾岩体的性质差异较大（如碎块垂直位移为0 ~ 10 km），因此它们的形成一定有多种机制。该项目将集中研究与次火山岩浆和热液过程有关的角砾岩，这些过程是由岩浆释放热液或由储层岩浆破碎和喷发形成的。物理模型将考虑随着挥发物饱和岩浆的就位和结晶，进一步溶解挥发物，侵入体和围岩中不断变化的应力，以及火山喷发和丘顶/部门崩塌引起的深部岩石应力（例如Montserrat； Druitt et al., 2002）。所有的模型，以及由此产生的假设，都将受到地质学证据的约束和检验。第二部分研究将评估预期的监测信号（地震活动、地面变形、气体排放），这些信号将与角砾岩的形成有关，就像经济地质学家发现的那样。另一方面，我们将回顾来自火山现代爆发和非爆发危机的动荡信号（例如Werner et al., 2011），并考虑是否有可能与地质记录中相当于深部角化事件的过程有关。