Kelyphite textures experimentally reproduced through garnet breakdown in the presence of a melt phase
Kelyphite textures experimentally reproduced through garnet breakdown in the presence of a melt phase
复制标题
DOI：
10.1093/petrology/egac110
复制
发表时间：
2022-10
影响因子：
3.9
通讯作者：
I. Ezad;D. Dobson;A. Thomson;E. Jennings;S. Hunt;J. Brodholt
中科院分区：
文献类型：
--
作者：
I. Ezad;D. Dobson;A. Thomson;E. Jennings;S. Hunt;J. Brodholt
在石榴石破裂过程中形成的复杂的多相反应边缘被称为Kelyphite Coronae，在折返的地幔捕虏体中很常见。长期以来，人们已经确定，石榴石和橄榄石的反应产生由尖晶石和辉石组成的黄长石冠，高压石榴石核心的保存需要足够快的提升材料通过尖晶石二辉橄榄岩稳定场从至少60公里的深度。我们提出了新的高压，高温实验中的石榴石击穿尖晶石二辉橄榄岩的稳定性领域证明了一系列的级联反应可以重现自然界中看到的多层，多相的Kelyphites。在所有的实验中，发生故障，熔体似乎已经缓和了反应走向平衡，我们相信这是第一次实验证实这种熔体在石榴石击穿反应的重要性。在我们的实验中，至少有三个不同的区域的同心kelyphite生长可以发生在一个单一的压力，温度条件下，我们建议，因此，这样的kelyphite在天然样品中看到的不一定是由一个多阶段的隆起路径，通常假设。石榴石周围的Kelyphitic冠以前曾被用来估计隆起率，然而，缺乏动力学数据的相关折返反应限制了他们的使用PTT途径估计和了解侵位机制。为了限制准确的PTT途径，我们使用反应边缘厚度作为反应进展的代理，并提出了石榴石击穿动力学的初步结果。
Complex multiphase reaction rims that form during garnet breakdown are known as kelyphite coronae and are common amongst exhumed mantle xenoliths. It has long been established that a reaction of garnet and olivine produces kelyphite corona consisting of spinel and pyroxenes, and that preservation of high-pressure garnet cores requires sufficiently rapid uplift of material through the spinel lherzolite stability field from depths of at least 60 km. We present new high-pressure, high-temperature experiments of garnet breakdown in the spinel-lherzolite stability field demonstrating that a series of cascading reactions can reproduce the multilayer, multiphase kelyphites seen in nature. In all experiments where breakdown occurred, a melt appears to have moderated the reactions towards equilibrium; we believe this to be the first experimental confirmation of the importance of such melts in garnet breakdown reactions. In our experiments at least three distinct zones of concentric kelyphite growth can occur at a single pressure, temperature condition; we suggest, therefore, that such kelyphites seen in natural samples do not have to be caused by a multistage uplift path as is often assumed. Kelyphitic coronae surrounding garnet have previously been used to estimate uplift rates, however, the lack of kinetic data for relevant exhumation reactions has limited their use for PTt pathway estimations and the understanding of emplacement mechanisms. In order to constrain accurate PTt pathways we use reaction rim thickness as a proxy for reaction progress and present preliminary results for the kinetics of garnet breakdown.