Constraining the Early Eruptive History of the Mono Craters Rhyolites, California, Based on 238U‐230Th Isochron Dating of Their Explosive and Effusive Products
Constraining the Early Eruptive History of the Mono Craters Rhyolites, California, Based on 238U‐230Th Isochron Dating of Their Explosive and Effusive Products
复制标题
基于其爆炸和喷发产物的 238U‐230Th 等时线测年，限制加利福尼亚州莫诺陨石坑流纹岩的早期喷发历史
DOI：
10.1029/2018gc008052
复制
发表时间：
2019
期刊：
影响因子：
3.7
通讯作者：
Jonathan S. Miller
中科院分区：
文献类型：
--
作者：
M. Marcaida;J. Vazquez;M. Stelten;Jonathan S. Miller
莫诺火山口是位于加州中东部莫诺湖南部的至少28个圆顶和峡谷的重叠链，代表了莫诺湖-长谷火山地区最近的高硅流纹岩岩浆喷发。区域性广泛分布的火山灰瀑布沉积物从莫诺火山口作为重要的年代地层学标志，在美国西部的晚第四纪陆地档案的相关性。因此，莫诺火山口的喷发年表不仅对火山灾害的考虑至关重要，而且对古气候和古地磁研究也至关重要。在这里，我们使用离子微探针238 U-230 Th对自晶锆石和褐帘石微斑晶的未抛光晶面进行定年，从而限制了莫诺火山口早期火山活动的时间，这些微斑晶对喷发前结晶的最后阶段进行了取样。地层学上最古老的圆顶（含黑云母的流纹岩）产生的238 U-230 Th等时线年龄介于约1000年至约2000年之间。42、你通过238 U-230 Th地质年代学和钛磁铁矿地球化学的耦合，明确地与祖先莫诺湖威尔逊溪地层中的定年火山岩有关。第二古老的圆顶（含斜方辉石流纹岩）具有重叠的238 U-230 Th等时线年龄，其不确定性在已发表的含铁橄榄石流纹岩圆顶的K/Ar和40 Ar/39 Ar年龄范围内，表明更新世-全新世边界附近的莫诺火山口有一段强烈的喷发活动。我们新的和以前公布的威尔逊溪地层中的火山岩的238 U-230 Th年龄为威尔逊溪地层中记录的有争议的地磁漂移提供了强大的地质年代学约束。
The Mono Craters are an overlapping chain of at least 28 domes and coulees located south of Mono Lake, east central California, and represent the most recent eruptions of high‐silica rhyolite magma in the Mono Lake‐Long Valley volcanic region. Regionally widespread tephra fall deposits from the Mono Craters serve as important chronostratigraphic markers for correlations of late Quaternary terrestrial archives in the western United States. A well‐resolved eruption chronology for the Mono Craters is thus not only critical for volcanic hazard considerations but also for paleoclimatic and paleomagnetic studies. Here we constrain the timing of early Mono Craters volcanism using ion microprobe 238U‐230Th dating of unpolished crystal faces of autocrystic zircon and allanite microphenocrysts, which samples the final stage of crystallization prior to eruption. The stratigraphically oldest domes (biotite‐bearing rhyolites) yield 238U‐230Th isochron dates between ca. 42 and ca. 19 ka and are unambiguously linked to dated tephras in the Wilson Creek formation of ancestral Mono Lake via coupled 238U‐230Th geochronology and titanomagnetite geochemistry. The second oldest set of domes (orthopyroxene‐bearing rhyolites) have overlapping 238U‐230Th isochron dates that are within uncertainty of published K/Ar and 40Ar/39Ar dates for the fayalite‐bearing rhyolite domes, suggesting a period of intense effusive activity for the Mono Craters near the Pleistocene‐Holocene boundary. Our new and previously published 238U‐230Th dates for tephras in the Wilson Creek formation provide robust geochronologic constraints for the controversial geomagnetic excursion recorded in the Wilson Creek formation.
影响因子：
3.5
作者：
A. Schmitt;M. Danišík;N. Evans;W. Siebel;Elena Kiemele;F. Aydın;Janet Harvey
通讯作者：
A. Schmitt;M. Danišík;N. Evans;W. Siebel;Elena Kiemele;F. Aydın;Janet Harvey