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首页> 外文期刊>Journal of Volcanology and Geothermal Research2012V243-244NOCT,15 >Eruptive history of the Ubehebe Crater cluster, Death Valley, California
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Eruptive history of the Ubehebe Crater cluster, Death Valley, California

机译：加利福尼亚死亡谷的Ubehebe火山口群的爆发历史

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A sequence of late Holocene eruptions from the Ubehebe Crater cluster in Death Valley was short-lived, emplacing several phreatomagmatic and magmatic deposits. Seven craters form the main group, which erupted along a north-south alignment 1.5 km long. At least five more make a 500-m east-west alignment west of the main crater group. One more is an isolated shallow crater similar to 400 m south of that alignment. All erupted through Miocene fanglomerate and sandstone, which are now distributed as comminuted matrix and lithic clasts in all Ubehebe deposits. Stratigraphic evidence showing that all Ubehebe strata were emplaced within a short time interval includes: (1) deposits from the many Ubehebe vents make a multi-package sequence that conformably drapes paleo-basement topography with no erosive gullying between emplacement units; (2) several crater rims that formed early in the eruptive sequence are draped smoothly by subsequent deposits; and (3) tack welded to agglutinated spatter and bombs that erupted at various times through the sequence remained hot enough to oxidize the overlying youngest emplacement package. In addition, all deposits sufficiently consolidated to be drilled yield reliable paleomagnetic directions, with site mean directions showing no evidence of geo-magnetic secular variation. Chemical analyses of juvenile components representing every eruptive package yield a narrow range in major elements [SiO2 (48.65-50.11); MgO (4.98-623); K2O (2.24-239)] and trace elements [Rb (28-33); Sr (1513-1588); Zr (373-404)]. Despite lithologic similarities, individual fall units can be traced outward from vent by recording layer thicknesses, maximum scoria and lithic sizes, and juvenile clast textural variations. This permits reconstruction of the eruptive sequence, which produced a variety of eruptive styles. The largest and northernmost of the craters, Ubehebe Crater, is the youngest of the group. Its largely phreatomagmatic deposits drape all of the others, thicken in paleogullies and thin over several newly created crater rims. Evidence in-hand virtually requires that the Ubehebe cluster of craters erupted over a brief time interval, not protracted over centuries. Published by Elsevier B.V.
机译：来自死亡谷的Ubehebe火山口群的一系列全新世晚期喷发是短暂的，形成了数个岩浆和岩浆沉积。七个陨石坑是主要的陨石坑，沿着1.5公里长的南北向爆发。至少有五个在主要火山口组以西500米的东西向对齐。再一个是孤立的浅坑，类似于该路线以南400 m。所有这些都是通过中新世的扇状沉积物和砂岩喷出的，现在它们以粉碎的基质和岩屑的形式分布在所有Ubehebe矿床中。地层学证据表明，所有Ubehebe地层都在短时间内被放置了，包括：（1）来自许多Ubehebe喷口的沉积物形成了一个多包裹层序，该层序一致地覆盖了古基底的地形，而在各沉积单元之间没有侵蚀性的沟壑； （2）在喷发序列的早期形成的多个火山口边缘被随后的沉积物平滑地包裹起来； （3）焊接到凝结的飞溅物上的大头钉和炸弹在整个序列中的不同时间喷出，炸弹仍然很热，足以氧化上面的最小的炸药包。此外，所有充分固结以待钻探的矿床都产生可靠的古磁方向，而站点平均方向没有显示出地磁长期变化的迹象。代表每个喷发物包的少年成分的化学分析显示，主要元素[SiO2（48.65-50.11）；氧化镁（4.98-623）; K 2 O（2.24-239）]和痕量元素[Rb（28-33）;高级（1513-1588）; Zr（373-404）]。尽管岩性相似，但仍可以通过记录层厚度，最大碎屑和岩性尺寸以及少年岩屑质地变化，从喷口向外追踪单个下降单元。这样可以重建喷发序列，从而产生各种喷发样式。火山口中最大和最北端的Ubehebe火山口是该火山口中最年轻的。它的大部分岩浆沉积物覆盖了所有其他沉积物，在古砾岩中变厚，并在几个新近形成的火山口边缘变薄。手中的证据实际上要求在短时间间隔内爆发Ubehebe火山口群，而不是持续几个世纪。由Elsevier B.V.发布

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