Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA
Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA
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美国西部爱达荷州斯内克河平原海斯火山场的时间和发育
DOI：
10.1130/b25519.1
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发表时间：
2005
影响因子：
4.9
通讯作者：
W. Mcintosh
中科院分区：
文献类型：
--
作者：
L. Morgan;W. Mcintosh
蛇河平原（Snake River Plain， SRP）在过去16 Ma作为一个双峰火山省发展，以响应北美板块在固定融化异常上的西南运动。沿SRP的火山活动主要是爆炸性高硅流纹岩的喷发，这是已知的一些最大的喷发。玄武岩喷发代表了火山作用的最后阶段，在大量流纹岩矿床之上形成了一层薄薄的盖层。火山活动一般从西向东，沿着平原断断续续地在连续的火山场中进行，这些火山场由巢状的火山口复合体组成，在大约0.5-1 Ma的特定区域内形成主要的火山口喷发，类似于今天的黄石高原火山场，并与之延续。在特定的时间和空间点上，北美板块通过熔融异常，伴随着隆起、区域构造运动、大规模爆发和火山口沉降，随后是玄武岩火山作用和普遍沉降。爱达荷州SRP东部的Heise火山场代表了紧邻黄石高原火山场西南的一个毗邻且稍老的火山场。5块大体积（> ~ 0.5 km 3）流纹岩火成岩构成了研究区晚中新世至上新世早期火山活动的时间地层格架。野外关系和高精度的40 Ar/ 39 Ar年龄测定表明，这些区域的4块火成岩是从海泽火山场喷发出来的，形成了海泽群的框架。这些是Blacktail Creek凝灰岩（6.62 ' 0.03 Ma）， Walcott凝灰岩（6.27 ' 0.04 Ma）， Conant Creek凝灰岩（5.51 ' 0.13 Ma）和Kilgore凝灰岩（4.45 ‘ 0.05 Ma，所有误差报告在’ 2a）。该地区第五个广泛分布的褐煤是星光组（10.21 ' 0.03 Ma）的Arbon Valley凝灰岩，它是从Heise火山场外的一个火山口喷发出来的。这些结果确定了Conant Creek凝灰岩在Heise火山场中是一种独特且广泛分布的烟灰岩，消除了以前由于K/Ar和裂变径迹日期不一致而造成的混淆。新的40ar / 39ar测定，结合地球化学、岩性、地球物理和野外资料，确定了Heise火山场及其周边地区的火山和构造历史。Heise火山场喷发的火山单元也为晚新生代Snake山脉的伸展和怀俄明州Teton山脉的隆起等构造事件提供了时间控制。在Snake山脉，Heise地块以东50公里处的大型（≥0.10 km 3）密西西比河石灰岩滑块的运动发生在6.3 - 5.5 Ma之间，可能是由5.51 ' 0.13 Ma Conant Creek凝灰岩的破火山口喷发造成的。这个垂直移动约300米的滑块表明Snake山脉至少有5.5 Ma的显著起伏。在Jackson Hole，与SRP东部Heise火山场Kilgore火山口喷发有关的4.45′0.05 ma Kilgore凝灰岩流出相的分布表明，此时北提顿山脉并不是一个重要的地形特征。
The Snake River Plain (SRP) developed over the last 16 Ma as a bimodal volcanic province in response to the southwest movement of the North American plate over a fixed melting anomaly. Volcanism along the SRP is dominatedby eruptions of explosive high-silica rhyolites and represents some of the largest eruptions known. Basaltic eruptions represent the final stages of volcanism, forming a thin cap above voluminous rhyolitic deposits. Volcanism progressed, generally from west to east, along the plain episodically in successive volcanic fields comprised of nested caldera complexes with major caldera-forming eruptions within a particular field separated by ca. 0.5-1 Ma, similar to, and in continuation with, the present-day Yellowstone Plateau volcanic field. Passage of the North American plate over the melting anomaly at a particular point in time and space was accompanied by uplift, regional tectonism, massive explosive eruptions, and caldera subsidence, and followed by basaltic volcanism and general subsidence. The Heise volcanic field in the eastern SRP, Idaho, represents an adjacent and slightly older field immediately to the southwest of the Yellowstone Plateau volcanic field. Five large-volume (>0.5 km 3 ) rhyolitic ignimbrites constitute a time-stratigraphic framework of late Miocene to early Pliocene volcanism for the study region. Field relations and high-precision 4 0 Ar/ 3 9 Ar age determinations establish that four of these regional ignimbrites were erupted from the Heise volcanic field and form the framework of the Heise Group. These are the Blacktail Creek Tuff (6.62 ′ 0.03 Ma), Walcott Tuff (6.27 ′ 0.04 Ma), Conant Creek Tuff (5.51 ′ 0.13 Ma), and Kilgore Tuff (4.45 ′ 0.05 Ma; all errors reported at ′ 2a). The fifth widespread ignimbrite in the region is the Arbon Valley Tuff Member of the Star-light Formation (10.21 ′ 0.03 Ma), which erupted from a caldera source outside of the Heise volcanic field. These results establish the Conant Creek Tuff as a distinct and widespread ignimbrite in the Heise volcanic field, eliminating former confusion resulting from previous discordant K/Ar and fission-track dates. New 4 0 Ar/ 3 9 Ar determinations, when combined with geochemical, lithologic, geophysical, and field data, define the volcanic and tectonic history of the Heise volcanic field and surrounding areas. Volcanic units erupted from the Heise volcanic field also provide temporal control for tectonic events associated with late Cenozoic extension in the Snake Range and with uplift of the Teton Range, Wyoming. In the Snake Range, movement of large (≥0.10 km 3 ) slide blocks of Mississippian limestone exposed 50 km to the east of the Heise field occurred between 6.3 and 5.5 Ma and may have been catastrophically triggered by the caldera eruption of the 5.51 ′ 0.13-Ma Conant Creek Tuff. This slide block movement of ∼300 vertical meters indicates that the Snake Range had significant relief by at least 5.5 Ma. In Jackson Hole, the distribution of outflow facies of the 4.45 ′ 0.05-Ma Kilgore Tuff related to eruption from the Kilgore caldera in the Heise volcanic field on the eastern SRP indicates that the northern Teton Range was not a significant topographic feature at this time.