Submarine sliver in North Kona: A window into the early magmatic and growth history of Hualalai Volcano, Hawaii
Submarine sliver in North Kona: A window into the early magmatic and growth history of Hualalai Volcano, Hawaii
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DOI：
10.1016/j.jvolgeores.2005.07.028
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发表时间：
2006-03-01
影响因子：
2.9
通讯作者：
Kimura, J
中科院分区：
文献类型：
--
作者：
Hammer, JE;Coombs, ML;Kimura, J
在2002年的一次JAMSTEC巡航中，两个载人潜水器检查了华拉莱西北裂谷带和一个拉长的山脊，山脊高达3900 Mbsl。潜水点S690(水深3412-2104m)的裂谷带两侧覆盖着拉长和截断的枕状熔岩。这些富含橄榄石的拉斑玄武岩在成分上与沿板凳进一步向南检测的那些熔岩没有什么区别，只是它们的溶解硫含量范围更广(200-1400ppm)。在S692潜水中研究的细长山脊，位于台阶底部，是一组不同的岩性单元，包含火山碎屑物质、玻璃枕状角砾岩和熔岩块；这些单元包含一系列成分，包括拉斑玄武岩、过渡玄武岩和夏威夷岩。拉长海脊内物质的结构、成分和地层关系要求多种传输机制将多次喷发的物质并列到单独的岩层中，将它们压实成一个连贯的单元包，并将其带到距离北科纳滑塌台地边缘10公里的今天的深度。在拉长海脊底部的富硫夏威夷玻璃可能是华莱幼年碱性火山作用的第一个现存代表。它们在地球化学上不同于屏蔽拉斑玄武岩和屏蔽后碱性岩浆，但可能与单斜辉石高压结晶分馏的过渡性玄武岩有关。构成露头的大部分的玄武岩玻璃与莫纳克亚拉斑玄武岩和其他华拉莱拉斑玄武岩相似，但它们与年轻的玄武岩不同之处在于具有较大的不相容元素丰度和较高的CaO。这些差异可能是由碱性岩浆向屏蔽期岩浆转变过程中的小范围部分熔融造成的。大多数火山碎屑拉斑玄武岩的硫含量较低，表明相对于斜坡中部滑塌台地的发育，华拉莱早在海平面以上出现。(C)2005 Elsevier B.V.保留所有权利。
Two manned submersible dives examined the Hualalai Northwest rift zone and an elongate ridge cresting at 3900 mbsl during a 2002 JAMSTEC cruise. The rift zone flank at dive site S690 (water depth 3412-2104 m) is draped by elongated and truncated pillow lavas. These olivine-rich tholeiitic lavas are compositionally indistinguishable from those examined further south along the bench, except that they span a wider range in dissolved sulfur content (200-1400 ppm). The elongate ridge investigated in dive S692, located at the base of the bench, is a package of distinct lithologic units containing volcaniclastic materials, glassy pillow breccias, and lava blocks; these units contain a range of compositions including tholeiitic basalt, transitional basalt, and hawaiite. The textures, compositions, and stratigraphic relationships of materials within the elongate ridge require that a variety of transport mechanisms juxtaposed materials from multiple eruptions into individual beds, compacted them into a coherent package of units, and brought the package to its present depth 10 km from the edge of the North Kona slump bench.Sulfur-rich hawaiite glasses at the base of the elongate ridge may represent the first extant representatives of juvenile alkalic volcanism at Hualalai. They are geochemically distinct from shield tholeiite and post-shield alkalic magmas, but may be related to transitional basalt by high-pressure crystal fractionation of clinopyroxene. Tholeiitic glasses that compose the majority of the exposed outcrop are similar to Mauna Kea tholeiites and other Hualalai tholeiites, but they differ from younger basalts in having greater incompatible element enrichments and higher CaO for a given MgO. These differences could arise from small extents of partial melting during the transition from alkalic to shield stage magmatism. Low sulfur contents of most of the volcaniclastic tholeiites point to early emergence of Hualalai above sea level relative to the development of the midslope slump bench. (c) 2005 Elsevier B.V. All rights reserved.