Generation of Silicic Melts in the Early Izu-Bonin Arc Recorded by Detrital Zircons in Proximal Arc Volcaniclastic Rocks From the Philippine Sea
Generation of Silicic Melts in the Early Izu-Bonin Arc Recorded by Detrital Zircons in Proximal Arc Volcaniclastic Rocks From the Philippine Sea
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DOI：
10.1002/2017gc006948
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发表时间：
2017-10-01
影响因子：
3.5
通讯作者：
Shukle, J. T.
中科院分区：
文献类型：
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作者：
Barth, A. P.;Tani, K.;Shukle, J. T.
在国际海洋发现计划351-U1438站点的1.2 km厚的古近纪火山岩剖面保存了伊豆-小笠原洋弧形成的深海近端记录，以及沿着九州-帕劳海岭（KPR）的火山演化。从火山岩砂岩中回收的锆石的Pb/U年龄和微量元素组成保存了一个显着的幼年岛弧演化的时间记录。在北方KPR的一个或多个活动弧体中，Pb/U年龄范围为43 ~ 27 Ma，与物源一致。高浓度的选定的微量元素的丰度提供洞察U1438碎屑锆石主机熔体的成因，并代表在电弧设置熔体成分的短期和长期变化的有用指标。该网站U1438锆石跨越洋中脊辉长岩和相对丰富的大陆弧，从一个原始的大洋弧设置来自一个高度亏损的地幔源的熔体预测的锆石之间的成分范围。熔融锆石的饱和温度和钛锆石测温表明，在相对凉爽的起源，并随着时间的推移，向更多的Th和U丰富的组合物的熔体。Th，U，和轻稀土元素富集开始约35马是一致的碎屑锆石记录区域弧不对称和选择性微量元素富集后弧弧熔融的少年伊豆-小笠原arc.Plain语言摘要俯冲构造板块如何开始，以及如何在海底形成新的爆炸性火山的过程？了解这些重要地质过程的早期阶段具有挑战性，因为它们的岩石记录通常隐藏在较年轻的岩石和沉积物之下。国际海洋发现计划第351远征队开始回答这些问题，从菲律宾海底下恢复了一个连续的1.6公里长的岩心，其中包含这些地质事件的岩石记录。在探险过程中从海底深处回收的沉积岩保存了一个新的俯冲带上方海底火山的显着记录。这些沉积物中矿物的放射性同位素和微量元素揭示了长达1500万年的爆炸性海底火山的生长和演变。
A 1.2 km thick Paleogene volcaniclastic section at International Ocean Discovery Program Site 351-U1438 preserves the deep-marine, proximal record of Izu-Bonin oceanic arc initiation, and volcano evolution along the Kyushu-Palau Ridge (KPR). Pb/U ages and trace element compositions of zircons recovered from volcaniclastic sandstones preserve a remarkable temporal record of juvenile island arc evolution. Pb/U ages ranging from 43 to 27 Ma are compatible with provenance in one or more active arc edifices of the northern KPR. The abundances of selected trace elements with high concentrations provide insight into the genesis of U1438 detrital zircon host melts, and represent useful indicators of both short and long-term variations in melt compositions in arc settings. The Site U1438 zircons span the compositional range between zircons from mid-ocean ridge gabbros and zircons from relatively enriched continental arcs, as predicted for melts in a primitive oceanic arc setting derived from a highly depleted mantle source. Melt zircon saturation temperatures and Ti-in-zircon thermometry suggest a provenance in relatively cool and silicic melts that evolved toward more Th and U-rich compositions with time. Th, U, and light rare earth element enrichments beginning about 35 Ma are consistent with detrital zircons recording development of regional arc asymmetry and selective trace element-enriched rear arc silicic melts as the juvenile Izu-Bonin arc evolved.Plain Language Summary How does subduction of tectonic plates begin, and how does this process lead to the formation of new explosive volcanoes on the sea floor? Understanding the early stages of these important geologic processes is challenging, because their rock record is usually hidden, buried deep beneath younger rock and sediment. International Ocean Discovery Program Expedition 351 set out to answer these questions by recovering a continuous, 1.6 km long drill core from beneath the Philippine Sea floor that contains a rock record of these geologic events. Sedimentary rocks recovered from deep below the sea floor during the expedition preserve a remarkable record of submarine volcanoes above a new subduction zone. Radioactive isotopes and trace elements in minerals from these sediments reveal a 15 million year-long account of the growth and evolution of explosive submarine volcanoes.