Geochemical and sedimentological evidence used to characterise supra-subduction spreading processes in the Izu-Bonin-Mariana forearc (IODP leg 352)

用于描述伊豆-小博南-马里亚纳弧前超俯冲扩张过程的地球化学和沉积学证据（IODP 第 352 段）

• 批准号: NE/M008193/1
• 负责人: Alastair Robertson
• 金额: $ 4.54万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FM008193%2F1
• 关键词: Geochemical; sedimentological; evidence; used; characterise

The planned work, which is directly in line with stated aims of IODP Leg 352, is to drill a section through the volcanic stratigraphy of the outer forearc of the Izu-Bonin-Mariana (IBM) system. The main aims are to better understand the processes of magmatism, tectonics and crustal accretion associated with subduction initiation. This, in turn, has implications for understanding the origin of the many ophiolites that are believed to form in this setting and so is a good opportunity to test the supra-subduction zone ophiolite model. Two sites in the Bonin forearc (BON-1 and BON- 2) form an offset-drilling pair that together should penetrate a full c.1.25 km lava section. Drilling this section will contribute to our understanding of intra-oceanic convergent plate margins by providing: 1) A high-fidelity record of magmatic evolution during subduction initiation; 2) A test of the hypothesis that "Fore-arc Basalts" (FAB) tholeiites lie beneath boninites;3) A record of the chemical gradients within these units and across their transitions; 4) Information on how mantle melting processes evolve during subduction initiation from early decompression melting of fertile asthenosphere to late flux melting of depleted mantle, providing key empirical constraints for realistic subduction initiation geodynamic models; and 5) A test of the hypothesis that forearc lithosphere created during subduction initiation is the birthplace of supra-subduction zone ophiolites. The applicant (A.H.F. Robertson) is sailing as a sedimentologist and, therefore, has responsibilities to study and interpret any sedimentary materials and so contribute to the overall objectives of the leg as far as possible. The proposed sedimentological and geochemical research should contribute directly to objectives 1,2,3 & 5 of the leg, as follows:Objective 1: A chemical record of the sediments recovered within and above the extrusive succession is directly relevant to the magmatic record during subduction initiation because this information can indicate chemical variability around the drill site, both locally (hundreds of metres) and more widely (kms to tens of kms);Objective 2: It will be important to determine the tholeiitic vs boninitic composition, in particular, of any interlava sediments as these may help to reveal the regional magmatic stratigraphy;Objective 3: The sediment composition will help determine whether the chemical gradients that are determined within the in situ igneous rocks are consistent on a regional scale.Objective 5: Sediments will be used to, in effect, map the region around the drill site and so contribute to an understanding of how sea floor develops in a supra-subduction zone setting. In addition, chemical study of sediments higher in the sequence above the basement will contribute information about the timing and composition of the earliest arc magmatism that follows the supra-subduction zone spreading phase. There may also be input from more remote locations; e.g. distant volcanic arc that may be detected by analysis of airfall volcanic glass (tephra). The applicant may contribute to this work, which will, however, be lead by the other shipboard sedimentologist, Stefan Kutterolf. The necessary information will be obtained by chemical, mineralogical and sedimentological observations and analyses which will mainly be carried out at the School of GeoSciences, University of Edinburgh. This work will involve chemical analysis by the XRF and ICPMS techniques, mineral analysis using XRD and electron probe and also volcanic glass analysis using the ion probe. The proposal supports a drilling expedition in which there is major UK involvement, including a UK Co-chief scientist and which builds on NERC investment in the SW Pacific region and comparable ophiolitic settings on land over many years. The work will involve collaboration with shipboard colleagues, especially Stefan Kuttterolf, the other sedimentologist.

计划中的工作直接符合国际大洋钻探计划第352航次的既定目标，即在伊豆-小笠原-马里亚纳（IBM）系统外弧火山地层中钻取一段。主要目的是更好地了解与俯冲开始有关的岩浆作用、构造和地壳增生过程。反过来，这对理解许多蛇绿岩的起源有影响，这些蛇绿岩被认为是在这种环境中形成的，因此是一个很好的机会来测试俯冲带上蛇绿岩模型。两个网站在小笠原弧（BON-1和BON- 2）形成一个偏移钻井对，一起应该穿透一个完整的c.1.25公里的熔岩部分。这一剖面的钻探将有助于我们对洋内会聚板块边缘的理解，因为它提供了：1）俯冲开始期间岩浆演化的高保真记录; 2）“弧前玄武岩”（FAB）拉斑玄武岩位于玻安岩之下的假设的检验;3）这些单元内部及其过渡段的化学梯度记录;（4）关于俯冲起始过程中地幔熔融过程如何从早期富营养软流圈减压熔融到晚期亏损地幔通量熔融演化的信息，为现实的俯冲起始地球动力学模型提供了关键的经验约束;（5）验证了俯冲启动过程中形成的弧前岩石圈是俯冲带上蛇绿岩的发源地的假说。 申请人（A.H.F.）Robertson）是作为一名沉积学家航行的，因此有责任研究和解释任何沉积材料，从而尽可能为该航段的总体目标做出贡献。拟议的沉积学和地球化学研究应直接促进专家组的目标1、2、3和5，具体如下：在喷出序列内和之上恢复的沉积物的化学记录与俯冲开始期间的岩浆记录直接相关，因为这些信息可以指示钻探地点周围的化学变化，本地（数百米）和更广泛的（公里至数十公里）;目标2：确定拉斑玄武岩与玻安岩的成分非常重要，特别是任何熔岩间沉积物的成分，因为这可能有助于揭示区域岩浆地层;目标3：沉积物成分将有助于确定在原地火成岩内确定的化学梯度在区域范围内是否一致。目标5：沉积物实际上将用于绘制钻探地点周围区域的地图，从而有助于了解海底在俯冲带上的发展情况。此外，对基底以上层序中较高位置的沉积物进行化学研究，将有助于提供有关超俯冲带扩张阶段之后最早期弧岩浆活动的时间和成分的信息。也可能有来自更远位置的输入;例如，可以通过分析空气降落的火山玻璃（火山灰）来检测的遥远火山弧。申请人可为这项工作作出贡献，但这项工作将由另一位船上沉积学家Stefan Kutterolf领导。 将主要在爱丁堡大学地球科学学院进行化学、矿物学和沉积学观测和分析，以获得必要的资料。这项工作将涉及使用X射线荧光和等离子体质谱技术进行化学分析，使用X射线衍射和电子探针进行矿物分析，以及使用离子探针进行火山玻璃分析。 该提案支持英国主要参与的钻探探险，其中包括英国联合首席科学家，并建立在西南太平洋地区的NERC投资和多年来陆地上的可比蛇绿岩环境的基础上。这项工作将涉及与船上同事的合作，特别是另一位沉积学家斯特凡·库特罗夫。

项目成果

Subduction initiation and ophiolite crust: new insights from IODP drilling

• DOI: 10.1080/00206814.2016.1276482
• 发表时间: 2017-01
• 期刊: International Geology Review
• 影响因子: 2.6
• 作者: M. Reagan;J. Pearce;K. Petronotis;R. Almeev;Aaron Avery;C. Carvallo;T. Chapman;G. Christeson

Tephrostratigraphy and Provenance From IODP Expedition 352, Izu‐Bonin Arc: Tracing Tephra Sources and Volumes From the Oligocene to Recent

• DOI: 10.1002/2017gc007100
• 发表时间: 2017-12
• 期刊: Geochemistry
• 影响因子: 3.7
• 作者: S. Kutterolf;J. Schindlbeck;A. Robertson;A. Avery;A. Baxter;K. Petronotis;K.‐L. Wang

Depositional setting, provenance, and tectonic-volcanic setting of Eocene–Recent deep-sea sediments of the oceanic Izu–Bonin forearc, northwest Pacific (IODP Expedition 352)

• DOI: 10.1080/00206814.2017.1393634
• 发表时间: 2018-11
• 期刊: International Geology Review
• 影响因子: 2.6
• 作者: A. Robertson;S. Kutterolf;Aaron Avery;A. Baxter;K. Petronotis;G. Acton;C. Carvallo;J. Schindlbeck