Harrats Volcanic Activity and Evolution of the Lithosphere-Asthenosphere Boundary beneath Western Saudi Arabia

这个项目着眼于沙特阿拉伯阿拉伯半岛一个神秘地区火山活动的原因。这一地区被称为麦加-麦地那-纳夫德线（MMN），是一系列小型到中型的火山区（称为“哈拉特”），从沙特阿拉伯、约旦和叙利亚的Read海向北延伸。该地区的火山活动发生在新近纪，最古老的火山活动发生在1000万年前，最年轻的火山活动发生在1256年（一次威胁到文化重要城市麦地那的喷发）。该项目旨在通过对喷发熔岩进行年代学、地球化学和岩石学研究，调查导致火山活动的岩浆活动的根本原因。该团队特别感兴趣的是大陆岩石圈（直接位于地壳下方的地幔上部刚性部分）和软流圈（对流的地幔下部较热的部分）在产生喷发的岩浆中的作用，以及这两个区域如何随时间和空间而变化。研究结果将对该地区的构造发展和火山活动所代表的灾害具有重要意义。沙特阿拉伯harrats是广泛的新近纪到现代大陆火山场位于阿拉伯半岛的西部部分。虽然大多数研究者认为哈拉特火山活动与红海的伸展和海底扩张有关，但岩浆活动的实际原因仍然不确定。该团队将通过研究选定的哈拉特来解决的关键问题是：（i）软流圈与岩石圈在大陆岩浆产生中的作用;（ii）融化深度和范围是否在空间和时间上发生系统性变化，以及这些变化与地球动力学背景的关系;以及（iii）地幔柱物质在哈拉特火山活动中的潜在作用。对这些地区进行的现代地球化学、岩石学或年代学研究很少。因此，他们的主要重点是获得40 Ar-39 Ar年龄，主要和微量元素浓度，Sr-Nd-Pb-He同位素组成和数据的熔融包裹体的良好的日期和代表性的样品套件从选定的harrats，代表了ESE-WNW横贯南北走向Makkah-Madinah-Nafud（MMN）火山线。他们还将使用一系列地球化学建模技术来调查岩浆沿着其横向流动的条件和来源，并研究熔融过程的时间变化。研究人员的最终目标是提供数据，使哈拉特火山活动能够更好地理解非洲-阿拉伯地区更广泛的地球动力学演变。

This project looks at the causes of volcanic activity within an enigmatic region of the Arabian Peninsula in Saudi Arabia. This region, known as the Makkah-Madinah-Nafud line (MMN) is a series of small to moderate size volcanic fields (known as 'harrats') that extend north from the Read Sea in Saudi Arabia, Jordan and Syria. Volcanism in this region has occurred in Neogene to recent times, with the oldest activity occurring starting more than 10 million years ago and the youngest occurred in 1256 (an eruption that threatened the culturally important city of Madinah. This project seeks to investigate the ultimate causes of the magmatic activity that lead to volcanism by use of geochronological, geochemical and petrological studies of erupted lavas. The team is specifically interested in the role of the continental lithosphere (the upper rigid portion of the mantle that directly underlies the crust) and asthenosphere (the underlying hotter portion of the mantle that convects) in producing erupted magmas and how these two regions might vary through time and space. The results of the study will have important implications for the tectonic development of this region and for the hazards represented by volcanic activity.The Saudi Arabian harrats are extensive Neogene to recent continental volcanic fields located in western portion of the Arabian Peninsula. Although most workers agree that Harrat volcanism is related to extension and sea floor spreading in the Red Sea in some way, the actual causes of magmatism remain uncertain. The key issues that this team will address via the study of selected harrats are: (i) the role of asthenosphere vs. lithosphere in the production of continental magmas; (ii) whether systematic changes in the depth and extent of melting occur in space and time, and the relation of these changes to geodynamic setting; and (iii) the potential role of mantle plume material in harrat volcanism. Little modern geochemical, petrological or geochronological study has been made of these areas. Thus their primary focus is to obtain 40Ar-39Ar ages, major and trace element concentrations, Sr-Nd-Pb-He isotope compositions and data for melt inclusions for well dated and representative samples suites from selected harrats that represent a ESE-WNW traverse across the north-south trending Makkah-Madinah-Nafud (MMN) volcanic line. They will also use a range of geochemical modeling techniques to investigate the conditions and sources of magmas along their traverse, and to study temporal changes in melting processes. The researchers' ultimate goal is to provide data that can allow harrat volcanism to be better understood in terms of broader geodynamic evolution of the Afro-Arabian region.