A Study of Recently Uplifted Upper Mantle and Lower Crustal Sections from the Red Sea: Implications for Rifting and the Opening of Oceans

对红海最近隆起的上地幔和下地壳部分的研究：对裂谷和海洋开放的影响

• 批准号: 8816948
• 负责人: Enrico Bonatti
• 金额: --
• 依托单位: Columbia University Lamont Doherty Earth Observatory
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-07-01 至 1992-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8816948&HistoricalAwards=false
• 关键词: Study; Recently; Uplifted; Upper; Mantle

This project is to study a section of upper mantle peridotites and a lower crustal granulite-facies complex exposed on the island of Zabargad, Red Sea, as part of a continuing study on the evolution of the upper mantle and lower crust as continental rifts evolve to oceanic rifts.The crustal complex contain garnet- granulite-facies silicic gneisses, and amphibolitized metagabbros and metapyroxenites. The silicic gneisses are probably remnants of the pre-rift ;lower continental crust formed ;during the Pan African cycle. The high-P meta-igneous rocks are interpreted as metamorphosed basic magmas that underplated the crust prior to and during rifting. the peridotites include isotopically depleted spinel lherzolites that were partially hydrated to amphibole peridotites by fluids with the isotopic signature (low 87Sr/86Sr and 143Nd/144Nd) of subcontinental mantle metasomatism. They are believed to have been part of the sub-Red Sea mantle. Both the crustal complex and the peridotites show successive re- equilibration assemblages from granulite to amphibolite to greenschist facies conditions suggesting they were uplifted together from deep tectonic levels. The PIs will test the hypothesis that the entire section was once very close to the base of the Pan African crust and was raised and exposed recently and rapidly, possibly along a major detachment fault that may be exposed on Zabargad, as a result of the opening of the Red Sea. Schedule for study are petrology, major, trace and Ree elements, mineral chemistry, and Sr, Nd, Pb and possibly Os isotopes of the Zabargad peridotites and crustal rocks. A major goal will be to determine initial ages, recrystallization ages and uplift rates of the crustal rocks. Rb-Sr, Sm-Nd and U-Pb whole-rock and mineral results from Lamont-Doherety Geological Observatory will be coordinated with U-Pb zircon, 40Ar/39Ar amphibole, and zircon, sphene and apatite fission track ages from other laboratories. The objectives are (a) to determine the time, rate and mechanism of uplift of the Zabargad complex, (b) define the nature of the lower continental crust in a transitional rift, (c) investigate the processes of underplating in a pre-oceanic rift, (d) clarify the petrological and geochemical evolution of the crust and mantle in a major rift prior to sea floor spreading, and (e) infer whether "active" or "passive" rifting prevailed in the Red Sea Rift. The results expected from this project will help us understand the crustal evolution of Atlantic-type passive margins.

该项目是研究上地幔橄榄岩的一部分，以及在红海扎巴尔加德岛上暴露于扎巴尔加德岛上的下地壳颗粒质面，作为对上地幔和下地壳的持续研究的一部分，大陆裂口随着大陆裂谷的发展，随着海洋裂谷的进化，含有海洋裂谷。梅糖替代人。硅质片麻岩可能是前裂的残留物；在泛非洲周期中形成的下大陆壳。高-P元尊敬的岩石被解释为变形的基本岩浆，在裂谷之前和裂谷过程中低估了地壳。橄榄岩包括同位素耗尽的紫杉醇，通过具有同位素特征（低87SR/86SR和143nd/144nd）的流体将部分水合到闪石橄榄岩中，并将其亚the子的属于亚the子的甲坦体底层底层底层底部底层质量质量。据信它们是红色海底的一部分。地壳复合物和橄榄岩都表现出从颗粒状到闪石再到绿岩相的条件的连续平衡组合，这表明它们是从深层构造水平上升高的。 PI将检验以下假设：整个部分曾经非常接近泛非洲地壳的底部，并且由于红海的开放而导致了最近，迅速地抬高和迅速暴露，可能沿着扎巴尔加德的主要脱离断层。研究时间表是岩石学，主要，痕量和REE元素，矿物化学和SR，ND，PB，以及Zabargad橄榄岩和地壳岩石的OS同位素。一个主要目标是确定地壳岩石的初始年龄，重结晶年龄和提升率。 RB-SR，SM-ND和U-PB的全摇滚和Lamont-Doherety地质观测站的矿物质结果将与其他实验室的U-PB锆石，40AR/39AR闪石以及氧化锆，Sphene和Apatite裂变田径相协调。目的是（a）确定扎巴尔加德复合综合体的上升的时间，速率和机制，（b）定义了过渡性裂痕中下大陆壳的性质，（c）调查在海洋前裂谷中低估的过程，（d）（d）澄清岩石学和cressiallogical and Geochemical Exertolution and cortive and cortive corkity and cortive and cortive and cortion and core and Maid riff of coprif and Maid riff of（'红海裂谷占了上风。该项目的预期结果将有助于我们了解大西洋型被动利润率的地壳演变。