[Garbe-Schönberg] Understanding the crust-mantle transition from fast-spreading mid-ocean ridges: experiments and analytical studies using ICDP OmanDP drill core samples

German Title: Understanding the crust-mantle transition from fast-spreading mid-ocean ridges: experiments and analytical studies using ICDP OmanDP drill core samples

Abbreviation: 408

Current Status: approved


Main Applicant:Dr. Dieter Garbe-Schönberg


Resources Recipient

Prof. Dr. Francois Holtz
Prof. Dr. Jürgen Koepke


Other Persons

Samuel Müller
Dominik Mock


Conveyor Begin: 1 April, 2020
Conveyor End: 31 March, 2023
Conveyor Duration: 36
Year: 2020


Description

In winter 2017/18, the ICDP drilling initiative "Oman Drilling Project" (OmanDP) successfully penetrated the paleo-crust-mantle transition of the Oman ophiolite, which is  regarded as the world’s largest, bestexposed, and most-studied section of subaerially exposed oceanic lithosphere. The cores are 400 m (CM1) and 300 m (CM2) long and  were recovered with a nearly 100 % success rate, making them a uniquely valuable resource for petrographical, petrological, and geochemical study and ensuring access to coherent sections throughout the enigmatic transition between the uppermost mantle and the lowermost crust of fast-spreading ridge systems. The drilled transects through  the crust-mantle transition of the Oman paleo-crust, provide coherent long sections of the lowermost layered gabbros, massive dunites, troctolites, and wehrlites without any  gaps, and can be regarded as a Rosetta Stone for understanding the magmatic processes and the mode of deep crustal accretion, in a depth window that was not accessible  in recent oceans so far. The proposed project focuses on several scientific targets following two different methodological approaches: (1) In an experimental study we aim to  simulate equilibrium and fractional crystallization in a parental MORB-type system relevant for a setting of initiation of a subduction zone at the transition between "dry" (like  East Pacific Rise) and "wet" conditions (Izu‐Bonin‐Mariana arc-type crust). In a subproject we aim to quantify the trace element distribution between spinel/chromite and  MORB melt. (2) The second approach focus on petrological and geochemical investigations on the rocks from the CM1 and CM2 drill cores in order to clarify the mechanism  of massive dunite formation in the crust-mantle transition, and establish the exact mode of differentiation/fractionation within the lowermost crust. The results of both  complementary approaches will provide a basis for a deep understanding of the magmatic processes at the base of fast-spreading crust in an environment of initial  subduction, and will provide fundamental knowledge about the geodynamics of accretion of fast-spreading oceanic crust.