Geological Society of America

T128 Unravelling Timescales of Magmatism, Metamorphism, and Crustal Evolution II

Monday, 16 October 2023
1:30 PM - 5:30 PM
327

NOT ALL S-TYPE GRANITES ARE CREATED EQUAL

Paper number: T128-2
Program: Technical Sessions
Time: 1:40 PM – 1:55 PM

Authors

Chris Spencer Presenting Author
Queen’s University, Kingston, ON
Clare Warren
The Open University, Milton Keynes
Nicholas Roberts
British Geological Survey, Keyworth
Claire Bucholz
California Institute of Technology, Pasadena, CA
Tiago Angelo
Queen’s University, Kingston, ON
Shaoxiong He
Queen’s University, Kingston, ON
Charlie Oldman
Open University, Milton Keynes
Janne Liebmann
Curtin University, Perth
Guimei Lu
Guangzhou Institute of Geochemistry, Guangzhou
Jiyuan Yin
Chinese Academy of Geological Sciences, Beijing
Aaron Cavosie
Curtin University, Bentley, WA

Abstract

Sediment-derived melts and the detrital products derived therefrom have been present in the geologic record since the Hadean Eon. While they are often smaller in volume compared to other felsic melts from arc settings, understanding the mode and volume of sediment assimilation is crucial to grasp the interplay between Earth's surface and its depths. Recent research has shown that changes in sedimentary compositions over time are mirrored in the composition of sediment-derived melts. This makes detrital mineral proxies unreliable for estimating the volume of sediment-derived melts through time.

The clastic sedimentary record is also extremely diverse in its isotopic signatures and degree of maturity. This compositional diversity is reflected in sediment-derived melts that reflect specific isotopic features of various petrotectonic settings. Sediment-derived melts are present oceanic and continental arcs as well as continental collisions. Oceanic arcs record sediment-derived melts with elevated δ¹⁸O but depleted εHf, whereas continental collisions produce melts with elevated δ¹⁸O and enriched εHf. In contrast, long-lived continental arc systems yield dramatic swings in isotopic signatures during the oscillations of retreating and advancing arc phases. Ophiolites also host sediment-derived granites intruding peridotite that carry isotopic signatures akin to biogenic sediments implying subduction and melting of deep marine sediment.

Sediment melting mechanisms vary, and specific mineral proxies can distinguish between fluid-present melting and muscovite- and biotite-dehydration melting. Identifying these mechanisms helps understand the conditions and compositional diversity of sediment-derived melts. Sediment-derived melts record plate tectonic-driven mass transfer and connect evolving surface conditions with the deep Earth. Despite being relatively low in volume, these granitoids are essential for comprehending the long-term evolution of plate tectonics and the sedimentary systems that contribute to their formation.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-391787

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