Does ophiolite obduction in the tropics drive global climate? A detrital sediment perspective

Earth´s last half-billion years exhibit alternating greenhouse and icehouse climates, but we do not know why.

Global climate reflects atmospheric CO2 partial pressure, a product of volcanic emission and silicate weathering drawdown, modulated by the biosphere. Global climate simulations on geological timescales show correlation with tectonic collisions.

However, collision simultaneously terminates arc volcanism and exposes fresh rock for weathering: these processes are hard to deconvolve.Recent studies have provocatively hypothesised that Earth’s climate state is set by ophiolite obduction in tropical collisions. Here, rapid weathering of reactive rocks efficiently consumes CO2.

This hypothesis yields a testable prediction: that the sedimentary archive of ancient tropical orogens will contain ophiolitic detrital minerals at the onset of icehouse periods.This study will determine ophiolite occurrence, type, and age in key sedimentary sections.

Automated heavy mineral analysis will identify ophiolite occurrences by the presence of detrital Cr-spinel, an ultrastable ophiolitic mineral. Trace element analysis will detect spinel sourced from mantle ophiolite.

Ophiolite emplacement age will be determined by novel in-situ Lu-Hf dating of apatite, which rarely crystallises at mantle conditions, but forms instead by metasomatic processes during obduction. Time-resolved paleo-geographic maps of ophiolite extent will be made available for paleo-climate models.