Weathering of Viamão granodiorite, south Brazil: Part 2 – Initial porosity of un-weathered rock controls porosity development in the critical zone

The development of porosity during rock weathering is a key process controlling nutrients release, water holding capacity available for plants and flow. Here we used X-ray Computed Tomography (XRCT) 14C PolyMethylMethAcrylate (PMMA) autoradiography to show how cracks are created enlarged initial stages (saprock saprolite) granodiorite in southern Brazil (Viamão - RS). physical evolution characterized by imaging the pore network, using 14C-PMMA XRCT methods. Combined with bulk measurements, they highlight increase degree (un-weathered ? = 1.66 %, saprolite 11.7 %). This related joint density D 0.28 mm?1, 0.94 mm?1) average opening microcracks w 2.4 µm, 3.9 µm) macrocracks 176 400 µm). However, these crack openings do not account variability that govern flows, here specific distribution ranging from submicrometre centimetre scale. results network un-weathered plays role or incipient weathering. aperture following subcritical cracking concept new pores formed chemo-mechanical processes. presence/absence fractures regolith certainly parameter different types (mafic vs felsic).