Tf. Yui et al., EVIDENCE FOR SUBMARINE WEATHERING FROM METAMORPHOSED WEATHERING PROFILES ON BASALTIC ROCKS, TANANAO METAMORPHIC COMPLEX, TAIWAN, Chemical geology, 118(1-4), 1994, pp. 185-202
The metamorphosed paleo-weathering horizon(s) developed on basaltic ro
cks in the Tananao Metamorphic Complex forms distinct Al-Fe-rich rocks
and occurs as two parallel belts, demonstrating its potential as a st
ratigraphic correlation unit in this structurally complicated metamorp
hic terrain. These Al-Fe-rich rocks have been metamorphosed under amph
ibolite-/greenschist-facies conditions, leading to the formation of ga
rnet-chloritoid rocks/chloritoid-rich rocks. The chemical changes alon
g three profiles, from metabasite to garnet-chloritoid rock, show prom
inent K, Rb, Cs and Ba enrichment, yet, also, a large depletion of oth
er elements if it is assumed that Ti, Zr, Nb, Ta and Hf remained relat
ively immobile. The REE's, however, behaved non-coherently. These chem
ical characteristics are attributed to pre-metamorphic processes and a
re shown to be similar to those observed with submarine weathering of
basaltic rocks. In contrast, the chloritoid-rich rocks reveal distinct
K, Rb, Cs and Ba depletion. It is suggested that this resulted from s
ubaerial weathering processes. K enrichment is not an uncommon feature
in Paleozoic/Precambrian paleosols. The present case study demonstrat
es that submarine weathering should be considered as a probable cause.