“…Silicon, Al, Fe, Ca, Mg, Na, K, Ti, Zr, Hf, P, Sr, As, Mn, S and Cl were determined by XRF (Baker 1982, van Zyl 1982, Hickson and Juras 1986, Rouseau and Bouchard 1986, Anderson 1987, King and Vivit 1988, Feret 1990, Gazulla et al 1991, Conture et al 1993, Buhrke et al 1998, Obenauf 2002). Silicon, Al, Fe, Ca, Mg, Na, K, Ti, Zr, Hf, P, Sr, As, Mn, S and Cl were determined by XRF (Baker 1982, van Zyl 1982, Hickson and Juras 1986, Rouseau and Bouchard 1986, Anderson 1987, King and Vivit 1988, Feret 1990, Gazulla et al 1991, Conture et al 1993, Buhrke et al 1998, Obenauf 2002).…”