serie NOVA TERRA nº 49

116 their geochemical features mostly depend on the nature of the source areas. Trace elements such as REE, Hf, Ti, Cr, Co, Zr, Nb, Ta, Y, Th and Sc make excellent discriminating proxies for provenance and tecton- ic setting determination studies ( Bhatia and Crook, 1986; McLennan et al., 1990; Taylor and McLennan, 1985 ), mainly because these ele- ments, and particularly their ratios (e.g. Th/Sc, La/Sc, Ti/Zr, Zr/Sc and La/Th) are preserved during sedimentary processes due to their low mobility during weathering processes, transport, diagene- sis or metamorphism ( McLennan et al., 1983; Nesbitt et al., 1980; Taylor and McLennan, 1985; Wronkiewicz and Condie, 1987 ), and their very low residence time in oceanic waters ( Henderson, 1982 and Holland, 1978 ). Similarly, incompatible and compatible elements and their mutual relationships allow distinguishing be- tween areas with more felsic or ma fi c source components. Elements such as La and Th; and the Co, Cr or Sc are commonly used to discrim- inate between felsic and ma fi c contributions in different tectonic en- vironments ( Feng and Kerrich, 1990; Taylor and McLennan, 1985; Wronkiewicz and Condie, 1987, 1990 ). The effects of homogeniza- tion in sedimentary processes result in a relatively uniform distribu- tion of REE in detrital rocks, that show the average composition of the source area, and whose pattern re fl ects the REE abundance in the upper crust, mainly because very limited or no REE fractionation takes place during deposition of fi ne-grained sediments ( McLennan et al., 1980; Taylor and McLennan, 1985 ). a b c Fig. 4. Chemical diagrams for the metasedimentary rocks from the southern Central Iberian Zone (Iberian Massif). (a) Chemical classi fi cation scheme for siliciclastic sediments ( Herron, 1988 ).(b)Th – Hf – Coternaryplot( TaylorandMcLennan,1985 ).CC,continentalcrust;OC,oceaniccrust.(c)Co/ThvsLa/Scplot(averagecompositionsofigneousrocksfrom Condie,1993 ). 22 J.M. Fuenlabrada et al. / Tectonophysics 681 (2016) 15 – 30