serie NOVA TERRA nº 49

136 3. Geochemistry 3.1. Analytical methods Geochemical and isotopic analyses were performed on powdered rock samples milled at Universidad Complutense de Madrid and then analyzed for major and trace elements at Activation Laboratories Ltd. (ActLabs) in Canada. Procedural method for the analysis comprises fusion sample digestion (lithium metaborate or tetraborate) and ICP-OES or ICP-MS analytical techniques for major and trace elements, respectively. Resulting data from the geochemical analysis are given in Table 1 (major and trace elements) and Table 2 (REE; Rare Earth Elements). Additional whole-rock geochemical data obtained from M.F. Pereira et al. (2006) , who sampled equivalent layers, have been also incorporated to the geochemical plots and considered in the discussion. Sm – Nd isotope analyses ( Table 3 ) were performed at the Geochro- nology and Isotope Geochemistry Service of Universidad Complutense de Madrid ( https://www.ucm.es/isotope ) , using Isotope Dilution Mass Spectrometry (ID-TIMS). Samples were spikedwith appropriate amounts of a mixed 149 Sm – 150 Nd tracer before performing HF-HNO 3 -HCl sample digestion and a double-step chromatography separation process. Puri fi ed samples were loaded on a pre-conditioned Re triple- fi lament disposition and analyzed on an IsotopX-Phoenix mass spectrometer (TIMS), following a single collection and dynamic multicollection mode for Sm and Nd, respectively. All Nd isotope ratios were normal- ized to 146 Nd/ 144 Nd = 0.7219 ( O'Nions et al., 1979 ), and possible 142 Ce and 144 Sm interferences were corrected. La Jolla reference standard Table 1 Whole rock major and trace element composition of the Ediacaran metagreywackes of the Escoural Unit (basal allochthonous units of SW Iberia). EV-1 EV-2 EV-3 EV-4 EV-5 EV-6 EV-7 EV-8 EV-10 EV-11 EV-17 SiO 2 56.33 69.68 61.34 55.81 67.09 59.1 60.19 61.71 60.69 54.75 64.13 Al 2 O 3 18.18 14.92 18.19 19.28 16.18 18.31 18.23 15.8 17.64 18.6 16.82 Fe 2 O 3 8.39 3.8 5.91 7.99 4.12 7.37 7.13 4.29 5.22 8.61 5 MnO 0.098 0.052 0.075 0.106 0.1 0.103 0.079 0.097 0.038 0.103 0.045 MgO 4.14 1.16 3.09 3.8 1.84 3.65 3.59 3.07 3.57 4.97 2.4 CaO 1.39 0.5 0.37 1.05 0.78 0.65 0.5 1.82 0.79 1.47 1.06 Na 2 O 3 4.58 2.3 2.98 4.68 2.75 2.55 4.18 5.47 3.85 4.6 K 2 O 4.04 2.47 5.67 4.82 3.06 4.53 4.69 2.55 1.36 3.89 1.74 TiO 2 0.802 0.358 0.675 0.893 0.532 0.793 0.801 0.75 0.86 0.79 0.791 P 2 O 5 0.22 0.09 0.19 0.2 0.14 0.19 0.18 0.2 0.2 0.17 0.19 LOI a 2.35 2.01 2.34 2.53 1.59 2.72 2.41 4.33 4.17 2.29 3.22 Total 98.9 99.6 100.2 99.5 100.1 100.2 100.4 98.8 100.0 99.5 100.0 CIA 62 58 64 63 57 64 65 56 61 59 61 PIA 67 60 75 69 59 72 74 57 62 63 62 Sc 23 7 12 19 10 16 16 18 22 26 18 Be 3 3 5 5 3 4 5 2 2 3 2 V 178 35 84 150 56 129 124 179 208 179 132 Cr 120 30 60 100 50 90 80 110 130 130 100 Co 22 13 17 25 12 21 20 22 5 25 6 Ni 50 b 20 30 50 b 20 40 40 40 b 20 40 b 20 Cu 40 30 b 10 50 10 40 30 40 20 50 20 Zn 40 60 50 90 40 100 70 90 b 30 30 40 Ga 23 18 23 29 21 27 25 21 23 20 20 Rb 141 88 218 213 124 196 194 87 41 111 60 Sr 115 70 114 122 184 128 99 167 196 118 222 Y 26.9 34.9 37.1 39.9 38.9 31.9 33.7 28.9 31.1 28.0 25.1 Zr 185 241 221 190 268 170 174 169 197 189 198 Nb 11.9 13.9 19.5 18.7 17.0 19.1 19.8 11.1 11.8 9.4 10.9 Cs 4.7 2.1 5.1 5.9 2.6 5.5 5.5 2.8 1.8 4.2 2.3 Ba 784 689 1011 715 703 698 704 1798 769 973 743 Hf 4.1 5.8 5.6 4.9 6.6 5.1 4.8 4.5 5.2 4.5 5.5 Ta 0.9 1.3 1.6 1.3 1.4 1.4 1.4 0.8 0.9 0.7 0.8 Pb 8.0 11.0 7.0 10.0 7.0 10.0 7.0 b 5 b 5 7.0 b 5 Th 9.4 18.4 20.1 15.5 18.7 18.7 15.4 8.5 10.7 7.4 8.8 U 2.6 4.8 5.3 4.0 4.8 4.6 3.9 4.4 5.0 2.7 2.7 Al 2 O 3 /Na 2 O 6.1 3.3 7.9 6.5 3.5 6.7 7.1 3.8 3.2 4.8 3.7 Al 2 O 3 /TiO 2 22.7 41.7 26.9 21.6 30.4 23.1 22.8 21.1 20.5 23.5 21.3 SiO 2 /Al 2 O 3 3.1 4.7 3.4 2.9 4.1 3.2 3.3 3.9 3.4 2.9 3.8 K 2 O/Na 2 O 1.3 0.5 2.5 1.6 0.7 1.6 1.8 0.6 0.2 1.0 0.4 Ba/Sr 6.8 9.8 8.9 5.9 3.8 5.5 7.1 10.8 3.9 8.2 3.3 Ti/Zr 26.0 8.9 18.3 28.2 11.9 28.0 27.6 26.6 26.2 25.1 23.9 La/Th 4.2 3.3 2.9 3.3 3.3 2.9 3.2 4.1 4.1 4.2 4.8 Th/Sc 0.4 2.6 1.7 0.8 1.9 1.2 1.0 0.5 0.5 0.3 0.5 Zr/Sc 8.0 34.4 18.4 10.0 26.8 10.6 10.9 9.4 9.0 7.3 11.0 Zr/Th 19.6 13.1 11.0 12.3 14.3 9.1 11.3 19.9 18.4 25.5 22.5 Zr/Hf 45.1 41.6 39.5 38.8 40.6 33.3 36.3 37.6 37.9 42.0 36.0 Cr/Th 12.7 1.6 3.0 6.5 2.7 4.8 5.2 13.0 12.1 17.5 11.4 Cr/Ni 2.4 2.0 2.0 2.3 2.0 2.8 3.3 Th/Cr 0.08 0.61 0.34 0.16 0.37 0.21 0.19 0.08 0.08 0.06 0.09 Th/Co 0.43 1.42 1.18 0.62 1.56 0.89 0.77 0.39 2.14 0.30 1.47 Oxides are in weight percent (wt%). Trace elements are in parts per million (ppm). CIA: Chemical Index of Alteration ( Nesbitt and Young, 1982 ). PIA: Plagioclase Index of Alteration ( Fedo et al., 1995 ). a Loss on ignition. 290 R.D. Fernández et al. / Lithos 268 – 271 (2017) 285 – 301