serie NOVA TERRA nº 49

115 In this region, no samples were taken in the Upper Alcudian Unit, which unconformably lies on the Lower Alcudian turbidites, because the sedimentary environments correspond to transitional continental- fan-shallow marine deposits, which do not meet the purposes of the whole rock geochemistry of this paper, whereas the Pusa Shales are a better option to characterize the Upper Unit, but it does not crop out southwards of the Valdelacasa or Navalpino anticlines. 3.2. Analytical methods Geochemical and isotopic analyses were performed on powdered rock samples milled at Universidad Complutense de Madrid. Whole rock major and trace elements analyses were performed at Activation Laboratories Ltd (Actlabs) in Canada, using fusion with lithium metaborate or tetraborate for sample digestion. The analytical tech- niques for major and trace element determination were ICP-OES and ICP-MS, respectively. The results are given in Tables 1 to 4 . Sm – Nd isotopic analyses were performed at the Geochronology and Isotope Geochemistry Service of Universidad Complutense de Madrid, using Isotope Dilution Thermal Ionization Mass Spectrometry (ID- TIMS). Samples were spiked with a mixed 149 Sm – 150 Nd tracer and ana- lyzed in an IsotopX-Phoenix spectrometer (TIMS), in single collection and dynamic multicollection mode for Sm and Nd, respectively. The 143 Nd/ 144 Nd ratios were corrected for 142 Ce and 144 Sm interferences and normalized to 146 Nd/ 144 Nd = 07219 value ( O'Nions et al., 1979 ) in order to correct procedural and instrumental mass fractionation. Drifts from La Jolla reference value ( Lugmair et al., 1983 ) were corrected by analyzing the standard along with the samples, yielding an average value of 143 Nd/ 144 Nd = 0.511851 for 6 replicas, with an internal preci- sion of ±0.00002 (2 σ ). Errors on the 147 Sm/ 144 Nd and 143 Nd/ 144 Nd ra- tios were estimated at less than 0.1% and 0.006%, respectively. 3.3. Geochemical tools Metasedimentary rocks have been widely studied to unravel the composition of the upper continental crust ( Condie and Wronkiewicz, 1990; Taylor and McLennan, 1985 ). Some authors have developed use- ful discrimination diagrams to constrain the tectonic setting and the provenance sources using major element compositions ( Bhatia, 1983; Roser and Korsch, 1985, 1986, 1988 ), although major element diagrams should be used carefully ( Armstrong-Altrin and Verma, 2005 ). There is a general agreement about the relative absence of changes in the minor and trace element composition of sedimentary rocks after their deposition and during secondary processes; consequently Table 4 Whole rock rare earth element data of Pusa Shales (Early Cambrian). CIA-1 CIA-2 CIA-3 CIA-4 CIA-5 CIA-6 CIA-7 CIA-8 CIA-9 CIA-10 CIA-11 CIA-12 La 41.6 42.8 42.2 42.2 43.1 40.2 43.7 42.2 38.6 41.6 41.1 40.5 Ce 78 80.9 78.9 77.2 80.6 75 81.9 77.2 71.7 76.7 76.8 74.9 Pr 9.75 10.1 9.85 9.96 10.2 9.51 10.3 9.92 9.14 9.72 9.9 9.48 Nd 36.9 38.7 37.6 37.6 38.6 35.5 39.1 37.1 36.5 36.4 37.7 35.3 Sm 7.13 7.52 7.68 7.21 7.71 7.04 7.74 7.6 7.41 7.19 7.58 7.12 Eu 1.42 1.52 1.5 1.41 1.5 1.4 1.47 1.53 1.49 1.42 1.51 1.39 Gd 5.53 6.37 6.23 5.55 6.3 5.54 6.5 6.35 7.01 5.61 6.32 5.7 Tb 0.9 1.05 1.02 0.92 1 0.91 1.03 0.99 1.02 0.94 1.01 0.93 Dy 5.42 6.05 5.77 5.45 5.85 5.63 6.1 6.06 5.5 5.55 5.94 5.48 Ho 1.1 1.14 1.16 1.08 1.15 1.08 1.17 1.17 1.11 1.05 1.13 1.09 Er 3.04 3.28 3.23 3.15 3.31 3.01 3.4 3.32 3.11 3.08 3.21 3.02 Tm 0.464 0.493 0.5 0.484 0.503 0.456 0.506 0.517 0.466 0.476 0.511 0.469 Yb 3.15 3.31 3.32 3.2 3.29 3.14 3.25 3.3 2.93 3.04 3.36 3.2 Lu 0.455 0.456 0.484 0.466 0.492 0.459 0.487 0.491 0.445 0.454 0.471 0.455 Σ REE 195 204 199 196 204 189 207 198 186 193 197 189 Eu/Eu* 0.70 0.68 0.67 0.69 0.66 0.69 0.64 0.68 0.64 0.69 0.67 0.67 (La/Sm) N 3.60 3.51 3.39 3.61 3.45 3.52 3.48 3.43 3.21 3.57 3.35 3.51 (Gd/Yb) N 1.40 1.53 1.50 1.38 1.53 1.41 1.59 1.53 1.91 1.47 1.50 1.42 (La/Yb) N 8.83 8.65 8.50 8.82 8.76 8.56 8.99 8.55 8.81 9.15 8.18 8.46 Rare earth element data in parts per million (ppm). Table 3 Whole rock rare earth element data of Lower Alcudian greywackes (Late Ediacaran). CIA-13 CIA-14 CIA-15 CIA-16 CIA-17 CIA-18 CIA-19 CIA-20 CIA-21 CIA-22 CIA-23 CIA-24 La 30.3 33.1 27.6 27.3 29.1 27.4 29.9 30.7 33.4 39.5 35.2 33.4 Ce 60.4 65.5 55.4 54.3 58.6 55 60.7 60 66.3 78.7 70.1 65.5 Pr 7.6 8.06 6.86 6.62 7.26 6.75 7.49 7.53 8.34 9.92 8.76 8 Nd 29.1 31 26.2 26 28.4 26.6 28.8 29.4 32.1 38.1 33.6 29.6 Sm 5.61 6.04 5.32 5.42 5.42 5.28 5.84 5.94 6.84 8.09 6.91 5.77 Eu 1.25 1.38 1.19 1.18 1.26 1.14 1.25 1.26 1.41 1.44 1.23 1.23 Gd 4.73 5.22 4.67 4.52 4.4 4.22 4.5 4.93 5.84 6.73 5.66 4.24 Tb 0.76 0.89 0.75 0.72 0.77 0.75 0.8 0.78 0.99 1.18 0.9 0.7 Dy 4.43 5.39 4.6 4.64 4.57 4.38 4.75 4.58 6.01 7.01 5.35 4.1 Ho 0.91 1.05 0.9 0.92 0.91 0.87 0.92 0.92 1.19 1.38 1.08 0.8 Er 2.5 3.01 2.59 2.5 2.55 2.47 2.72 2.56 3.43 3.87 3.15 2.26 Tm 0.382 0.459 0.389 0.384 0.406 0.368 0.413 0.4 0.505 0.584 0.498 0.349 Yb 2.62 3.00 2.59 2.62 2.66 2.55 2.63 2.67 3.26 3.79 3.20 2.28 Lu 0.367 0.434 0.388 0.39 0.406 0.372 0.405 0.385 0.459 0.541 0.439 0.345 Σ REE 151 165 139 138 147 138 151 152 170 201 176 159 Eu/Eu* 0.75 0.76 0.73 0.73 0.79 0.74 0.75 0.72 0.69 0.60 0.60 0.76 (La/Sm) N 3.3 3.4 3.2 3.1 3.3 3.2 3.2 3.2 3.0 3.0 3.1 3.6 (Gd/Yb) N 1.44 1.39 1.44 1.38 1.32 1.32 1.36 1.47 1.43 1.42 1.41 1.48 (La/Yb) N 7.73 7.38 7.13 6.97 7.32 7.19 7.60 7.69 6.85 6.97 7.36 9.80 Rare earth element data in parts per million (ppm). 21 J.M. Fuenlabrada et al. / Tectonophysics 681 (2016) 15 – 30