Fig. 8. Representative chondrite-normalized (chondrite values, Sun and McDonough, 1989) trace element patterns for clinopyroxene in the Rio Boba mafic-ultramafic plutonic sequence. Fields of clinopyroxene in SSZ mantle clinopyroxenites and websterites of the Solomon Islands are from Berly et al. (2006). Clinopyroxene in gabbroic and Los Caños volcanic rocks from Puerto Plata ophiolitic complex and in metapicrites and high-Mg metabasalts of the Puerca Gorda Schists are from Escuder-Viruete et al. (2011c, 2014). See text for explanation.
The REE ratios in the clinopyroxene of the gabbronorites are also very fractionated [(La/Yb)C=0.06-0.28, average 0.14]. HREE ratios are 3-8 times chondrite value, showing convex-upward trace elements patterns with strongly fractionated LREE and flat HREE segments (Fig. 8f, h). These patterns exhibit prominent negative anomalies in Nb, Zr and Ti, and lack any Eu anomaly. Overall, clinopyroxene trace element patterns in the gabbronorites are subparallel to those of the pyroxenites but located at slight higher values. These trace elements patterns are subparallel and have REE ratios similar to those of the clinopyroxenes from the mafic-ultramafic boninitic cumulates, the Puerca Gorda metabasalts and the gabbroic rocks of the Puerto Plata SSZ ophiolitic complex.
The clinopyroxene from the troctolites also show trace elements patterns with very low HREE concentrations, 6-8 times the chondrite value, below N-MORB. These patterns are strongly fractionated [(La/Yb)C=0.10-0.12] with a slightly convex-upward shape and flat HREE segments (Fig. 8e). They are characterized by depletion of Zr and Hf relative to Th and LREE, and a Ti negative anomaly relative to HREE, but lack a Nb and Eu anomalies. As in gabronorites, the Th values are relatively high and the HREE ratios are 4-8 times higher than in the pyroxenites. These clinopyroxenes show trace elements patterns similar to those in mafic-ultramafic boninitic cumulates and layered troctolites of boninitic affinity of the Puerto Plata ophiolite complex.
The trace elements contents of clinopyroxene in metapicrites and high-Mg metabasalts of the Puerca Gorda Schists are displayed in Fig. 8g. The incompatible trace elements ratios are low and vary between 0.4 and 9.6 times the chondrite value, below N-MORB. The REE values are variably fractionated ([La/Yb]c=0.5-1.8; average 0.8). All trace element patterns are flat to slightly convex-upward and show depletion of Nb, Zr and Hf relative to Th and LREE, and Ti depletion relative to HREE. In general, crystal rims shows higher trace element values than the crystal cores. Crystal cores and rims lack a negative Eu anomaly, which could mean that the crystallization of clinopyroxene was not affected by plagioclase fractionation. These trace elements patterns are analogous to those of clinopyroxenes from the mafic-ultramafic boninitic cumulates and basalts of Los Caños Fm of the Puerto Plata ophiolite complex.