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GEOCHEMISTRY

Bulk Chemistry

The Granada specimen is an ultramafic material composed of 26.15% SiO2 (Table 2a). This value is considerably below the normative classification for a ultramafic basalt. Furthermore, the material is highly calcic, being composed of 39.36% CaO. The third most abundant oxide is FeO*, reported as both FeO and Fe2O3, at 18.32%. Other prominent oxides include MgO and MnO, which compose of 5.63% and 5.38% of the Granada material. Water occurs in both the H2O- and H2O+ states, having values of 1.52% and 3.13%, respectively. Analysis of the sample, yielded a 1.42 loss on ignition (LOI), corresponding to a positive gain on ignition.

Trace Element Geoschemistry

The Granada material shows a general enrichment in its REE pattern, relative to chondrite abundances (fig. 6). This enrichment is prominent, being from light rare earth elements (LREE) to heavy rare earth elements (HREE), as suggested by the chondrite- normalized pattern (CN). Moreover, REE's are not as abundant as LREE (values <10 x CN). Only one REE anomaly exists within the Granada material, being a small negative europium anomaly. An unusual depletion of chacophile and lithophile elements was found within the Granada material, with elements such as: zinc, silver, lead, bismuth, palladium, platinum, and gold being below detection limits (Table 2b). However, low trace amounts of tin and antimony are present. Despite the low distribution of chalcophile elements, a significant amount of copper (113 ppm) was found within the material. The greatest elemental concentrations are that of refractory elements such as barium and vanadium. Other elements such as carbon, chlorine, and sulfur have a high enough concentration to be reported as weight percents.

 




Table 2. (a) Bulk composition and (b) trace element composition of the Granada material. For (b) all values are in ppm unless indicated, and negative values indicate below detection limits.


Figure 6. REE chondrite-normalized pattern of the Granada material.

Oxygen Isotopes

Oxygen isotope analyses were conducted on both pristine samples and samples treated in oxalic and hydrochloric acid. Samples were treated in acid to remove potential secondary minerals and oxidation. A significant difference exists between the two analyses, such that samples that are pristine show a relative depletion in both 18O and 17O, in reference to the standard mean of ocean water (SMOW). The values are considerably high, with 18O being twice as abundant as 17O, suggesting significant fractionation from the parent material. The 18O and 17O values display a 1:2 ratio, consistent with differentiated planetary material. Moreover, little deviation exists in 17O from the terrestrial fractionation line. The overall average of the analysis is 14.10 for 18O and 7.20 for 17O, with D17O at -0.06.