Petrogenesis of Ultramafic Xenoliths from the 1800 Kaupulehu Flow ...

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sTABLE 7 (Continued)SiO 3TiO 2AljO 3Cr 2 O 3FeO*MgOCaONa 3 OTotalSiM nA1 VITiCrMgFe 1 *CaNaTotalmgEnFsWo* TotalB451 290573-460955-6017-262O49049100-111-8820118O0320016O028094401720806O0354-03384-649-18-941-9Fe as FeO.66KAP35O880504-400395-9317-5819-3205699-561-871012900620014001109640182076100404-0348415O59-639-966KAP25O80O5
ULTRAMAFIC XENOLITHS FROM THE KAUPULEHU FLOW 181Fsdunitewehrllta& clinopyroxenite30Fio. 3. Clinopyroxene compositions for Hualalai lavas and Kaupulehu xenoliths plotted in theCaSiO 3 (wo)-MgSiO3(en)-FeSiO3(fs) triangle (mole percent). Clinopyroxene samples analyzed for trace elementsare labeled. Hualalai tholeiitic and alkalic basalt fields are from Bobrson & Clague (1988).TRACE ELEMENT AND ISOTOPIC COMPOSITIONSOF CLINOPYROXENESIsotopic analyses for Sr and Nd and the concentrations of K, Rb, Sr, Ba, and rare earthelements (REE), in the clinopyroxene separates from four dunite, two wehrlite, and twoolivine clinopyroxenite samples are given in Table 9 (see Appendices A and B for analyticalmethods). All the separates were acid leached after careful hand-picking to remove possiblesurface contaminants. The investigated samples were chosen to cover the entire range ofMg/Fe for clinopyroxene in the Hualalai xenoliths (Tables 6 and 7). Except for dunitesample X14, REE concentrations of clinopyroxene in the dunite xenoliths are higher thanthose in clinopyroxene from wehrlite and clinopyroxenite xenoliths (Table 9 and Fig. 5). Alleight REE patterns are convex upward (Fig. 5). Except for Sr, the concentrations of othertrace elements (K, Rb, Ba), are very low (Table 9). The clinopyroxene separates have143 Nd/ 14 *Nd ranging from 0-51293 to 0-51299 and 87 Sr/ 86 Sr ranging from 0-70348 to0-70367.EQUILIBRATION TEMPERATURESBecause of the very limited occurrence of orthopyroxene, geothermometry based on anassumption of coexisting pyroxenes must rely entirely on clinopyroxene compositions, andtherefore it yields only minimum temperatures. The method of Lindsley & Andersen (1983)gives values from 1000 to 1220 °C. On average, they are ~55°C higher than valuesdetermined by the method of Kretz (1982) and about 130°C higher than those calculated bythe procedure of Mysen (1976). One exceptional xenolith, dunite sample X2, has a relativelylow Lindsley-Anderson temperature of 915 °C. Sample 68KAP1, the only sample withcoexisting clinopyroxene and orthopyroxene, has a Lindsley-Andersen temperature of
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