Detailed petrographic descriptions including modal analyses on MS and FV samples are documented by Mackie (2000) and Gilmore (2000) in their University of Queensland honors theses, which are available in electronic form upon request. Here, we present and discuss mineral major element compositional data on MS, GS, and FV samples and whole-rock major element and selected trace element data on MS, BN, and FV samples.
Major and minor element compositions (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P, Cr, and Ni) of olivine, plagioclase, clinopyroxene, orthopyroxene, amphibole, and Fe-Ti oxides were analyzed on polished thin sections using a JEOL Superprobe JXA-8800L at The University of Queensland. Analytical conditions were optimized for standard silicates and oxides at 15-kV accelerating voltage with a 20-nA focused electron beam for all the elements, with the exception of Na and K, for which a broader beam (10 µm) was used. Routine analyses were obtained by counting for 30 s at peak and 5 s on background. Repeated analysis of natural and synthetic mineral standards yielded precisions better than 2% for all the major element oxides analyzed. For the minerals in Hole 735B samples analyzed, the precisions are better than 2% for SiO2, TiO2, Al2O3, FeO, MgO, and CaO; 5% for MnO, Na2O, Cr2O3, and NiO; and 10% for K2O and P2O5, depending on mineral types and elemental abundances. Instrumental drift was minimal over an analytical session of 2-3 days but corrected for when present by repeatedly analyzing standards as unknowns during the run. The analytical data are given in Tables T2 (olivine), T3 (plagioclase), T4 (clinopyroxene), T5 (orthopyroxene), T6 (Fe-Ti oxides), and T7 (amphiboles).
All MS, BN, and FV samples for whole-rock compositional analysis involved a thorough cleaning procedure. The pen marks, saw marks, sticker residues, and other suspicious surface contaminants were ground off all samples that were collected on board. The samples were then reduced to 1- to 2-cm size using a percussion mill with minimal power production. These centimeter-sized rock pieces were then ultrasonically cleaned in Mili-Q water, dried, and powdered in a thoroughly cleaned agate mill.
Major element oxides
(SiO2, TiO2, Al2O3, FeOt,
MnO, MgO, CaO, Na2O, K2O, and P2O5)
for MS and BN samples were analyzed using a Varian Liberty 200 inductively
coupled plasma-atomic emission spectrometer (ICP-AES) at Queensland University
of Technology, following the procedure of Kwiecien (1990). Precision (1 )
for most elements based on U.S. Geological Survey (USGS) standards (BCR-1,
BIR-1, AGV-1, and G2) is better than 1% with the exception of TiO2
(~1.5%) and P2O5 (~2.0%). Loss on ignition (LOI) was
determined by placing 1 g of sample in a furnace at 1000°C for several hours,
cooling in desiccator, and reweighing. These same major element oxides were
analyzed for FV samples using a Perkin Elmer Optima 3300 DV inductively coupled
plasma-optical emission spectrometer (ICP-OES) at The University of Queensland
with the analytical precisions similar to the above. No LOI was determined for
the FV samples because of small sample size. The analytical data along with
calculated CIPW norms are given in Table T8.
Minor and trace element
(Li, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, and Nb) abundances in these
same samples were analyzed on a Fisons PQ2+ inductively coupled
plasma-mass spectrometer (ICP-MS) at The University of Queensland with the
analytical conditions and procedures following Niu and Batiza (1997) and Eggins
et al. (1997) except for sample digestion, which was done using high pressure
bombs to ensure complete digestion/dissolution of ilmenite, zircon, and other
refractory phases in gabbroic rocks (vs. basalts). Precisions (1 )
are better than 1%-2% for Li, Ga, Sr, Y, Zr, and Nb and are better than 2%-4%
for Sc, V, Cr, Co, Ni, Cu, Zn, and Rb based on repeated analyses of highly
depleted basaltic samples like USGS reference rock standard BIR-1. The
analytical data are given in Table T8.