Data report: geochemistry and mineral chemistry of ultramafic rocks from the Kane area (MARK)

Abstract

A suite of serpentinized peridotites from Leg 153 was analyzed for major and trace elements. All the rocks are less-refractory peridotites. The mineral chemistry of olivines (Mg# = 90.3), orthopyroxenes (Mg# = 90.4), clinopyroxenes (Mg# = 91.6), and some Cr spinels (Mg# = 68.4; Cr# = 29.7) shows the characteristic features of minerals from less-depleted mantle peridotites. Some geothermometric calculations gave temperatures for the pyroxene system of about 1300°C, reflecting the prekinematic to synkinematic crystallization of the pyroxenes, and gave a range from 1180° to 1075°C for the mineral pair orthopyroxene and spinel. Oxygen-isotope determinations show δ 18 θ values of about 6%c for olivine, orthopyroxene, and clinopyroxene; δ 18 θ values from chromian spinel/magnetite vary between 2.9%e and 3.8%o, values from serpentine vary between 2.8‰ and 5.3%e, and whole-rock values vary between 2.9%e and 4.6‰. Two temperatures could be calculated from the oxygenisotope exchange for the mineral pair clinopyroxene and spinel: about 1100° and about 900°C. The 1100°C value nearly corresponds to the data obtained using the orthopyroxene-spinel mineral thermometer, and may indicate subsolidus deformation and recrystallization. The temperature range of the serpentinization could only be estimated. It depends upon the rock/water ratio, and may not have exceeded ~300°C. Finally, a calculation of possible rock/water ratios is given.

Tectonic structure, lithology, and hydrothermal signature of the Rainbow massif (Mid-Atlantic Ridge 36°14′N)

“…[] and Debret et al . []; abyssal serpentinites of ODP Leg 153 (23°21′N, MAR) from Burgath [] and Werner and Pilot []; abyssal serpentinites of ODP Leg 209 (15°20′N, MAR) from Paulick et al . []; hydrothermal sulfides from other MAR sites from Evrard [] and Fouquet et al .…”

Stable Isotopes in Seafloor Hydrothermal Systems: Vent fluids, hydrothermal deposits, hydrothermal alteration, and microbial processes

“…Serpentine mineral separates analyzed by Fruh-Green et al (1996) give a similar δ 18 O range from 3.2 to 5.4‰ and a tighter δD range from -51 to -69‰, consistent with a fairly uniform water rock interaction process. Similarly, Werner and Pilot (1997) found that whole rock δ 18 O ranges from 2.9 to 4.6‰ for serpentinites from the MARK area. (Fig.…”

Origin of Fe‐Ca‐Metasomatism in Exhumed Mantle Rocks at the MARK Area (23°N, ODP Leg 153) and Implications on the Formation of Ultramafic‐Hosted Seafloor Massive Sulfide Deposits

“…The spatial extent of mantle rocks affected by melt‐rock interaction is very restricted to the few millimeters at the contact with magmatic veins. Further away, mantle silicates have geochemical compositions comparable to the ones of serpentinized peridotites of Site 920 (Figure 6, Figure S2 in Supporting Information , Burgath et al., 1997; Cannat et al., 1997; Stephens, 1997; Werner & Pilot, 1997).…”

“…(1997), Cannat et al. (1997), Stephens (1997), and Werner and Pilot (1997). (a) FeO versus MgO content in wt.…”