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Natland, James H (1982): Crystal morphologies and pyroxene compositions in boninites and tholeiitic basalts at DSDP Holes 60-458 and 60-459B [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.820205, Supplement to: Natland, JH (1982): Crystal morphologies and pyroxene compositions in boninites and tholeiitic basalts from Deep Sea Drilling Project Holes 458 and 459B in the Mariana fore-arc region. In: Hussong, DM; Uyeda, S; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 60, 681-707, https://doi.org/10.2973/dsdp.proc.60.137.1982

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Abstract:
Not all boninites are glassy lavas. Those of Hole 458 in the Mariana fore-arc region are submarine pillow lavas and more massive flows in which glass occurs only in quenched margins. Pillow and flow interiors have abundant Plagioclase spherulites, microlites, or even larger crystals but can be recognized as boninites by (1) occurrence of bronzite, (2) presence of augite-bronzite microphenocryst intergrowths, and (3) reversal of the usual basaltic groundmass crystallization sequence of plagioclase-augite to augite-plagioclase. The latter is accentuated by sharply contrasting augite and Plagioclase crystal morphologies near pillow margins, a consequence of rapid cooling rates. This crystallization sequence appears to be a consequence of boninites having higher SiO2 and Mg/Mg + Fe than basalts but lower CaO/Al2O3.
Microprobe data are used to illustrate the effects of rapid cooling on the compositions of pyroxene and microphenocrysts in a glassy boninite sample and to estimate temperatures of crystallization of coexisting bronzite and augite. A range from 1320°C to 1200°C is calculated with an average of 1250°C. This is higher by 120°-230° than the known range for western Pacific arc tholeiites and by over 300° than for calc-alkalic andesites.
Boninites of Hole 458 lack olivine and clinoenstatite but are otherwise chemically and petrographically similar to boninites that have these minerals. In order to distinguish the two types, the Hole 458 lavas are here termed boninites and the others are termed olivine boninites.
Arc tholeiite pillow lavas from Holes 458 and 459B are briefly described and their textures compared to fractionated, moderately iron-enriched, abyssal tholeiites. Massive tholeiite flows contain striking quartz-alkali feldspar micrographic intergrowths with coarsely spherulitic textures resulting from in situ magmatic differentiation. Such intergrowths are rare in massive abyssal tholeiites cored by DSDP and probably occur here because arc tholeiites have higher normative quartz at comparable degrees of iron enrichment - a result of higher oxygen fugacities and earlier separation of titanomagnetite - than abyssal tholeiites.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 17.863633 * Median Longitude: 147.056700 * South-bound Latitude: 17.862500 * West-bound Longitude: 146.934300 * North-bound Latitude: 17.864200 * East-bound Longitude: 147.301500
Date/Time Start: 1978-04-18T00:00:00 * Date/Time End: 1978-04-25T00:00:00
Event(s):
60-458 * Latitude: 17.864200 * Longitude: 146.934300 * Date/Time: 1978-04-18T00:00:00 * Elevation: -3447.0 m * Penetration: 465.5 m * Recovery: 97.6 m * Location: North Pacific/TRENCH * Campaign: Leg60 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 46 cores; 437 m cored; 28.5 m drilled; 22.3 % recovery
60-459B * Latitude: 17.862500 * Longitude: 147.301500 * Date/Time: 1978-04-25T00:00:00 * Elevation: -4121.0 m * Penetration: 691.5 m * Recovery: 176.2 m * Location: North Pacific/SEDIMENT POND * Campaign: Leg60 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 68 cores; 644 m cored; 28.5 m drilled; 27.4 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
3 datasets

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Datasets listed in this publication series

  1. Natland, JH (1982): (Table 3) Geochemistry of pyroxenes in boninite at DSDP Sample 60-458-28-1,142-146. https://doi.org/10.1594/PANGAEA.820202
  2. Natland, JH (1982): (Table 4) Geochemistry of glasses in boninite pillow fragments at DSDP Hole 60-458. https://doi.org/10.1594/PANGAEA.820203
  3. Natland, JH (1982): (Table 5) Geochemistry of glasses in pyroxenes and plagioclases at DSDP Sample 60-459B-66-3,3-4. https://doi.org/10.1594/PANGAEA.820204