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Pearce, Julian A; Rogers, Nick; Tindle, A J; Watson, J S (1986): Geochemistry and petrogenesis of basalts from DSDP Leg 92 holes [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.790794, Supplement to: Pearce, JA et al. (1986): Geochemistry and petrogenesis of basalts from Deep Sea Drilling Project Leg 92, eastern Pacific. In: Leinen, M; Rea DK; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 92, 435-457, https://doi.org/10.2973/dsdp.proc.92.126.1986

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Abstract:
Basalts recovered on DSDP Leg 92 include all the major basalt types so far recovered from the ocean crust of the eastern Pacific. Basalts from Holes 597, 597A, 597B, 597C, and 599B are tholeiites exhibiting all the mineralogical and geochemical characteristics of N-type mid-ocean ridge basalts (MORB). Fragments of ferrobasalts and alkali basalts were also obtained, however, from Holes 60IB and 602B, respectively. Hole 597C, which penetrated 91 m into basement and is the deepest hole so far drilled in fast-spreading crust, yielded basalts that can be divided into three major lithologic units. The lowest unit, Unit III, contains modal olivine and comprises basalts which, at about 8 to 10% MgO, are as basic as any sampled from fast-spreading crust. The middle unit, Unit II, is the most evolved; its basalts are olivine free and contain between 6 and 7.5% MgO. The upper unit, Unit I, is intermediate in composition between Units II and III; it is characterized by both modal olivine and glomerocrysts made up of plagioclase and rare olivine. Unit I is probably a massive flow, whereas Units II and III may be massive flows or sills. The basalts appear to have undergone three stages of alteration ("deuteric," "relatively reducing," and "oxidizing"), the intensity of alteration decreasing markedly downcore. Hole 597B, at 26.4 m of basement penetration the only other "deep" hole, contains just one lithologic unit, which closely resembles Unit I of Hole 597C.
Petrogenetic modeling reveals that the three lithologic units in Hole 597C are cogenetic and that they were derived from a depleted mantle source similar to the source of the tholeiites and ferrobasalts sampled in other holes; the alkali basalts are the only rocks derived from enriched mantle. Lavas of Unit III probably lay on the olivine-plagioclase cotectic, whereas the other lavas lay on an olivine-plagioclase-clinopyroxene peritectic. Some 60% of closed-system crystallization is needed to generate the most-evolved from the last-fractionated tholeiite, and a further 50% crystallization (80% overall) is needed to generate the ferrobasalts. Xenocrysts of calcic plagioclase and pseudomorphosed olivine in tholeiites from Hole 597B and Unit I of Hole 597C, and in the ferrobasalts from Hole 601B, provide evidence, however, that some magma mixing may have taken place.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: -18.919591 * Median Longitude: -125.466249 * South-bound Latitude: -19.451500 * West-bound Longitude: -129.770500 * North-bound Latitude: -18.806300 * East-bound Longitude: -116.868500
Date/Time Start: 1983-03-02T00:00:00 * Date/Time End: 1983-03-26T00:00:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
7 datasets

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Datasets listed in this publication series

  1. Pearce, JA; Rogers, N; Tindle, AJ et al. (1986): (Appendix B) Major-elements, trace-elements and CIPW norms for DSDP Leg 92 holes. https://doi.org/10.1594/PANGAEA.790790
  2. Pearce, JA; Rogers, N; Tindle, AJ et al. (1986): (Appendix D) Geochemistry of feldspars from DSDP Leg 92 holes. https://doi.org/10.1594/PANGAEA.790792
  3. Pearce, JA; Rogers, N; Tindle, AJ et al. (1986): (Appendix E) Geochemistry of oxides from DSDP Leg 92 holes. https://doi.org/10.1594/PANGAEA.790793
  4. Pearce, JA; Rogers, N; Tindle, AJ et al. (1986): (Appendix C) Geochemistry of pyroxenes from DSDP Leg 92 holes. https://doi.org/10.1594/PANGAEA.790791
  5. Pearce, JA; Rogers, N; Tindle, AJ et al. (1986): (Table 1) Geochemistry for selected samples of basalts from DSDP Leg 92 holes. https://doi.org/10.1594/PANGAEA.790786
  6. Pearce, JA; Rogers, N; Tindle, AJ et al. (1986): (Table 3) Geochemistry in four feldspar phenocrysts from DSDP Leg 92 holes. https://doi.org/10.1594/PANGAEA.790787
  7. Pearce, JA; Rogers, N; Tindle, AJ et al. (1986): (Table 4) Geochemistry on phases from DSDP Leg 92 holes basalts. https://doi.org/10.1594/PANGAEA.790788