Evolution of Mauna Kea Volcano, Hawaii: Petrologic and geochemical constraints on postshield volcanism

Journal Article · Sat Feb 10 04:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB02p01271· OSTI ID:5010115

Frey, F A; Kennedy, A ^[1]; Wise, W S; Kwon, S T ^[2]; Garcia, M O; West, H ^[3]

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1. Massachusetts Inst. of Tech., Cambridge (United States)
2. Univ. of California, Santa Barbara (United States)
3. Univ. of Hawaii, Honolulu (United States)

The postshield stage of volcano construction formed as the magma supply rate from the mantle decreased. The basaltic substage (Hamakua Volcanics) contains a diverse array of lava types including picrites, ankaramites, alkalic and tholeiitic basalt, and high Fe-Ti basalt. In contrast, the hawaiite substage (Laupahoehoe Volcanics) contains only evolved alkalic lavas, hawaiite, and mugearite; basalts are absent. Sr and Nd isotopic ratios for lavas from the two substages are similar, but there is a distinct compositional gap between the substages. The authors conclude that the petrogenetic processes forming the postshield lavas at Maina Kea and other Hawaiian volcanoes reflect movement of the volcano away from the hotspot. Specifically, they postulate the following sequence of events for postshield volcanism at Mauna Kea: (1) As the magma supply rate from the mantle decreased, major changes in volcanic plumbing occurred. The shallow magma chamber present during shield construction cooled and crystallized, and the fractures enabling magma ascent to the magma chamber closed. (2) Therefore subsequent basaltic magma ascending from the mantle stagnated within the lower crust, or perhaps at the crust-mantle boundary. Eruptions of basaltic magma ceased. (3) Continued volcanism was inhibited until basaltic magma in the lower crust cooled sufficiently to create relatively low-density, residual hawaiitic melts. Minor assimilation of MORB-related wall rocks, reflected by a trend toward lower {sup 206}Pb/{sup 204}/Pb in evolved postshield lavas, may have occurred at this time. A compositional gap developed because magma ascent was not possible until a low-density hawaiitic melt could escape from a largely crystalline mush.

• OSTI ID: 5010115
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B2; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
580000* -- Geosciences
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DEVELOPED COUNTRIES
EARTH MANTLE
EVEN-EVEN NUCLEI
FEDERAL REGION IX
GEOCHEMISTRY
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