Mauna Loa

1. OIB / Hawaiian Volcanism Francis, 2013 Mauna Loa

2. Hot-Spots producing Ocean Island Basalts (OIB)

3. Characteristic Features of OIB Lavas • Relative abundance of strongly olivine-phyric, picritic and/or ankaramitic, high-MgO lavas ("oceanites"). Clinopyroxene is the second phase to crystallize after olivine at approximately 8 wt.% MgO, while plagioclase does not appear as a liquidus phase in Hawaiian tholeiites until compositions with less than 7 wt.% MgO. • Primitive OIB lavas (high-MgO) are among the most Fe-rich picritic basalts on the Earth. • Primitive OIB lavas are also characterized by relatively low Al (Al2O3 15 wt.%) and Ca (CaO = 10 wt.%) contents compared to MORB. . • OIB lavas are enriched in all incompatible trace elements, including the high field strength elements (Nb, Ta, Zr, Hf), as well as the LIL (K, Rb, Ba) and LREE, compared to MORB. Typically, however, they exhibit a relative depletion in LIL elements (Ba, Rb, K) with respect to HFS (Nb) and LREE elements. • Unlike MORB, many OIB suites (although not all) exhibit an anti-correlation between trace element enrichment and isotopic enrichment

4. Koloa Koolau East Molokai Honolulu Lanai Mauna Kea Mauna Loa Kilauea Mauna Ulu Loihi ~ 8.5 cm/yr

5. Stages of Hawaiian Volcanism Post-Erosional:Honolulu Series, Kola Series Renewed volcanic activity following a hiatus on the order of 1 million years. Small cinder cones, explosive tuff rings or maar, and small valley-filling flows of highly undersaturated, primitive lavas. This stage has not started yet on the big island of Hawaii, but is present on Maui and older islands. Post Caldera:Mauna Kea, East Molokai At 12,000', thicker flows begin to accumulate in the caldera, eventually filling it and forming a thin cap on the shield. The beginning of this stage is marked by a transition from earlier tholeiitic series to later alkaline series lavas. Initially, these two types of flows are commonly interbedded, and transitional compositions are also erupted. The earliest alkaline lavas are usually relatively evolved hawaiites, but as alkaline magmas become dominant with time, they also become more primitive (AOB) and explosive, finishing with the development of a cinder cone field capping the shield. Shield building:Kilauea, Mauna Ulu, Mauna Loa, Lanai, Koolau The repeated eruption of highly fluid, extensive thin flows of tholeiitic basalt builds the main shield of the volcano, which usually has a well developed central caldera. There appears to be a progression from early picritic lavas to later olivine and quartz tholeiites (6-9 wt.% MgO) with height, as each shield builds to an elevation of 12,000 feet (4000 m) above sea level. Early Submarine: Loihi Early pillow lavas range from mildly alkaline basalts (AOB's) to tholeiites. There is a direct correlation between degree of vesicularity (and thus volatile content) and the degree of silica undersaturation.

6. Active Volcanoes Mauna Kea Post Caldera Kilauea Mauna Ulu Early Shield Mauna Loa Late Shield Loihi Early Submarine

7. Koolau Koloa East Molokai Honolulu Maui Lanai Mauna Kea Mauna Loa Kilauea Mauna Ulu Loihi

8. Deep Seated Plume?

9. Magmatic Suites Tholeitiic Suite: Kilauea, Mauna Ulu, Mauna Loa, Lanai, Koolau (Oahu) Oceanite (picrite)Ol-tholeiiteQtz-tholeiite The tholeiitic suite constitutes 98% of Hawaiian lavas. With the exception of one rhyodacite, all lavas of this magmatic suite are basalts, and there is a marked absence of intermediate and evolved lavas such as: andesite, dacite, and rhyolite. Olivine is the dominant phenocryt and individual tholeiitic suites commonly define tight olivine control lines, with the dominant rock type being Ql-tholeiite. The most magnesian reported olivine has a composition of Fo 91 (most Fo 88 or less). Olivine, however, is absent in the groundmass, presumably because of the olivine reaction relationship. The first cpx phenocrysts are augitic in composition (at MgO = 8.0 wt.%), but pigeonite and quartz are commonly found in the groundmass. Xenoliths: dunite and olivine-gabbro xenoliths are relatively rare.

10. Kilauea

11. Kilauea Iki

12. Mauna Loa

13. Mauna Loa

15. Hawaiian Tholeiites

17. Magmatic Suites Alkaline Suite: East-Molakai, Mauna Kea ankaramite AOBhawaiitemugearitebenmoreiitetrachyte (labradorite) (andesine) (oligocene) The alkaline suite comprises 2 % of Hawaiian lavas. Both olivine and clinopyroxene (MgO > 10 wt.%) are early phenocryst phases, and primitive lavas are ankaramitic. Unlike the tholeiitic suite, olivine commonly persists in the groundmass, along with titan-augite and interstitial K-spar instead of quartz. The alkaline suite exhibits a much broader range of Mg contents, which indicates more extensive crystal fractionation involving olivine, clinopyroxene, and plagioclase. The dominant lava type has a relatively evolved hawaiitic composition. Xenoliths: dunite, wherlite, gabbro; all relatively common.

19. Mauna Kea

20. Top of Mauna Kea

21. Post-Caldera Alkaline Suite Kilauea East Molokai

22. Stages of Hawaiian Volcanism Post-Erosional:Honolulu Series, Kola Series Renewed volcanic activity following a hiatus on the order of 1 million years. Small cinder cones, explosive tuff rings or maar, and small valley-filling flows of highly undersaturated, primitive lavas. This stage has not started yet on the big island of Hawaii, but is present on Maui and older islands. Post Caldera:Mauna Kea, East Molokai At 12,000', thicker flows begin to accumulate in the caldera, eventually filling it and forming a thin cap on the shield. The beginning of this stage is marked by a transition from earlier tholeiitic series to later alkaline series lavas. Initially, these two types of flows are commonly interbedded, and transitional compositions are also erupted. The earliest alkaline lavas are usually relatively evolved hawaiites, but as alkaline magmas become dominant with time, they also become more primitive (AOB) and explosive, finishing with the development of a cinder cone field capping the shield. Shield building:Kilauea, Mauna Ulu, Mauna Loa, Lanai, Koolau The repeated eruption of highly fluid, extensive thin flows of tholeiitic basalt builds the main shield of the volcano, which usually has a well developed central caldera. There appears to be a progression from early picritic lavas to later olivine and quartz tholeiites (6-9 wt.% MgO) with height, as each shield builds to an elevation of 12,000 feet (4000 m) above sea level. Early Submarine: Loihi Early pillow lavas range from mildly alkaline basalts (AOB's) to tholeiites. There is a direct correlation between degree of vesicularity (and thus volatile content) and the degree of silica undersaturation.

23. Magmatic Suites Post-Erosional Suite: Honolulu Series, Oahu, and Koloa Series, Kauai A.O.B basanite nephelinite mellilitite ( 5% norm Ne) (  5% norm Ne) ( 15% norm Ne) (  15% norm Me) (modal feldspathoid) (no modal plag) (modal mellilite) The post-erosional series comprises 0.1% of Hawaiian lavas. They are characteristically strongly silica undersaturated, and, although they exhibit a wide range of silica saturations, they are all relatively primitive with high Mg contents. They thus do not appear to have suffered significant low pressure crystal fractionation. Xenoliths: lherzolite, harzburgite, dunite, garnet pyroxenite, all relatively abundant.

24. Sodic Alkaline Mafic Volcanism

26. Eclogite divide

27. Eclogite divide

32. Fe / Mn Hawaii and other OIB suites have been shown to have higher Fe/Mn ratios than MORB The elevated Fe/Mn ratios of OIB magmas has also been claimed to reflect the incorporation of minor amounts of outer core material, which has a much higher Fe/Mn ratio than the mantle

34. Hawaiian tholeiites are enriched in all incompatible trace elements in comparison to MORB, and are characterized by distinctive convex-upwards fractionated REE patterns that peak at Pr. Regardless of the degree of enrichment in the LREE, Nb, and Ta, however, there typically remains a significant relative depletion in LIL elements such as K, Rb, and Ba. This appears to require the present of a residual hydrous phase, such as amphibole or phlogopite, in the mantle source regions of the some of the alkaline magmas. The foidites develop slight negative anomalies for HFSE elements, eg. Nb and Hf.

35. There is a systematic anti-correlation between degree of incompatible trace element enrichment and degree of Si saturation, and much of the trace element variation in the Hawaiian lavas can be explained in terms of mixing between two components. Going from tholeiite to AOB to basanite and then olivine nephelinite corresponds to a systematic increase in the degree of enrichment in LREE, Nb, and Ta, with little change or a slight decrease in the levels of HREE.

36. Recent Alkaline Basalts (8+ wt.% MgO) minor olivine frac. Hirschfeld dominant

38. Zr ppm

39. Lanai / Koolau End-Member

41. The lavas within many OIB suites define approximately linear arrays between two chemical and isotopic components, one relatively depleted and the other relatively enriched. Originally these were thought to correlate with the MORB source and primitive mantle respectively. However, it rapidly became apparent that these linear arrays were different in different OIB suites.

43. There are thus many "flavours" of OIB suites, and at least five different components are required to explain them. Furthermore, there are geographic correlations in the isotopic characteristics of OIB suites. For example, the DUPAL anomaly in the south Pacific is defined by the abundance of EM II OIB suites that appears to correlate with a lower mantle seismic tomography anomaly.

46. Inter-shield variations in Hawaiian tholeiitic picrites

47. The primitivetholeiitic lavas of the shield building stage of Hawaiian Islands range in compositions between two end-members: Tholeiitic End-Members Kilauea, Mauna Kea, Loihi Lanai, Koolau, Mauna Loa low Si, high Fe, Ti, Ca high Si, low Fe, Ti, Ca highest IE, Nb/Zr, Th/U lowest IE, Nb/Zr, Th/U low 87Sr/86Sr, high 143Nd/144Nd. high 87Sr/86Sr, low 143Nd/144Nd .7036 Nd = + 7 .7042 Nd = +1 low 18O  4.7 high 18O  6.0 high 206Pb/204Pb  18.6 low 206Pb/204Pb  17.9 low 187Os/188Os  0.13 ~ MORB high 187Os/188Os  0.145 Despite appearances, the Koolau source component is not equivalent to primitive mantle (low Rb/Sr, high 187Os/188Os, high, 18O), and the Kilauea source component is not equivalent to depleted mantle (DMM) (high 87Sr/86Sr, low 18O), nor Pacific ocean crust and/or lithosphere (high 206Pb/204Pb, low 187Os/188Os). Both of these source components would seem to be from the lower mantle.

48. Koolau Koloa East Molokai Honolulu Maui Lanai Mauna Kea Mauna Loa Kilauea Mauna Ulu Loihi

49. The Hawaiian Paradox The low Al and Ca of most primitive OIB picritic magmas, including those of Hawaii, are consistent with equilibration with a harzburgitic residue at pressures ranging from 1.5 to more than 3.0 GPa. If these OIB parental magmas were derived from the same Pyrolite mantle source that gives rise to MORB, then they would have to represent a greater degree of partial melting, beyond the point at which clinopyroxene disappears in the solid residue. This interpretation is supported by recent melting experiments on a Kilauean picrite (Eggins, 1992a), which is saturated only in olivine and orthopyroxene in this pressure range.

50. The Hawaiian Paradox The foregoing conclusion, however, is inconsistent with the fact that all Hawaiian primitive magmas are enriched in incompatible trace elements compared to MORB. To make matters worse, the buffered levels of heavy rare earth elements in magmas ranging from tholeiites through strongly alkaline basalts has convinced many trace element geochemists (Hofmann et al. 1984, Frey and Roden, 1987) that residual garnet must be present in their mantle source. Inversions of Hawaiian rare earth element data (Watson, 1993) also indicate melting in the presence of residual garnet. But olivine and garnet never coexist on the liquidus of primitive Hawaiian tholeiites.