Celestine discovered in Hawaiian basalts

Abstract We report here the first occurrence of celestine (SrSO4) in recent oceanic basalts. Celestine was found in moderately altered accidental volcanic blocks from Ka‘ula Island, a rejuvenated tuff cone in the northern Hawaiian Islands. This occurrence is novel not only for the presence of celestine but also for the absence of barite, the sulfate mineral most commonly found in oceanic hydrothermal deposits. Celestine was found lining vesicles and partially fillings voids within the matrix of several high Sr (2200–6400 ppm) Ka‘ula basalts. High-quality wavelength-dispersive microprobe analyses of celestine are reported here for near end-member celestine (>90%). The Ka‘ula celestine deposits are compositionally heterogeneous with large variations in Ba content (0.9–7.5 wt%) within single mineral aggregates. The most likely source of the Sr for celestine in the Ka‘ula basalts was the host basalt, which contains ~1200 ppm. This is about 10 times higher than normally found in mid-ocean ridge basalts and 4 times greater than commonly observed in Hawaiian basalts. Hydrothermal alteration by S-bearing fluids related to the eruption that transported these accidentally fragments probably mobilized Sr in the blocks. These S-rich solutions later precipitated celestine during or following the eruption. We were unable to confirm the origin for the Sr via Sr isotope measures because the Ka‘ula celestine was too fine grained, friable, and widely dispersed to be concentrated for Sr isotope analyses. Future studies of basalts from active volcanoes on oceanic islands, especially for basalts with elevated Sr contents (>1000 ppm), should be aware of the possible presence of celestine in moderately altered lavas.

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Nd and Sr isotope evidence linking mid-ocean-ridge basalts and abyssal peridotites

Nature ◽

10.1038/371057a0 ◽

1994 ◽

Vol 371 (6492) ◽

pp. 57-60 ◽

Cited By ~ 81

Author(s):

Jonathan E. Snow ◽

Stanley R. Hart ◽

Henry J. B. Dick

Keyword(s):

Sr Isotope ◽

Mid Ocean Ridge ◽

Isotope Evidence ◽

Ocean Ridge

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Evidence from ocean islands suggesting movement in the Earth

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1965.0029 ◽

1965 ◽

Vol 258 (1088) ◽

pp. 145-167 ◽

Cited By ~ 166

Keyword(s):

Upper Jurassic ◽

Oceanic Islands ◽

Chemical Characteristics ◽

Ocean Ridges ◽

East Pacific ◽

The Earth ◽

The Pacific ◽

Mid Ocean Ridge ◽

Volcanic Islands ◽

Ocean Ridge

Oceanic islands increase in age from the mid-ocean ridges towards continents and the andesite line reaching a maximum known age of Upper Jurassic. The Seychelles appear to be a continental fragment. Several pairs of lateral aseismic ridges extend from islands on the mid-ocean ridge to adjacent continents. Their continental junctions mark points on opposite coasts which would also fit if the continents were reassembled according to the criteria used by Wegener. As Holmes has shown each pair of ridges tends to have distinctive chemical characteristics. One possible explanation is that convection currents in the mantle rising along the mid-ocean ridges and sinking beneath trenches have carried the crust apart across the Atlantic, India and East Pacific Oceans. The lateral ridges may be approximately streamlines. Although Darwin showed that most volcanic islands sink, a few have been uplifted. Most of these lie a few hundred kilometres in front of deep trenches, suggesting that they may be on the crest of a standing wave in front of the trenches and that the crust is rigid. Of eleven straight chains of young islands in the Pacific ten get older away from the East Pacific Ridge. They could also be streamlines, fed by lava rising from deep within convection cells with stagnant cores. The regularity of ridges suggests non-turbulent flow.

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Mid-ocean-ridge rhyolite (MORR) eruptions on the East Pacific Rise lack the fizz to pop

Geology ◽

10.1130/g47820.1 ◽

2020 ◽

Vol 49 (4) ◽

pp. 377-381

Author(s):

Ryan A. Portner ◽

Brian M. Dreyer ◽

David A. Clague

Keyword(s):

East Pacific Rise ◽

Volcanic Rocks ◽

Lava Flows ◽

Bubble Coalescence ◽

Magma Ascent ◽

Fine Grained ◽

East Pacific ◽

Mid Ocean Ridge ◽

Volcanic Suite ◽

Ocean Ridge

Abstract Eruptions on the Alarcon Rise segment of the northern East Pacific Rise (23.55°N, 108.42°W) at 2500–2200 m below sea level (mbsl) produced the most compositionally diverse volcanic suite found along the submarine mid-ocean-ridge (MOR) system, offering an opportunity to compare mafic through silicic eruption styles at the same abyssal depth. Eruption styles that formed evolved volcanic rocks on the submarine MOR have not been studied in detail. The prevalence of lava flows along the MOR indicates that most eruptions are nonexplosive, but some volcaniclastic characteristics suggest that explosive styles also occur. Higher viscosities in intermediate (103–5 Pa·s) versus mafic (101 Pa·s) lavas on Alarcon Rise correspond with larger, more brecciated pillows, while highly viscous rhyolite lavas (106–7 Pa·s) formed rugged domes mostly composed of autoclastic breccia. Although high H2O contents (1.5–2.1 wt%), abundant volcaniclasts, and vesicularities up to 53% in rhyolite might imply eruption explosivity, limited fine-grained ash production and dispersal indicate an effusive origin. Higher viscosities of MOR rhyolite (MORR) magma and small eruption volumes, compared to MOR basalt (MORB), limit bubble coalescence and rapid magma ascent, two likely prerequisites for deep-marine eruption explosivity. This idea is supported by widespread dispersal of basaltic ash, but very limited production and dispersal of silicic ash on Alarcon Rise.

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Mantle heterogeneity beneath oceanic islands: some inferences from isotopes

Philosophical Transactions of the Royal Society of London Series A Physical and Engineering Sciences ◽

10.1098/rsta.1993.0007 ◽

1993 ◽

Vol 342 (1663) ◽

pp. 91-103 ◽

Cited By ~ 31

Keyword(s):

Alternative Hypothesis ◽

Melting Zone ◽

Oceanic Islands ◽

Alkali Basalts ◽

Mauna Loa ◽

Mid Ocean Ridge ◽

Mantle Sources ◽

Hawaiian Plume ◽

Mantle Helium ◽

Ocean Ridge

Radiogenic isotopes in oceanic basalts are extremely useful as tracers of long-lived heterogeneities in the Earth's mantle. Helium isotopes provide unique information in that high 3 He / 4 He ratios are indicative of relatively undegassed mantle reservoirs (i.e. mantle with high time-integrated 3 He/(Th + U) ratios). An alternative hypothesis is that high 3 He / 4 He ratios may have been produced by ancient melting events, if the solid/melt partition coefficient (K d ) for He is greater than that for Th and U (i.e. yielding relatively high He/(Th + U) in the residue of melting). However, the distribution of helium within basaltic phenocrysts, and olivine/glass helium partitioning within mid-ocean ridge basalts, suggest that helium behaves as an incompatible element during melting (K d (olivine/glass) < 0.0055), which strongly supports the hypothesis that high 3 He / 4 He ratios are derived from undegassed mantle reservoirs. Isotopic measurements of He, Sr, and Pb in Hawaiian volcanoes lavas demonstrate that the mantle sources have changed on extremely short timescales, between 100 and 10 000 years before present. The preferred explanation for these variations is that they represent heterogeneities within the Hawaiian mantle plume, combined with late stage melting in the lithosphere for post shield alkali basalts. Helium isotopic data from Kilauea, Hualalai and Mauna Loa suggest that the plume is presently located beneath Kilauea (and Loihi seamount), and constrain the melting zone of the Hawaiian plume to be less than 40 km in radius.

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