Sean David

Some silica-rich eruptive products of the Twin Peaks Subfield, Black Rock Desert Volcanic Field, Utah

#Obsidian #rhyolite #volcanism #geology #geoscience #volcanicglass

Mahogany + snowflake obsidian

Twin Peaks Subfield, Black Rock Desert Volcanic Field, Utah

#Obsidian #rhyolite #volcanism #geology #geoscience #volcanicglass

Retrograde eclogite imprinted with blueschist facies minerals including phengite (golden flakey mineral), actinolite (black needles), and glaucophane (blue).

Franciscan Complex, California

#eclogite #blueschist #metamorphism #geology #geoscience #glaucophane #mica #amphibole

Oligocene rhyolite cut by andesite and pebble dikes. Extensive argillization and limonite staining. Initially identified as a quartz latite, the Packard Quartz Latite (35.27 ± 0.03 ma) plots as a subalkaline rhyolite.

East Tintic Mountains, Utah

#geology #geoscience #rhyolite #pebbledikes

Mineralogy folks, does this look like red beryl?

Matrix is rhyolite,
Topaz Mountain, Utah

Twinned topaz.
Thomas Mountains, Utah

#topaz #geology #geoscience #rhyolite #mineral #utah

Topaz
Sherry colored freshly collected crystals and one in matrix that has been exposed to the sun.
Thomas Mountains, Utah

#topaz #geology #geoscience #rhyolite #mineral #utah

So excited to be back here in a week!

Topaz
Thomas Mountains, Utah

#topaz #geology #geoscience #rhyolite #mineral

Spinel lherzolite mantle xenolith hosted by phonotephrite (collected with permission)

San Carlos Volcanic Field, San Carlos Apache Reservation, Arizona

#peridotite #xenolith #lherzolite #geology #geoscience #volcano

In things that make me happy, a bit of the collection...Lawsonite blueschist, eclogitic blueschist, glaucophanite, various eclogites, orthopyroxenite, clinopyroxenite, garnet websterite

#eclogite #pyroxenite #blueschist #clinopyroxenite #websterite #garnet #metamorphic #geology #geoscience

Olivine is my second fav mineral after pyropic garnet and am super loving this forsteritic olivine ring. Peridotite xenolith in phonotephrite is from the classic location of the San Carlos volcanic field.

#olivine #xenolith #peridotite

Abundany weathered olivine(?) Phenocrysts in a dike. Likely geochemically similar to Makapuʻu-stage dikes on the other side of Kailua and at Makapuʻu Kailua Member, Koʻolau Basalt, Koʻolau, Oʻahu

This looks like weathered olivine right? This olivine-phyric dike would be the only one I've encountered within the Koʻolau Caldera where hydrothermal alteration was extensive and unforgiving. It looks similar to Makapuʻu-stage (≤2.6 ma) picrites further south.

#geology #geoscience #picrite #dike

My hometown in the Koʻolau Caldera. Kailua Member of the Koʻolau Basalt and a dike of (likely) basaltic andesite. Reference location is super close to here. I recieved a grant that will cover next semester (that unfortunately has to be spent at a Utah university) but would rather be back here.

End of a hike over the subaerial Koko Rift from Hanauma to Kaupō. A sweatiest me standing on Kaupō flow (basanite) with Makapuʻu (tholeiitic picrites-basaltic andesite) rising behind. Olivine is the only phenocryst of Kaupō which have some of the highest MgO on the Koko Rift.

#geology #geoscience

Lots of Laumontite (zeolite) crystals precipitated in vesicles from circulating hydrothermal fluids in the Koʻolau Caldera (Kailua Member 9fnthe Koʻolau Basalt)

Widespread Laumontite precipitated in vesicles of the Kailua Member of the Koʻolau Basalt indicate circulating hydrothermal fluids here were around 300° C (Zeolite Facies).

Kailua, Koʻolau, Oʻahu

#geology #geoscience #zeolite #volcano #hydrothermal #amygdule #metamorphism

Plants called Vaccinium reticulatum outside of East Maui and Hawaiʻi Island are V. x pahalae. Vaccinium peleanum is a high elevation species typically with purple-blue fruit and glaucous leaves. Skottsberg lumped it into V. reticulatum but we don't follow Skottsberg's classifications in this home.

Muffins made with ʻŌhelo ʻai (Vaccinium reticulatum,V. peleanum), endemics of east Maui and Hawaiʻi Island and a close relative of the salmonberry (Rubus spectabilis) with the largest fruit in the genus, ʻĀkala (Rubus hawaiensis).

#botany #plantscience #rubus #vaccinium #plants #baking #hawaii

There is also a clinopyroxene xenocryst to the left of the xenolith. eruptions here were phreatomagmatic and thus highly explosive. Plant fossils preserved in the tuff are often so well preserved we can identify them down to the species.

Spinel peridotite mantle xenolith and accidental fragment of Koʻolau. Basalt (note the plag phenocrysts) hosted in melilite nephelinite tuff.

Moanalua vent, Honolulu Volcanics, Koʻolau, Oʻahu, Hawaiʻi

#geoscience #geology #volcanology #volcano #mantle #xenolith #spinel #peridotite #Hawaii

I do have a few pictures of Hawaiian garnet pyroxenite mantle xenoliths posted on here. They have a midlithospheric origin from an elevated geotherm and the cpx tends to be darker as they are often quite augitic.

Pyroxenites like eclogite are more fusile than peridotite and when melted the Si02 rich melt reacts with mantle peridotite forming secondary pyroxenite. That seems the most likely source of end-member Loa-trend (enriched loa) lavas like Makapuʻu Koʻolau, Lānaʻi, and Kahoʻolawe.

That would include in the Hawaiian plume a vertically stretched material of a possibly "pyroxenitic" (ancient recycled material ) of the Hawaiian Ultra-Low Velocity Zone at the core mantle boundary forming a filament.

The samples are from Germany, Turkey, and Norway and I put them there to show what possible source lithilogies for these super enriched melts could look like.

@callanbentley.bsky.social it won't let me edit after postingso I posted a comment to this post

Eclogite (Left) and garnet pyroxenite (sensu stricto. Right) on Makapuʻu-stage koʻolau basalt (likely basaltic andesite) at the type location of Makapu. Waimānalo is visible, all lavas except flow going into the ocean (Rejuvenation stage Kaupō flow, much younger and alkaline) are Makapuʻu-stage.

Makapuʻu-Stage #Koʻolau Basalt has the most radiogenic Sr87/86 of #Hawaiʻi #lavas, low εNd, Hf176/177, and Pb206/204, and high La/Nb and Sr/Nb indicating a filament of recycled material (secondary garnet #pyroxenite via #eclogite) of the Hawaiian ULVZ associated with the Pacific LLSVP.

#geology

Blowholes formed via caves eroded into expansive late shield-stage Koʻolau lavas ranging from picrites to basaltic andesite.

Makapuʻu-stage Koʻolau Basalt
Koʻolau, Oʻahu

#blowhole #ocean #hawaii #Basalt #geology

Peridotite mantle xenolith hosted by basanite
Nuʻuanu Pali vent (640-600 ka), Honolulu Volcanics, Koʻolau, Oʻahu, Hawaiʻi

Collection of @volcanoesinthesea.bsky.social

#peridotite #xenolith #geology #geoscience #volcano

Not a rock or mineral but a me training for #rugby pic....hopefully will translate into the ability to also carry so many mantle and crustal xenoliths.

One of several #basanite lava flows erupted from Kohelepelepe. Here it outcrops on #tuff emplaced via pyroclastic density currents.

Kohelepelepe, Koko Rift, Honolulu Volcanics, Koʻolau