Oct 17, 1974 Fuego bomb/lapilli/ash samples for Terry Plank, Jan 2007
On Jan 23 I went through the 1974 ashes looking for samples that would follow Terry’s
request:
I read your Fuego paper on the plane and found it very useful in learning more about
these kinds of eruptions. I also looked at Roggensack's 2001 Geology paper. I think Kurt
did the basic first cut with melt inclusions from 1974, but your paper gave me another
idea for a neat study. The concern about clast size and melt inclusion viability
(devitrification, diffusion) is mostly lore. The 1974 eruption might provide an excellent
sample set with which to test this as a function of clast size. I wasn't sure what phi -3
corresponds to, but provided that there are large bombs/lapilli, it would be very useful to
study melt inclusions as a function of clast size, starting at the maximum (a few cm?) and
going down to a few mm. Ideally exploring the bomb-lapilli-ash transition (> 7cm, a few
cm, < cm). We might also learn about the possible diffusion of water out of melt
inclusions/phenocrysts in a way that could be useful to actually constraining cooling
rates or diffusivities.
So this would require a few samples - like 5-10, that range in fallout size (from bomb to
coarse ash) from the 1974 eruption. We would seek ol-hosted melt inclusions, and cpx, to
test the state of the melt inclusions and H in the cpx. Do samples like this exist?
I found the following samples, all with prefix VF 74-, which go from bombs to lapilli to
coarse ash:
Largest
128 scoria bombs from Los Pajales mostly 3-6 cm collected 19 Oct 7268 x16093 8 km N
134 bombs from Ojo de Agua collected 19 Oct 7197 x 16027 8.5 km WNW
137 scorious bombs 3-6cm, La Soledad collected 19 Oct 7277 x 16078 7 km N
Mid size lapilli
136 La Soledad scoria collected 19 Oct 7277 x 16078 7 km N
94 7233 x 15973 above Panimache 6 km SW fell 14 Oct, collected 17 Oct
91 7211 x 15953 Morelia 7 km SW fell 14 Oct, collected 17 Oct
92 7211 x 15953 Morelia 7 km SW fell 14 Oct, collected 17 Oct
129 7234 x 16064 cemetary, east of Quisache 7.5 km NW collected 19 Oct
Finer, about 1 mm
159 7220 x 16098 collected 23 Oct 11 km NW
160 collected 25 Oct 22 km SW at Sta Lucia
In the same box, I have sent a special sample of amphibole that was carried by a block
and ash flow into the valley of the Rio Taniluya in 2005 and collected by John Lyons.
This sample is labeled “Gu/F Amph 1”