The Bruderheim meteorite

Abstract

Bruderheim, a detonating bolide, fell at 1:06 a.m., MST, on March 4, 1960. The fireball traveled on an azimuth of N 100°, at a slope of 40°, with an initial atmospheric velocity of 8 to 10 miles per second. More than 300 kilograms have been recovered from the fall area, a well‐defined ellipse centered about latitude 53°54′N, longitude 112°53′W. This ellipse is 312 miles long and 214 miles wide (5.6 by 3.6 km), with its long axis N80W and the larger individuals located near its southeast apex.

Compositional variations among whole‐rock fragments of the L6 chondrite Bruderheim

“…Our estimate of the proportion of feldspar in Bruderheim is very close to that of Baadsgaard et al (1961) and to the value for L-type chondrites reported by Mason (1965 Ebihara and Honda (1983), however. Such high proportions would raise the average et al (1961).…”

“…The composititons of the refined end-member phases are given in Table 4. ordinary chondrites, and Baadsgaard et al (1961) reported a very similar normative composition for Bruderheim, specifically. Based on those works and general considerations of traceelement distribution coefficients, we concluded that the elements we had determined (Na, Sc, Cr, Fe, Co, Ni, Se, La, Sm, Ebihara, 1982).…”

“…We thus chose the chemical compositions of these phases, excluding ilmenite, as the end-member components for our modelling. We omitted ilmenite because it is a minor phase «0.20 wt.%) in L-type chondrites generally and in Bruderheim specifically (Mason, 1965;Baadsgaard et al, 1961) and we obtained no Ti concentrations with which to constrain its abundance in our calculations.…”

“…We thus used a composition representing mixtures of olivine and orthopyroxene as a single component in the mixing calculations; we represent this mixing end member, as opposed to the actual mineral phases, by OL+OPX. We began with an OL+OPX composition corresponding to 62% olivine and 38% orthopyroxene (Baadsgaard et al, 1961). We used concentrations of trace elements other than REE from studies of other L6 chondrites by Curtis and Schmitt (1979) and Allen and Mason (1973).…”

Mineralogy, Petrography and Chemistry of the Chondrite, Kamiomi, Sashima‐gun, Ibaraki‐ken, Japan

“…Much of the plagioclase is probably present both as submicroscopically fine aggregates in the interstices between large grains of opaque minerals and other silicate phase, and as microcrystalline aggregates with fine-grained pyroxene between phenocrysts of olivine and orthopyroxene, especially in several chondrules. Such discrepancy of estimation of feldspar content between norm calculation and modal analysis is also observed in the Bruderheim chondrite (Duke et al, 1961;Baadsgaad et al, 1961).…”