Hi Chris,
I'll check into the geology, but here are some references that may or may not help:
(Native metals in trap rocks of the Siberian platform. LA Russian A. V. Okrugin, B. V. Oleinikov, N. V. Zayakina & N. V. Leskova, Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva, 1101981, pp 186–204.
Electron microprobe and XRD data are given for native metals (Fe, Cu, Zn, Pb, Sn, Cd, and Al) in the trap rocks of the Siberian platform; nickelian Cu, alpha - and beta -bronze, stistaite, Mg2Si, and Al2CuMg are also reported. The separation of the native metal phases from the silicate matrix is considered to have occurred under mantle conditions during the interaction of the magma with intratelluric flux; the native phases started to crystallize at 1500o-1550oC and continued to 183oC. In the basic rocks, most of the native metals separated in the protomagmatic stage.
[84M/4093] Physicochemical conditions of formation of native metals and their stability in igneous magmas. I. A. Zotov, B. V. Oleynikov, A. V. Okrugin & YeE. B. Kurdyukov, Doklady, Academy of Sciences of the USSR, Earth Sciences Section, 2551980, pp 227–230.
Native Fe has been described repeatedly in granite, together with non-ferrous metals like Pb, Zn and Sn, as magnetic spherules whose shells consist of different Fe-bearing oxides. In traprock samples from the Siberian platform, many native metals were detected, such as Fe, Cu, Cd, Sn, Pb and Sb, their alloys, and even Al. Stability curves of metals and oxides relative to the log fO2 at different T are given, and three groups are discussed with regard to O and S affinity, protective coatings and reducing environments. For native Al in mafic rocks, the best explanation is the existence of a reducing mantle fluid capable of creating reducing conditions for mineral formation at different depths and transporting the metals there.
[85M/0773] Structurally ordered native aluminum in skarns. M. I. Novgorodova, N. A. Blokhina, A. I. Gorshkov & N. V. Trubkin, Doklady, Academy of Sciences of the USSR, Earth Sciences Section, 2561982, pp 109–111.
Native Al (M.A. 85M/0833) found in skarn-ore deposits, is associated with sylvite, muscovite, aragonite and native Cu, and is enriched in native Bi and Au. Al must have precipitated in a reducing gas flow, probably a mixture of hydrogen and hydrocarbons, from deep faults. The lattice parameter is 4.7 + or - 0.01 A, which is considerably more highly ordered than other synthetic and natural Al specimens with face-centred cubic cells.
[85M/0833] (Aluminium - a new mineral from a class of native elements. LA Russian B. V. Oleinikov & et al, Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva, 113(2), 1984, pp 210–215..
Grains of elongate, lamellar native aluminium are reported for silicified apomagnesian skarns in Tadzhik SSR; the grains are associated with xenomorphic grains of native gold, bismuth, graphite, moissanite, etc. The greyish white aluminium has a dull lustre and is anisotropic in reflected light; electron probe data indicate Al 99-100%. Two cubic varieties are recognized, with space groups Fm3m and Pm3m; indexed XRD powder data are tabulated for the former (a 4.04-4.07 A) which has strongest lines 2.35(10), 1.226(10), 2.03(9), 1.438(8) A. The formation of the native aluminium is ascribed to an ascending flow of reducing intratelluric fluids from depth. (M.A. 85M/0773)
[86M/3746] 'Hepoxides' of volcanic origin in the southern Sikhote Alin as indicators of processes at depth and of ore mineralization in extrusive rocks. L. G. Filimonova, Doklady, Academy of Sciences of the USSR, Earth Sciences Section, 2621982, pp 198–201 TJ tra.
Because native metal segregations are uncharacteristic of the Earth's lithosphere, the name 'hepoxide', meaning unoxidized, is proposed. It could be applied to all 'particles' containing native metals, as well as incompletely oxidized other components and silicates. 'Hepoxide'-forming processes may occur during magma generation and metamorphism as well as in supergene alteration zones. 'Hepoxides' in andesites and rhyolites of southern Sikhote Alin, NE Russia, are 0.5 mm in size and differ in composition. Globular magnetic samples contain magnetite, ilmenite and native Fe, Cu, Ni, Si, Al and Ca. The electromagnetic fraction consists mainly of Sn and Pb, plus admixed Zn, Cd, Fe, Cu, Ni, Sb, Bi and As. The diverse composition of these 'hepoxides' indicates the intermittency of magma-generating flows from the interior of the Earth.
[87M/6522] The origin of native aluminum. Ye. G. Osadchiy, V. I. Kupenko, Yu. V. Alekhin, N. S. Gorbachev & I. M. Romanenko, Doklady, Academy of Sciences of the USSR, Earth Sciences Section, 2671984, pp 182–184 TJ tra.
Native Al was detected in traprock from the Siberian platform, in a quartz vein in a gold deposit of the Urals, and in ores of the Nikitovka Hg deposits. The natural origin of such aluminium is confirmed, but the origin is not clear. Low-valence Al compounds, such as AlCl, AlF, and Al2O3 could be transported in the gas phase, and native Al could deposit as a result of disproportionation of such compounds while they are being transported at depth together with fairly dry reducing gases. The principal compositional feature of native Al is the constant presence of Cu, Zn and Si, plus lesser amounts of Mg, Fe, Ni, Ti, Mn and Ca. The occurrence of metallic Al in lunar soil may be explained by condensation of Al upon disproportionation of gaseous Al2O3 generated under conditions of explosive cratering.
[83M/0835] Petrologic significance of finds of native aluminum in mafic rocks. B. V. Oleynikov, A. V. Okrugin & N. V. Leskova, Doklady, Academy of Sciences of the USSR, Earth Sciences Section, 2431981, pp 122–124 TJ tra.
The discovery of native aluminium along with the native forms of Cu, Zn, Sn, Pb, Sb, Cd, and Fe indicates that a stage of metallization occurs in the evolution of magma of which nothing is known.
[96M/4552] Native aluminium in potash rhyolites of Dukat ore-field. L. G. Filimonova & N. V. Trubkin, Proceedings of the Russian Mineralogical Society, 125(2), 1996, pp 69–71.
Native aluminium has been discoverd among the authigenic mineral assemblages of the Dukat silver orefield; it is associated with fine-grained massive aggregates of goethite, halloysite, white mica, halite and graphite which fill the cavities in subvolcanic K-rhyolites. The peculiarities of this paragenesis and its localization allow the suggestion that the native aluminium could have been formed as a result of the decomposition of chlorides and hydrocarbons introduced into the limited space of gas cavities along with fluids of deep origin.
[02M/3294] Native aluminium in metasomatized sediments of the East Pacific Rise, 13°N. M. P. Davydov & P. A. Aleksandrov, Doklady, Russian Academy of Sciences, Earth Sciences Section, 379(5), 2001, pp 567–570 (Engli.
During cruise 3 of the Morskoi Geolog and cruise 2 of the Geolog Fersman in the late 1980s a large field of metalliferous sediments of more than 50 000 km2 in area was encountered in the northern subequatorial East Pacific Rise. The study of the light fraction of washed samples showed that the subsurface (0-5 cm) layer of these cores contains a mineral assemblage consisting of native aluminium (Al0) intergrown with Si-bearing aluminium hydroxides (alumogel) and alumogel particles free of visible metallic impurities. It was concluded that the aluminium and other metals were crystallized from a low-T mantle fluid that was rich in hydrocarbons, halides and sulphur.
