Other
Scientific paper
Oct 1967
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1967gecoa..31.1871e&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 31, Issue 10, pp.1871-1872
Other
8
Scientific paper
Magnetic spherules have been discovered in the natural concentrates of ilmenite and other heavy minerals that occur in beach sands of both Pleistocene and recent age. The spherules range in size from 80 to 650 . Those in any given deposit match the grain size of the matrix sand. The spherules consist mainly of magnetite (FeFe 2 O 4 ), hematite ( -Fe 2 O 3 ) and wüstite (Fe 1- x O). No metal-bearing ones have been found to date. Electron-microscope analyses show that our samples contain three distinct chemical types of spherules: Type I is approximately 70% iron, 5% nickel, 0.3% cobalt and 0.2% chromium. Type II consists solely of 70% iron (oxygen is estimated at 30 %) or of 70 % iron plus 0.5 % manganese. Type III are iron-poor, glassy spherules that are rich in SiO 2 , Al 2 O 3 and minor elements. Type I spherules occur in a Pleistocene sand in Florida and in a recent one in Brazil. Although they are nonmetallic, they contain nickel and cobalt in meteoritic proportions and we believe they are of extraterrestrial origin. Type II spherules occur in both Pleistocene and recent sands, in the Greenland ice cap, and in samples from many other environments. Their origin remains unknown. Type III spherules were found only in a modern beach, where industrial contamination is likely and in a sample of sand processed in a dry mill. Spherules of this type may be either volcanic or industrial.
Einaudi Marco T.
Marvin Ursula B.
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