Graphitization of Organic Material in a Progressively Metamorphosed Precambrian Iron Formation

Science  13 Nov 1964:
Vol. 146, Issue 3646, pp. 917-918
DOI: 10.1126/science.146.3646.917


Organic matter in the sedimentary Biwabik iron formation in northern Minnesota shows a progressive increase in crystallinity where the formation is metamorphosed by the intrusive Duluth gabbro complex. X-ray diffraction of acid-insoluble residues shows that there is a complete range in crystallinity, from amorphous material in the unmetamorphosed sediments to completely crystalline graphite adjacent to the gabbro.