Document JNbaJ8Ln328gdEdb067kDpDvZ

PRODUCED BY FORD "For a long tine It van believed that the Italian 'amlantl' vere all the tremollte type becaoee the first exanlnatlona of the mate rial vere based on samples of tremollte. It vae only In recefit years that, after farther atudles, the prodvcera recognised that their products vere for th\ most pert chryaotlle vlth a long, flexible fiber." Tremollte asbestos has been mined In the Ratal, South Africa, vhere It occurs In green talcose rocks -- probably altered ultramaflc rocks similar to those of the Jamestown Series In the Barberton district of South Africa (Rail, 1918, p. 109). In the United States tremollte asbestos has been mined In small quantities near Powhatan and Pyleevllle, Maryland, vhere It occurs in nmpMbolired ultramaflc rocks. Anthophylllte asbestos also occurs In these eame rocks. Actlnollte. amoslte, and crocldollte asbestos Conmerclal mining of actlnollte asbestos Is practically unknown. No mining of amoslte asbestos occurs outside the Transvaal. In the past crocldollte vas mined In the Coehabamba, Bolivia, from rocks of Igneous origin. MAJOR OCCURRENCES OP CMRYSOTILE ASBESTOS The commercially most Important form of asbestos, chryaotlle, is found In three distinct types of deposits: (Type I) alplne-type ultramafic rocks, including ophiolltes, (Type 11) stratiform ultramaflc Intrusions, and (Type III) serpentlnlred limestones. Type I deposits are by far the most Important, furnishing at least 8S percent of the world's chryaotlle fiber. Type III deposits are relatively unimportant but do furnish some high quality fiber. Type I deposits a One example of a Type 1 deposit has already been discussed, the Fonkklla and Haljasolml fields of East Finland. In these deposits, how ever, the valuable asbestos mineral Is snthophylllte, not chryaotlle. The tvo most important asbestos producing localities In terms of production, past and present, are the serpentlnlred ultramaflc rocks of the central and southern Urals and of the Appalachian Mountains In 296 8005 0059 southeast Quebec and northern Vermont. The Russian and North American occurrences are similar; the serpentinltcs are of the alplne-type and part of ophlollte sequences (Coleman, 1977), The chryaotlle asbestos deposits of Quebec, and their extension Into northern Vermont, occur In altered Verldotltes, which form port of an ophlollte suite of rock types. Included In this suite. In addition to the perldotltcs (dunltes and hareburgites), are gabbro cumulates, diabase sille, tholelltlc pillow lavas, and red argillites. These units vere emplaced tectonically into the country rocks In early Ordo vician time. The perldotltea, regarded as fragments of oceanie crust and mantle, ere suggested to have undergone the following sequence of events: (1) the formation of perldotltes In an oceanic environment through lithosphere accretions and sea-floor spreading; (2) the fragmenta tion and tectonic emplacement; and (3) deformation of the ultramaflc rocks within the Cnmbro-Ordovician country rocks (Laurent and Rdbcrt, 1979). These same authors propose that eerpentlnicatlon occurred In tvo stages: (1) early eerpentlnicatlon In an oceanic environment at low temperatures, where llzardlte vas the principal serpentine mineral, and (2) late eerpentlnlzatlon In a dynamic regime nf tectonic transport and emplacement, where fracturing of the peridotlte masses took place. Chryaotlle asbestos formed In these late-atage fractures, probably In a tress environment. Chrysotlle-benrlng serpentinites font a part of a discontinuous belt of ultramaflc bodies and associated rocks extending for almost the entire length of the Appalachian Mountain chain. The major and active chryaotlle deposits are, however, centered In Quebec In the towns of Black Lake, East Broughton, Thetford Mines, and Asbestos; smaller active deposits are at Bale Verte, Newfoundland, and Eden Mills, north-central Vermont. Further south In the Appalachian Chain, the ultramaflc bodies generally contain only small amounts of chryaotlle; tints, only minor production of this fiber, vlth the exception of the Vermont Asbestos Croup operation at Eden Mills, has oceurred in the eastern United States. As already alluded to, these ultramaflc recks in Maryland, Virginia, North Carolina, and Georgia have been the sources of minor amounts of nthophyllltc and tremollte aobestoa. The Quebec chryaotlle deposits were first discovered In 1877 In the 297