CERTIFIED ONTARIO REFERENCE MATERIALS PROGRAM AT THE GEOSCIENCE LABORATORIES, SUDBURY, ONTARIO, CANADA

The Ontario Geoscience Laboratories (hereafter referred to as the Geos cience Laboratories) have produced 30 in-house materials since 1970. T his experience, the limited availability of international rock standar ds in volume, and the recent acquisition of specialized equipment (cap able of homogenizing up to 1 t of sample), has led to the development of the Certified Ontario Reference Materials programme for the product ion of certified reference materials (CRMs). Given the geological dive rsity of Ontario, the decision was made to create two streams of refer ence materials. One is a suite of unaltered and altered volcanic rock reference materials that reflected the wide compositional range of Arc hean rocks of Ontario. Sample sites are clustered in the Abitibi Green stone Belt which includes the Timmins and Kirkland Lake mining camps. This region also hosts some of the world's largest and most prolific m ines of Au and Cu-Zn, smaller Ni deposits and one of the two internati onal type-localities of komatiite. Advantages of such a choice are ext ensive. The rocks in this area have been studied by the Ontario Geolog ical Survey (OGS) for 50 years and this expertise is readily available both in terms of appropriate chemistry and in sampling sites. Geologi cally, Archean volcanic rocks were typically extruded into a subaqueou s environment and cooled quickly. This facilitates a high degree of ho mogeneity. There are a wide variety of compositions available, clear a ssociation with mineral deposits and thus the reference materials may also provide excellent baseline material for environmental studies. In the 1970s, the OGS devised internationally used major element classif ication criteria which divided Archean volcanic rocks into three major clans that have several subtypes (komatiitic dan has ultramafic and b asaltic members; tholeiitic dan has Fe-, Mg-, basaltic, dacitic, andes itic, and rhyolitic members; and calc-alkalic dan has basaltic, andesi tic, dacitic and rhyolitic members). These rock types typically show d ifferent styles of alteration near ore deposits (i.e., chloritization, sericitization, carbonatization). The Archean volcanic rock suite wil l be comprised of these unaltered and altered rock types. The other gr oup will focus on materials that fill a specific geoanalytical need. B ased on the information above and the capacity of the Geoscience Labor atories geostandards programme (5 CRMs per year), it is anticipated th at several rock types will be prepared yearly. A calc-alkaline rhyolit e and an ultramafic komatiite have now been collected and other sites have been identified. Collection has commenced. After the sample is bo ttled, the homogeneity will be tested in our laboratories using valida ted methods. This will provide a tentative composition and will be fol lowed by round-robin determinations. The reference materials will be r eleased in 100 and 500 g plastic bottles to both the geoanalytical com munity and the exploration industry to monitor precision and accuracy in commercial surveys.