Active and ongoing gold exploration and mining in ... - IAGS 2011

More documents

Recommendations

Info

28 Orogenic events relating to CLGB development generated several phases of deformation. The earliest deformation phases preserved (D1, D2) involved roughly synchronous N- to NNE- and S- to SWdirected thrusting at the southern and northeastern margins of the CLGB (Ward et al. 1989). Northwest-, N-, and NE-trending D3 strike-slip shear zones, including the KiSZ hosting the Suurikuusikko deposit, cut early folding and thrusting, but may also reflect reactivation of older structures. Post-D3 events are limited to brittle, low-displacement faults. Representative structural data for the deposit are shown in Fig. 11. The Kiistala Shear Zone has a strike length of at least 25 kilometres (Fig. 8). The dip of this shear zone in the Suurikuusikko area is steeply east to sub-vertical (Figs. 11b and 11c). Known mineralisation occurs within N-trending and less frequently NE-trending (e.g., Ketola ore bodies, Fig. 9) shear zone segments. The KiSZ is a complex structure, recording several phases of movement. Most deformation has occurred by flattening accompanied by some strike-slip movement. Aeromagnet ic images of the KiSZ indicate early sinistral strikeslip movement along the zone. Immediately above the widest mineralised zones, late dextral strike-slip movements are recorded on shear planes bounding mineralised zones. It is not yet clear if the timing of mineralisation coincides with a combination of early and late shearing or only to the later dextral shearing event which now delineates the limits of gold mineralisation in most ore zones. An apparent correlation exists between points of more intense shearing within the KiSZ and the amount of gold present in host rocks (Fig. 12). The envelopes of ore bodies strike N and have a moderate N plunge. The control on the northerly plunge is not completely resolved: factors to be explored include the role of intersections between multiple shear planes, and of the intersections of depositional surfaces and shear planes. The orientation of regional fold axes (similar to axes in Fig. 11a) may also have a role in determining favourable sites for mineralisation during shearing. Sulphides and host rocks show some evidence for deformation relating to post-mineralisation movements on host shear planes. Post-mineralisation brittle faults crosscut mineralised zones but are not known to cause significant displacement of ore lenses. Fig. 11. These stereoplots show the orientations of deformation features observed for Suurikuusikko (ordered from oldest to youngest). Figure 11a, top left, shows bedding (dots), the trend of the typical regional foliation (lines) formed prior to movements of the KiSZ related to mineralisation, and fold axes measured in the deposit area (stars). Figures 11b (top right) and 11c (bottom left) show the orientation of the ‘graphitic’ shear zones (e.g., Figure 10) associated with the KFZ and ore zones. Figure 11d (bottom right), shows the common orientation of post-mineralisation faults, although NE- (e.g., Fig. 11a) and E-striking faults and veins are also seen. Plots are lower hemisphere projections on equal area nets; point symbols are poles to planes with frequency contours, stars in Figure 11a are plunging lines; lines are planes). Plots after Patison et al. (2006b) and Patison (2001).
Fig. 12. These figures show 3D solid geology models for the deposit completed in 2004 (Patison 2006b). In both figures the coloured solids are assay-based ore solids for gold grade (≥ 1 g/t Au). The brown solid is a solid of the host shear zone constructed to show zones were deformation intensity is highest. Figure on right (near plan view with slight N plunge) and figure above (vertical section) show the shear-bound nature of the ore zones. Sheared bedding contacts which are also mineralised (unmineable grades at the time of model creation) are illustrated by the moderately east-dipping solids. Truncation by cross faults is also evident in the plan view figure. 29
Page 1: FIELD EXCURSION Active and ongoing
Page 4 and 5: Eilu, P. & Nykänen, V. 2011. Activ
Page 6 and 7: Excursion program and route Introdu
Page 8 and 9: 8 Introduction Pär Weihed, Olof Ma
Page 10 and 11: 10 Svecofennian subduction-generate
Page 12 and 13: 12 Fig. 3. Stratigraphy of the Cent
Page 14 and 15: 14 Svecofennian orogeny. Mafic dyke
Page 16 and 17: 16 Deformation and metamorphism The
Page 18 and 19: 18 cal orogenic gold” below, foll
Page 20 and 21: 20 reported a Sm-Nd age of 2085±85
Page 22 and 23: 22 The least altered amphibole-chlo
Page 24 and 25: 24 Exploration The first indication
Page 26 and 27: 26 The mineralisation typically occ
Page 30 and 31: 30 Alteration in and around the dep
Page 32 and 33: 32 Hanhimaa gold project Matti Tali
Page 34 and 35: 34 Exploration Extensive regional g
Page 36 and 37: 36 Rompas Au-U prospect Michael Hud
Page 38 and 39: 38 Fig. 21. Low-altitude airborne m
Page 40 and 41: 40 Fig. 23. South Rompas region wit
Page 42 and 43: 42 References Agnico-Eagle 2007. Me
Page 44 and 45: 44 Kämäräinen, P. 2011. Kittilä
Page 46 and 47: 46 Rastas, P., Huhma, H., Hanski, E
Page 52: ISBN 978-952-9618-80-4 (Printed) IS

Active and ongoing gold exploration and mining in ... - IAGS 2011

Create successful ePaper yourself

Delete template?

Save as template?