Abstract
Quantitative description and prediction of vein hosted deposits using fractal statistics have been tested using data collected from the Curraghinalt gold deposit, Sperrin Mountains, County Tyrone, N. Ireland. Goldbearing quartz veins are hosted by Neo-Proterozoic Dalradian (Southern Highland Group) age psammites, pelitic schists and graphitic schists. Veins trend E to ESE and cross-cut regional structures. Vein thickness (z) distributions closely approximate a power-law distribution of the form N(⩾ z) = cz -D,with an exponent (D) of 0.76 over three orders of magnitude. Vein spacing data approximate a log normal distribution with a mean of 2.92m. Numerical analysis indicates that the veins are more clustered than expected from a random distribution. Regions of high percentage extension and high vein density define vein clusters. The vein clustering relationship may be combined with the power-law thickness distribution and used in a predictive manner. The data may be used to constrain the probability of intersecting veins of potentially mineable dimension.
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Alsop, G.I., Hutton, D.H.W. (1993a) Major southeast-directed Caledonian thrusting and folding in the Dalradian rocks of mid-Ulster:implications for Caledonian tectonics and mid-crustal shear zones. Geol. Mag. 130:233–244
Alsop, G.I., Hutton, D.H.W. (1993b) Caledonian extension in the north Irish Dalradian:implications for the timing and activation of gravity collapse. J. Geol. Soc. Lond. 150:33–36
Baecher, G.B. (1983) Statistical analysis of rock mass fracturing. Math. Geol. 15:329–347
Childs, C., Walsh, J.J., Watterson, J. (1990) A method for estimation of the density of fault displacements below the limits of seismic resolution in reservoir formations. In:North Sea oil and gas reservoirs. II. Norwegian Institute of Technology, Trandheim, Graham & Trotman, London, pp., 309–318
Clifford, J.A. (1986) A note on gold mineralisation in County Tyrone. In: Andrew, C.J., Crowe, R.W.A., Finlay, S., Pennell, W.M., Pyne, J.F. (eds.) Geology and genesis of mineral deposits in Ireland. I. Assoc. Econ. Geol., Dublin, pp., 8–45
Clifford, J.A., Meldrum, A.H., Parker, R.T.G., Earls, G. (1990) 1980–90:a decade of gold exploration in Northern Ireland and Scotland. Trans. Inst. Min. Metal. 99:B133–138
Clifford, J.A., Earls, G., Meldrum, A.H., Moore, N. (1992) Gold in the Sperrin Mountains, Northern Ireland:an exploration case history. In:Bowden, A.A., Earls, G., O'Connor, P.G., Pyne, J.F. (eds.) The Irish Minerals Industry 1980–1990. I. Assoc. Econ. Geol., Dublin, pp., 77–88
Cox, D.R., Lewis, P.A.W. (1966) The statistical analysis of series of events. Methuen, London
Earls, G., Clifford, J.A., Meldrum, A.H. (1989) Curraghinalt gold deposit, County Tyrone, Northern Ireland. Trans. Inst. Min. Metal. 98:B50–B51
Gillespie, P.A., Howard, C.B., Walsh, J.J., Watterson, J. (1993) Measurement and characterisation of spatial distributions of fractures. Tectonophysics 226:113–141
Hartley, J.J. (1938) The Dalradian Rocks of the Sperrin Mountains and Adjacent Areas in Northern Ireland. Proc. R.I. Acad. 448:141–171
Heffer, K.J., Bevan, T.G. (1990) Scaling relationships in natural fractures-data, theory and applications. Proc. European Petrol Conf. 2, pp. 367–376. Society of Petroleum Engineers, Reprint no. 20981, pp. 1–12
Huang, Q., Angelier, J. (1989) Fracture spacing and its relation to bed thickness. Geol. M. 126:353–362
Jackson, P., Sanderson, D.J. (1992) Scaling of fault displacements from the Badajoz-Cordoba shear zone, SW Spain, Tectonophysics 20:179–190
Johnston, J.D., McCaffrey, K.J.W., Loriga, M.A., Watterson, J., Walsh, J.J., Gillespie, P.A. (1994) A manual describing recording, analysis and prediction of vein and related fracture distributions. MIRO, Lichfield, UK, 222 pp
Laslett, G.M. (1982) Censoring and edge effects in areal and line transect sampling of rock joint traces. Math. Geol. 14:125–140
Marrett, R., Almendinger, R.W. (1991) Estimates of strain due to brittle faulting:sampling of fault populations. J. Struct. Geol. 13:735–738
Priest, S.D., Hudson, J.A. (1981) Estimation of discontinuity spacing and trace length using scanline surveys. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 18:183–197
Sanderson, D.J., Roberts, S., Gumiel, P. (1994) A fractal relationship between vein thickness and gold grade in drill core from La Codosera, Spain. Econ. Geol. 89:168–173
Scholz, C.H. (1990) The mechanics of earthquakes and faulting. Cambridge University Press, Cambridge, 439 pp
Walsh, J.J., Watterson, J., Yielding, G. (1991) The importance of small-scale faulting and their effects on fault-related regional extension. Nature 351:391–393
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Regrettably, Dave Johnston lost his life on 2nd October 1995 whilst carrying out fieldwork in western Ireland
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McCaffrey, K.J.W., Johnston, J.D. Fractal analysis of a mineralised vein deposit: Curraghinalt gold deposit, County Tyrone. Mineral. Deposita 31, 52–58 (1996). https://doi.org/10.1007/BF00225395
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DOI: https://doi.org/10.1007/BF00225395