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“LAG” A NEW CLASSIFICATION SYSTEM FOR CONCEALED MINERAL EXPLORATION | ||
| Iranian Journal of Science | ||
| مقاله 5، دوره 30، شماره 1، اردیبهشت 2006، صفحه 35-56 اصل مقاله (1.01 M) | ||
| نوع مقاله: Regular Paper | ||
| شناسه دیجیتال (DOI): 10.22099/ijsts.2006.2730 | ||
| نویسنده | ||
| S. ALIPOUR* | ||
| Department of Geology, University of Urmia, Urmia, I. R. of Iran | ||
| چکیده | ||
| Lag is a general term applied to coarse grained (> 2 mm), hard, but partially weathered rock fragments, which are concentrated at the surface through attrition of finer materials. Based on morphology, mineralogy and the origin of lag from the Cobar region of Australia, lag may be conveniently grouped into three broad morpho-mineralogical categories; (a) those with a rough, blocky, lithic morphology where fabrics of the parent rock are partially preserved and which evolved predominantly in erosional landforms, (b) a smoother pisoid lag, with a well-developed varnish or polished surface, which is most abundant in deeply weathered, erosional and depositional landforms, and (c) a detrital lag evolving in a range of situations and which is generally more abundant in Quaternary modern drainage landforms. Based on chemistry and magnetic character, two distinct types of magnetic and non-magnetic lag are readily recognised. The magnetic type may include both pisoid and occasionally lithic and ferrolithic pregnant with maghemite. Analysis for various trace elements indicates a drastic difference in their chemistry and anomaly detection ability. Magnetic lags contain anomalous Fe, Pb and other heavy metals, while lithics were enriched Cu, Zn and Mn. Spatially, magnetic lag have broader distribution compared to the lithic fraction, which is concentrated close to its original source. These unique characters of lag, revealing weak anomalies in covered surfaces and its abundance in relation to the erosional and depositional landforms, make them a preferred sampling media in geochemical exploration. The chemical data suggest that the magnetic lag fraction is more useful in reconnaissance exploration, and non-magnetics for follow-up work to locate mineralisation, which may justify partitioning a lag sample prior to analysis. | ||
| کلیدواژهها | ||
| Lag؛ lag classification؛ geochemical exploration؛ concealed deposits | ||
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