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Application of geostatistical analyst methods in discovering concealed gold and pathfinder elements as geochemical anomalies related to ore mineralisation

Lindagato P., Li Y., Yang G., Duan F., Wang Z.

Geologos

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2018

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Vol. 24, No. 2

95--109

EN

The study area in the West Junggar Basin is known to be rich in hydrothermal gold deposits and occurrences, even though there has been minimum exploration in the area. It is here hypothesised that this area could host more gold deposits if mineral exploration methods were to be reinforced. This research is aimed at identifying geochemical anomalies of Au, and determining possible factors and conditions which facilitate the formation of anomalies by referring to As and Hg as gold pathfinders. Geostatistical analyst techniques have been applied to 9,852 stream sediments and bedrock data collected on a total surface of 1,280 km2 of West Junggar, Xinjiang (northwest China). The kriging interpolation and quantile-quantile plot methods, combined with statistical methods, successfully identified both Au and its pathfinders’ anomalies. In the present study, median was considered as background values (10.2 ppm for As, 9.13 ppb for Hg and 2.5 ppb for Au), whereas the 95th percentile were threshold values (28.03 ppm for As, 16.71 ppb for Hg and 8.2 ppb for Au) and values greater than thresholds are geochemical anomalies. Moreover, the high concentrations of these three discovered elements are caused primarily by hydrothermal ore mineralisation and are found to be controlled mainly by the Hatu and Sartohay faults of a northeast-southwesterly direction as well as their related secondary faults of variable orientation, which facilitate the easy flow of hydrothermal fluids towards the surface resulting in the formation of geochemical anomalies. Most of anomalies concentration of Au are found near the mining sites, which indicates that the formation of new Au anomalies is influenced by current or previous mining sites through geological or weathering processes. In addition, the low concentration of gold and its pathfinders found far from active gold mine or faults indicates that those anomalies are formed due to primary dispersion of hosting rock.

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Seismic and geochemical anomalies related to vertical migration of gas in the Radlin gas field

Pietsch K., Strzetelski W.

Geological Quarterly

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2001

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Vol. 45, No 1

1-14

EN

In the Radlin Rotliegend gas field (southwestern Polish Lowlands, Fore-Sudetic Region, Poznań Depression), modelling and reinterpretation of seismic data combined with surface gas surveys (free gas method) help identify "gas chimneys" and locate pathways of vertical migration. An almost impermeable Zechstein evaporite cover reduces the stream of vertical gas migration so that a dry surface geochemical zone occurs at the surface and no seismic disturbances are observed directly above the pay zone of the gas field. The surface gas anomalies form a halo-type pattern surrounding the gas field. The majority of surface hydrocarbon microseepages from the subsurface agrees with the seismically visualised geological structure. The belts of surface gas anomalies and the dry zones separating them run along the strike of Permian structures and faults. Vertical pathways of gas migration are recognisable as zones of seismic discontinuity and chaotic distribution of distinct reflections and diffracted waves. Seismic "gas chimney" effects coincide with surface hydrocarbon gas anomalies. Particularly, they appear above the upper terminations of faults disturbing the Zechstein deposits. The faults create the main a venues for secondary vertical migration of gas from the reservoir to the surface. "Gas chimneys" are observable in a shallow zone above the Muschelkalk (Tm) where higher gas saturation of more porous rocks produces a seismically traceable velocity effect.

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Analiza warunków występowania geochemicznych i geotermicznych anomalii w zapadlisku przedkarpackim

Litwin I.

Nafta-Gaz

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1999

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R. 55, nr 2

77--81

PL

Na podstawie analizy rozmieszczenia temperatur, pomierzonych na różnych głębokościach, wydzielono strefy geologiczne związane z heterogenną strukturą fundamentu przedgórza Karpat. W celu zbadania genezy geochemicznych i geofizycznych anomalii, nad złożem Bitków stworzono model tego złoża. Interpretacja modelu opiera się na fizykochemicznym przedstawieniu przekroju geologicznego badanego obiektu. Wykorzystanie wyników badań litologicznych, stratygraficznych i innych umożliwiło określenie charakteru mechanizmu przekazywania ciepła i masy.

EN

On the bases of analysis temperature distributions, measured at different depths, authors separate geological zones connected with heteregeneous structure of basement in Carpathian Foreland. To study origins of geochemical and geophysical anomalies above Bilków deposit there has been constructed a model of the reservoir. Interpretation of the model is based on physico-chemical representation of geological section of the target studied. Using the results of lithology, stratygraphy, and other examinations helped to determine nature of mechanisms governing heat and mass transfers.