M.J Mohammadzadeh; M Mahboubi Aghdam; P Mohebbi
Abstract
The Ghezildash massive sulphide copper deposit is located in the northwest of Iran. The area is a part of the ophiolotic colored mélange zone of NW Iran, also known as Khoy–Maku colored mélange. Copper mineralization occurred in part of basaltic meta-volcanic rocks, and extensive ...
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The Ghezildash massive sulphide copper deposit is located in the northwest of Iran. The area is a part of the ophiolotic colored mélange zone of NW Iran, also known as Khoy–Maku colored mélange. Copper mineralization occurred in part of basaltic meta-volcanic rocks, and extensive alteration zones such as chloritic–epidoitic along with minor carbonate and sericitic zones are consequently developed in the area. This paper aims at identifying hydrothermal alteration zones related to massive sulphide deposit particularly those associated with chloritic zones where the mineralization have been identified. Another aspect is to determine the elemental enrichment and depletion before and after alterations in the host rock. For this purpose, the alteration box plot was used, which approved Trend 4 of chlorite-carbonate zone in much of the samples and Trend 5 of sericite–carbonate in few samples. Furthermore, thin section studies showed similar results, confirming the method used. Maclean method as a useful reconnaissance tool for mineralized zones was then applied to identify the enriched and depleted alteration zones between unaltered host rock and altered chloritic and sericitic zones. Results of McLean method revealed in the chloritic alteration zone large enrichment of Fe and Mg and depletion of Na, K and Ca elements, which have occurred due to decomposition of feldspars in the rock during chloritic alteration. It was also observed that these rocks in the chloritic alteration zone were subjected to a moderate increase in Cu, Zn, Co, and V contents. Also, sericitic alteration zone showed a moderate enrichment in Fe and Mg. Therefore, alteration zone detection using box plot and mass change calculations by McLean method enabled us to identify mineralization zones in the Gezildash massive sulphide deposit of Khoy. Characteristic features of detected alterations and geochemical indices obtained by this study suggest the Cyprus type massive sulphide mineralization for the area associated with Cu-Zn enrichment and Ca and Na depletion. In some cases, very minor amount of K enrichment in sericitic zones was also observed. Overview of the deposit represents cluster form in a particular trend that emphasizes its structural control by faults. The presence of ophiolitic mafic volcanic rocks, Ocher horizons, exhalative cherts and regional pyrite horizons are considered as exploration signs for this deposit.
A Naseri; M.J Mohammadzadeh; P Mohebbi; P Javani
Abstract
Gharahchaman is located inthe Urumieh Dokhtar zone in east Azerbaijan. The area is mostly comprises of intermediate to acidic intrusive and extrusive, Oligocene igneous rocks along with younger sedimentary units. The regional geochemical exploration program with the aim of delineating potential zones ...
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Gharahchaman is located inthe Urumieh Dokhtar zone in east Azerbaijan. The area is mostly comprises of intermediate to acidic intrusive and extrusive, Oligocene igneous rocks along with younger sedimentary units. The regional geochemical exploration program with the aim of delineating potential zones in the area were attempted by collecting 394 stream sediment samples, which analyzed for 44 elements. Most of the exploration programs are routinely based on the positive anomalies (+ve) detection and the negative halos (-ve) are rarely considered. The depletion of some pathfinder elements may be related to ore mineralization in the area. Therefore (-ve) halos also can be significant in regional exploration. Conventionally, negative anomalous threshold values have been calculated in the same way as positive one, which causes drawbacks and hinder their application. In this paper an attempt were made to construct integrated models of (-ve) and (+ve) potential maps for detecting optimized geochemical pattern. It can be deduced from this study that the detected significant (-ve) halos, mostly are influenced by syngenetic processes and some are also related to ore bearing solutions. Detecting (-ve) halos of elements such as Sc, Sr, and Na in a particular pattern and in vicinity of (+ve) halos like Au, Cu, Pb, U, Zn are related to base metal mineralization and other important elements in the region. On the basis of combined distribution pattern of elements three models of geochemical anomalies are accompanied each other;1) Overlapping of multi-element (-ve) and (+ve) anomalies like (Rb, Sr); 2) Peripheral regional multi-element (-ve) anomalies that surround (+ve) anomalies like (-ve) halo of Sc around (+ve) halos of Ce, Rb/K and (–ve) halo of Sr with Ba/Sr ratio, felsic and chloritic zones in the area; 3) Discriminated Indices model of (-ve) and (+ve) halos of (Mo-Sr), (U-Sr), (Cu-Sr).This indicates that the combined study of (+ve) and (-ve) halos in regional geochemical exploration studies can be more significant in detecting hidden ore deposits. The distribution pattern of felsic and chloritic additive composite alteration zones match with Model2, which mutually correspond to (+ve) and (-ve) anomalies of Au and Sr respectively. Ultimately the results revealed deficiency in study of only positively concentration of elements along with faulted zones, whereas the present study emphasis that modeling corresponding of (-ve) and (+ve) halos along with results obtained from composite additive indices confirms NW-SE concentration of ore mineralization in the area.
