"Apatitites" - their origin and genetic relation to the Fe-oxide-apatite ores of the Bafq District, Iran. A key feature to the understanding of the genesis of the Kiruna-type Ores
Zusammenfassung der Projektergebnisse
The investigated iron oxide-apatite (IOA) deposits from the southern sector of the Bafq District in central Iran and the associated apatitites are part of a sulfur-deficient, structurally controlled mineralization, formed during an Early Cambrian high-level magmatic event (≈530 Ma). They are associated with regional, pre-ore alkali metasomatism as evidenced by albite and K-feldspar formation. IOA deposits formed by a subsequent, deposit-scale alteration that led to diopside–actinolite (± andradite)–apatite-REE formation and locally created “apatitites”, whereas evolved iron-rich fluids formed the iron oxide–apatite-REE ores. Both apatite-bearing rocks are part of a regional-scale hydrothermal alteration system that – as evidenced by our apatite ages – was generated during the late phase of the ≈530 Ma, Early Cambrian highlevel magmatic and metasomatic events. This magmatic phase has produced a bimodal association of host rhyolitic tuffs and mafic rocks including sporadic SiO2-undersaturated rocks and minor barren andesites. Due to multistage metasomatism, which turned out to be more severe than anticipated by us, the major and trace element composition of the host rhyolites could not be used with confidence in order to elucidate the geotectonic setting of their formation and, hence, the environment in which the ore was formed. Instead we have utilized the mafic rocks which appear to have preserved their original chemical composition. The mafic volcanic rocks have trace-element signatures ranging from within-plate (alkaline lavas from Narigan) to destructive plate margin (at Zarigan and Sechahun), both of which occur at Lakkeh Siah and Gasestan. The most likely geotectonic setting where such diverse mafic volcanic rocks can be expected to occur in close spatial and temporal proximity is at an active continental margin – the southern sector of the Kashmar–Kerman tectonic zone – during a phase of back arc-extension, such as proposed for the Tertiary Candelaria deposit in Chile. Initial Nd isotopic compositions reveal that all rocks, including rhyolites and albitites, contain a major mantle-derived component which may have been present in their unmodified composition or introduced by the pervasive metasomatism.
Projektbezogene Publikationen (Auswahl)
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2007. Multistage metasomatism and mineralization at hydrothermal Fe oxide–REE-apatite deposits and “apatitites” of the Bafq District, Central-East Iran. In: Andrews, C. J. (Ed.), Digging Deeper 2. Cambridge Mineral Resources plc, Navan, Ireland, pp. 1501–1504
Daliran, F., Stosch, H.-G. & Williams, P.
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(2009). A Review of the Early Cambrian Magmatic and Metasomatic Events and their Bearing on the Genesis of the Fe Oxide-REE-Apatite Deposits (IOA) of the Bafq District, Iran. In: Williams P (Ed.): Smart Science for Exploration and Mining. Proc 10th SGA Biennial, Townsville 2009: 623–625
Daliran, F., Stosch, H.-G. & Williams, P.
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2010. Early Cambrian iron oxide–apatite-REE (U) deposits of the Bafq District, east-central Iran. In: Corriveau, L. & Mumin, H. (Eds.), Exploring for Iron Oxide Copper–Gold Deposits: Canada and Global Analogues (Short Course Notes 20). Geological Society of Canada, St. John’s, pp. 147–159
Daliran, F., Stosch, H.-G., Williams, P. J., Jamali, H. & Dorri, M.-B.
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2011. Uranium–lead ages of apatite from iron oxide ores of the Bafq district, east-central Iran. Mineralium Deposita 46, 9–21
Stosch, H.-G., Romer, R. L., Daliran, F. & Rhede, D.
