Genesis of iron-apatite ores in Posht-e-Badam Block (Central Iran) using REE geochemistry

Abstract

Rare earth elements in apatites of different ore types show characteristic patterns which are related to different modes of formation of the ores. Most of the apatite-bearing iron ores are associated with alkaline magmas with LREE/HREE fractionation varying from moderate to steep. Iron-apatite deposits in Posht-e-Badam Block (Central Iran) have a high concentration of REE (more than 1000 ppm up to 2.5%), and show a strong LREE/HREE ratio with a pronounced negative Eu anomaly. This REE pattern is typical of magmatic apatite and quiet distinct from sedimentary apatites (phosphorites) which have a low REE contents and Ce negative anomalies. On the other hand, they are comparable to the REE patterns of apatites in Kiruna-type iron ores in different parts of the world. The REE patterns of apatites, iron-apatite ores and iron ores are similar and only have different REE contents. This similarity indicates a genetic relation for these rocks. Most of the iron-apatite deposits in Central Iran have similar REE patterns too, which in turn show a genetic relation for all of these deposits. This similarity indicates a similar origin and processes in their genesis. There are some small intrusions around some of the iron-apatite deposits that are petrographically identified as syenite and gabbro. These intrusions also have REE patterns similar to that of iron-apatite ores. This demonstrates a genetic relation between these intrusions and iron-apatite ores. The REE patterns of apatites in different deposits of Posht-e-Badam Block iron-apatite ores show an affinity to alkaline to sub-alkaline magmas and rifting environment. The alkaline host rocks of Central Iran iron-apatite ores are clearly related to an extensional setting where rifting was important (SSE-NNW fault lines). A probable source for this large scale ore forming processes is relatively low partial melting of mantle rocks. The ores have originated by magmatic differentiation as a late phase in the volcanic cycle forming sub-surface injections or surface flows. These ores have formed during magmatism as immiscible liquids (silicate and Fe-P-rich magmatic liquids) which separated from strongly differentiated magmas aided by a large volatile and alkali element content. Separation of an iron oxide melt and the ensuing hydrothermal processes dominated by alkali metasomatism were both involved to different degrees in the formation of Posht-e-Badam Block iron-apatite deposits. We proposed that the separation of an iron oxide melt and the ensuing hydrothermal processes dominated by alkali metasomatism were both involved to different degrees in the formation of Posht-e-Badam Block iron-apatite deposits.

Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

“…Various studies of IOA deposits have proposed different petrogenetic models including magmatic (e.g., [58,66]), magmatic-hydrothermal [67], hydrothermal (-metasomatic) (e.g., [68][69][70]), and sedimentary exhalative (e.g., [71,72]). For the Bafq district, some researchers have referred to a magmatic model [17,28,73,74], whereas Torab and Lehmann (2007) [35], Jami (2005) [21], and Daliran (2010) [19] considered high-T hydrothermal fluids as being responsible for generation of some Bafq IOA deposits. Taghipour et al (2013) [75] argued that mixing of magmatic and non-magmatic fluids caused iron oxide mineralization and hydrothermal alteration in the Choghart deposit.…”

Genesis of the Meishan iron oxide–apatite deposit in the Ningwu Basin, eastern China: Constraints from apatite chemistry

“…The apatites from the Abagong deposit show significant negative Eu anomalies (Eu/Eu* = 0.17–0.41; Chai et al, ). The apatites from iron oxide‐apatite ores of Posht‐e‐Badam Block of Central Iran have a high concentration of REE (>1%) and show a strong LREE/HREE fractionation and negative Eu anomaly (Mokhtari et al, ). A similar pattern can be observed in the Meishan deposit (Figure ).…”

“…Chonddte‐normalized REE patterns for apatite in the Meishan and other Kiruna‐type deposits elsewhere in the world. Data for the Kiirunavaara deposit from Frietsch & Perdahl, ; the Esfordi from Mokhtari et al, ; and the Abagong from Chai et al, …”

“…The similarities between the REE patterns in apatite, magnetite, and the host volcanic and subvolcanic rocks suggest a genetic relation among them as shown in the Kiruna-type deposits by Frietsch and Perdahl (1995), in the Abagong apatite-rich magnetite deposit in the Chinese Altay orogenic belt by Chai et al (2014), and also in the iron-apatite ores in Posht-e-Badam Block of Central Iran by Mokhtari, Zadeh, and Emami (2013). In general, only a few studies on the REE patterns of apatites have been conducted for the Kiruna-type deposits (Chai et al, 2014;Frietsch & Perdahl, 1995;Jami, Dunlop, & Cohen, 2009; Mokhtari et al, 2013). The recent progress in microanalytical techniques (e.g., Laser ablation-inductively coupled plasma-mass spectrometry [LA-ICP-MS]) allows in situ geochemical analysis of apatite.…”

Structural, textural, geochemical and isotopic signatures of synglaciogenic Neoproterozoic banded iron formations (BIFs) at Bafq mining district (BMD), Central Iran: The possible Ediacaran missing link of BIFs in Tethyan metallogeny

“…These include immiscible magmatic-carbonatitic (Förster and Jafarzadeh, 1994;Samani, 1988;Daliran, 1990Daliran, , 2002Mokhtari et al, 2013;Taghipour et al, 2014), oxide magmatic melt (Jami et al, 2007) and hydrothermal IOCG and Kiruna (Jami, 2005;Daliran, 2002;Stosch et al, 2011;Bonyadi et al, 2011;Torab and Lehmann, 2007;Taghipour et al, 2013). These authors did not explore the role of galciogenic structures, textures and metal sources for a comprehensive genetic model of mineralization.…”