REE geochemical characteristics of titanium-rich bauxites: the Permian Kanigorgeh horizon, NW Iran

Abstract

IntroductionBauxite deposits are formed by alteration and weathering of parent rocks rich in alumino-silicate minerals. These residual deposits are developed principally in tropical to subtropical climatic conditions with annual rainfall exceeding 1.2 m and an average temperature of >22 °C (Bardossy and Aleva, 1990;Mondillo et al., 2011). According to Bardossy and Combes (1999), these deposits are characterized into 3 major groups: lateritic bauxite deposits, karst bauxite deposits, and Tikhvin-type bauxite deposits. The first group is the product of in situ and direct chemical weathering of alumino-silicate rocks lying beneath the surface. The second group is developed on the surface of more or less karstified carbonates (limestone and dolomite) and scarce marls. The third group is formed on the surface of eroded alumino-silicate rocks and is the erosional product of lateritic bauxite deposits. Bardossy (1982), based upon parameters such as morphology and chemical compositions, classified the bauxite deposits into 6 distinct groups: Mediterranean type, Kazakhstan type, Timan type, Salento type, Tulsk type, and Ariege type. Based upon geographical situations, these deposits occurred in 7 belts throughout the world: the northern Mediterranean coast, Caribbean basin, Urals-Siberia-Central Asia, East Asia, Irano-Himalaya, Southwest Pacific, and North America.During the last few decades, geochemical investigations proved to have practical applications for determination of various aspects of formation and evolution of bauxite deposits such as the type of parent rocks; the roles of diagenetic, epigenetic, and supergene processes in connection to ore-forming mechanisms; physicochemical conditions of the environment of the ore formation (e.g., pH, Eh, intensity of draining, and climate); the mineral controls on distribution, mobilization, and fractionation of elements [particularly trace and rare earth elements (REEs)] in the course of bauxitization; and tectonometamorphic evolutions (Özlü,

Rare earth element geochemistry of the Upper Permian limestone: the Kanigorgeh mining district, NW Iran

“…Furthermore, the mentioned negative correlations furnish a strong reason for deposition of the limestone in a shallow marine environment. The chondrite-normalized REE patterns for (a) the bauxite ores (data from Abedini and Calagari, 2014) and (b) the limestone at Kanigorgeh.…”

“…The limestone is unconformably overlain by dolomites of the Elika Formation of Triassic age (Abedini and Calagari, 2014). The stratigraphic sequence in the area is followed by Cretaceous units (sandstone, shale, conglomerate, and limestone), and carbonate rocks of the Qom Formation (Miocene) and Quaternary alluvial sediments (Figure 1b).…”

“…The resulting melt was then cooled and dissolved in 100 mL of 4% nitric acid/2% hydrochloric acid. These solutions were then analyzed for major elements by using inductively coupled plasmaatomic emission spectrometry (ICP-AES) and for trace (Abedini and Calagari, 2014). and rare earth elements by inductively coupled plasmamass spectrometry (ICP-MS) methods in the laboratories of ALS Chemex, Canada (see Table 1).…”

“…By noting these explanations, in this study the distribution patterns of REEs along with Eu anomaly in the bauxitic ores and the host limestone were compared to determine the potential role of the latter in supplying REEs for the former. The distribution pattern of REEs normalized to chondrite (Taylor and McLennan, 1985) for the bauxitic ores (data from Abedini and Calagari, 2014) (Figure 12a) and the host limestone (Figure 12b) delineate totally different aspects. Comparison of these two patterns indicates that the differentiation degree of LREEs (La-Eu) from HREEs (Gd-Lu) in samples of the limestone is more pronounced than that of the bauxitic ores.…”

“…According to the structural divisions of Iran it is a part of the Khoy-Mahabad zone (Abedini and Calagari, 2014) (Figure 1a). The oldest lithologic units in the area are sandstone and shale of the Dorud Formation (Lower Permian) overlain by dolomite and limestone of the Ruteh Formation (Upper Permian).…”