Consistent patterns of rare earth element distribution in accessory minerals from rocks of mafic-ultramafic complexes

Abstract

This paper summarizes analytical data accumulated in the world literature and other materials about the regularities of the REE distribution in minerals contained in ultramafic and mafic rocks as accessory phases. These minerals are tentatively divided into two groups. The first includes garnets, zircons, apatites and perovskites, which can accumulate increased amounts of REE in their structure. The second consists of minerals whose structure can accumulate only limited contents of these trace elements. These are chrome-spinels, ilmenites, and micas. These minerals, in respect of REE geochemistry, are studied to a varying degree because of the different levels of accumulations of these elements, different degrees of occurrence in rocks, tiny sizes of their grains and other reasons. The analytical database formed on their basis includes about 600 original analyses. The overwhelming majority of presently available data on REE geochemistry in accessory minerals from ultramafic and mafic rocks have been published only in the recent 15 years. The studies became possible due to the development and introduction of new highly sensible microprobe analyses allowing detection of REE and many other trace elements in minerals grains directly in thin sections. The greatest numbers of these analyses were performed for garnets and zircons, fewer for apatites, and the fewest for chrome-spinels, ilmenites, micas, and perovskites. In general, the regularities of REE distribution in these minerals from ultramafic and mafic rocks are less studied compared to the rock-forming minerals from ultramafic and mafic rocks. Among the analytical methods, which were used to study the REE composition of accessory minerals, the most efficient was the mass-spectrometry with inductively coupled plasma (ICP-MS).Keywords: REE distribution • ultramafic and mafic rocks • accessory minerals © Versita Sp. z o.o.

Validity of the Apatite/Merrillite Relationship in Evaluating the Water Content in the Martian Mantle: Implications from Shergottite Northwest Africa (NWA) 2975

“…In the apatite/fluid interaction process, the REE partitioning is different from that occurring during apatite crystallization from melt [13,71]. Eu is more compatibly incorporated from fluids than from melts.…”

“…Both might be related to crystallization stimulated by local saturation in volatile contents with variable Cl and OH proportions. Such crystallization cannot be related to fractional crystallization of a mafic melt and instead requires open system conditions [13,15]. In Figure 9, the Cl-rich apatite composition falls into the assimilation field, suggesting assimilation of crustal material or interaction with fluids.…”

“…The Eu anomaly may denote a change in the oxygen fugacity during the crystallization process or may be derived from the order of the mineral fractionation [13,72]. It is difficult to relate the anomaly to oxygen fugacity because it was defined as changeable by He et al [30] during NWA 2975 basalt crystallization.…”

“…Phosphates that occur in extra-terrestrial mafic rocks may provide information regarding water (volatiles) content in the environment leading to their formation and transformation (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]). The magma source for Martian basalts is the Martian mantle; thus, the basaltic phosphates provide information on the Martian mantle composition as well as its evolution in the course of melting progression [11,[18][19][20][21].…”

On the Origin of Bastnaesite-(La,Nd,Y) in the Nissi (Patitira) Bauxite Laterite Deposit, Lokris, Greece

“…Recently, a review of the regularities of REE distribution in minerals contained in mafic and ultramafic rocks as accessory phases was performed [46]. These minerals include garnets, zircons, apatites and perovskites, which can accumulate high concentrations of REE in their structure, as well as chrome spinels, ilmenites, and micas which can accumulate, only limited contents of these trace elements [46]. In addition, the Europium in other samples (Table 6) is not depleted relative to neighboring REE (Sm and Gd) in the bulk ores, suggesting an original mantle source for the REE, since crustal rocks are mostly Eu-negative.…”