RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 8, ES3002, doi:10.2205/2006ES000196, 2006

Typomorphic features of Cr-spinel and mineralogical prospecting guides for Cr ore mineralization

A. B. Makeyev

Institute of Geology, Komi Research Center, Ural Division, Russian Academy of Sciences, Syktyvkar, Russia


Contents


Abstract

[1]  Alpine-type dunite-harzburgite-lherzolite massifs have long attracted much attention of geologists as reference objects for geological and petrological models and as massifs hosting economic deposits of Cr, Ni, and asbestos. Russia's largest deposits of Cr ores, Ni ores in weathering crusts, as well as deposits PGE, asbestos, and some other minerals are hosted by Alpine-type ultrabasic massifs of the Urals. The results of our long-term fieldwork and of the experimental and theoretical research of the mineralogy, petrography, and metallogeny of Uralian Alpine-type ultrabasites and the analysis of literature data on analogous rocks elsewhere led us to the following conclusions. The evolution of the mineral assemblages of the Alpine-type ultrabasites occurred in six major stages: mantle, regional metasomatic, pegmatitic, retrograde and prograde metamorphic, and hypergenesis. The Alpine-type ultrabasites evolved during the metamorphic stage in a closed system and could exchange only energy with the environment. The driving forces of the evolution of the mineral assemblages were variations in the intensive parameters of the mineral-forming medium, namely, a temperature and pressure decrease, variations in the fluid regime and in the pH and Eh. Certain ranges of thermodynamic parameters, and thus, certain types of mineral assemblages, corresponded to the typomorphic rocks of each stage.


Introduction

[2]  Alpine-type dunite-harzburgite-lherzolite massifs are components of gabbro-ultramafic belts in mountaineous areas. They have long attracted much attention of geologists as reference objects for geological and petrological models and as massifs hosting economic deposits of Cr, Ni, and asbestos. Russia's largest deposits of Cr ores, Ni ores in weathering crusts, as well as deposits PGE, asbestos, and some other minerals are hosted by Alpine-type ultrabasic massifs of the Urals. Another noteworthy feature of these massifs in Urals, which are sometimes strongly altered and disturbed elsewhere, is a broad spectrum of metamorphic grades of these rocks, from unaltered varieties to eclogites, and their weak tectonic disturbance, which makes it possible to trace all alterations and transformation stages of the rocks themselves and their mineralogy. This applies, first of all, to the ultrabasic rocks in the Polar Urals (Figures 1-5).

[3]  We conducted topomineralogical studies of Alpine-type ultrabasic massifs in the Polar Urals for more than two decades with the aim of collecting materials on the compositions of the rocks and minerals, determining the crystallization successions and thermodynamic conditions of mineral assemblages and related complex ore mineralization. Our conclusions are based on more than 2500 chemical analyses of rocks, Cr-spinels, and rock-forming silicates [Bryanchaninova, 2004; Bryanchaninova et al., 2004a, 2004b; Makeyev, 1989, 1990, 1992a, 1992b, 1994; Makeyev and Bryanchaninova, 1999; Makeyev and Zaripova, 1984; Makeyev et al., 1982, 1984, 1984].

[4]  In this research we widely utilized microprobe analyses. We also examined the physical properties of minerals, including their magnetic susceptibility, unit cell parameters, dispersion of their reflectance, hardness, and density. Numerous IR spectroscopic determinations were carried out to evaluate the compositions of the accessory Cr-spinels. Selected samples were additionally studied by luminescence and absorption spectroscopy within the optical region, electronic microscopy of the ultrabasic rocks and their minerals, electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), nuclear gamma resonance (Mössbauer spectroscopy) of minerals, and the geochemistry of oxygen and carbon isotopes [Bryanchaninova et al., 2004a; Makeyev, 1989, 1990, 1992a, 1992b, 1994; Makeyev and Bryanchaninova, 1999; Makeyev and Zaripova, 1984; Makeyev et al., 1982, 1984, 1984].


Results and Discussion

[5]  The results of our long-term fieldwork and of the experimental and theoretical research of the mineralogy, petrography, and metallogeny of Uralian Alpine-type ultrabasites and the analysis of literature data on analogous rocks elsewhere led us to the following conclusions.

[6]  The evolution of the mineral assemblages of the Alpine-type ultrabasites occurred in six major stages: mantle, regional metasomatic, pegmatitic, retrograde and prograde metamorphic, and hypergenesis [Makeyev, 1992b; Makeyev and Bryanchaninova, 1999].

[7]  The Alpine-type ultrabasites evolved during the metamorphic stage in a closed system and could exchange only energy with the environment.

[8]  The driving forces of the evolution of the mineral assemblages were variations in the intensive parameters of the mineral-forming medium, namely, a temperature and pressure decrease, variations in the fluid regime and in the pH and Eh. Certain ranges of thermodynamic parameters, and thus, certain types of mineral assemblages, corresponded to the typomorphic rocks of each stage.

[9]  The lherzolites, diopside harzburgites, plagioclase lherzolites, bronzitites, and plagioclase-bronzite veins complimentary to the gabbro were produced during the first stage in the mantle. The P - T crystallization conditions of minerals and rocks during the first stage were evaluated by the pyroxene geothermometer at T =1200 pm 100o C and P =20 pm 5 kbar [Makeyev, 1992b; Makeyev and Bryanchaninova, 1999; Mercier, 1980].

[10]  The rocks of the dunite-harzburgite complex (dunites, harzburgites, and websterites), the dunite-wehrlite-clinopyroxenite complex, and the high-quality metallurgical Cr ores were produced during the regional metasomatic stage, which occurred at T = 900 pm 50o C and P = 12 pm 5 kbar.

[11]  Regional metasomatism resulted in the olivinization of the ultrabasites, with MgO and SiO2 becoming the major mobile components. The origin of large dunite masses was related to the accumulation of MgO and the removal of SiO2. The olivinization of the harzburgites and lherzolites was associated with the synchronous origin of clinopyroxenite and websterite veins in which excess components (CaO, Al2O3, and Na2O) were accumulated. Regional metasomatism facilitated the development of large economic deposits of Cr, whose ore mineral is chromite. The metasomatic genesis of the chromite follows from the existence of analogous metasomatic zoning (from top to bottom): harzburgite dunite chromite; an increase in the contents of ore Cr-spinel from the periphery to the cores of chromite bodies; the symmetric inner structures of the lens-shaped chromite bodies; the aureoles of lower Fe# of olivine around the chromite bodies; and other features.

[12]  Under the original P - T conditions ( T = 900 pm 50oC, and P = 12 pm 5 kbar), contact metasomatism proceeded along contacts of ultrabasites and gabbro. This Mg-Ca metasomatism produced the dunite-wehrlite-clinopyroxenite complex. Thus, the clinopyroxenite developed after gabbro and the dunite and wehrlite replaced harzburgite and lherzolite.

2006ES000196-fig06
Figure 6
[13]  We were the first to identify a pegmatite stage in the evolution of the ultrabasite rocks. This stage was responsible for the origin of pegmatoid dunite with early antigorite, whose water is likely of juvenile origin. The Cr-bearing silicates (kemmererite, kochubeite, amesite, uvarovite, and pargasite) crystallized in the Cr ores during this stage in fractures and small cavities. The rare mineral association of corundum with plagioclase should also be attributed to the pegmatite stage. This association with oligoclase, ruby, phlogopite, fishmanite (Sr-bearing mica), pargasite, Fe-Al chromite, and ferroaluminochromite occurs most widely at Rubinovyi Log in the central part of the Rai-Iz Massif. The rocks are ruby-bearing pegmatites (Figure 6). The ruby plagioclasites were dated by the K-Ar method on phlogopite at 320 pm 20 Ma. The typomorphic Cr-spinel of this association is ferrochromite (Fe6Mg2 )8 (Cr12.5Al3Fe0.5 )16O32. The occurrence of water-, chlorine- and fluorine-bearing minerals in this mineral assemblage suggests their crystallization in the presence of a pegmatite fluid [Bryanchaninova et al., 2004b; Makeyev, 1992b; Makeyev and Bryanchaninova, 1999].

[14]  X-ray diffraction data demonstrate that the antigorite forms syntactic aggregates with olivine. These syntactic intergrowths suggest that the antigorite and olivine crystallized in equilibrium with each other. This is the highest temperature generation of the antigorite, which likely crystallized at temperatures of no less than 700 pm 50oC. The contents of the primary antigorite in the pegmatoid dunites vary from 1% to 5%, and, hence, the water concentration in the fluid can be evaluated at 0.13 pm 0.65%. This was most probably juvenile water, which belonged to the ultrabasite system itself. Conversely, the serpentinization of olivine in the ultrabasite rocks proceeded under the effect of seawater [Bryanchaninova et al., 2004a].

[15]  The pegmatites were formed after the regional metasomatic stage, simultaneously with the solid-state (subsolidus) transformations of the rocks, their recrystallization with the participation of a fluid, and the accumulation of Ca, K, Na, Al, and Sr in the reaction products. All minerals of the ultrabasite rocks contain isomorphous Cr and are enriched in Al. We determined that the Rubinovyi Log pegmatites bear a new Sr-bearing mica, which contains 6% SrO [Bryanchaninova et al., 2004b].

2006ES000196-fig07
Figure 7
[16]  The main indicator of the mineral assemblages of Alpine-type ultrabasites is Cr-spinel, a mineral occurring in practically all rock varieties and having a composition and structure typomorphic of each of these varieties. The compositional evolution of the Cr-spinel (Figure 7) proceeded from Cr-picotite to chromite and then to magnetite and was associated with the depletion of Mg, Al, Zn, and Ni and enrichment of Fe (both Fe2+ and Fe3+ ), Mn, Ti, and V.

[17]  Cr-spinel is one of the most widely spread typomorphic minerals of ultrabasic rocks and is contained in each of them (it is a so-called telescoped mineral). Cr-spinel is also a major mineral of the Cr ores, and its contents vary from 0.1% to 2% in various rocks: dunites, harzburgites, lherzolites, wehrlites, websterites, pyroxenites, troctolites, and metamorphic ultrabasites. The contents of Cr-spinel in dunites often increases to 10%.

2006ES000196-fig08
Figure 8
2006ES000196-fig09
Figure 9
[18]  Cr-spinel grains broadly vary in shape and size: from dust-sized (0.001 mm) inclusions in silicates to large (5-25 mm) grains and their aggregates (Figures 8 and 9). Their shapes and color also vary. Anhedral transparent grains of Cr-spinel of color varying from yellowish green to brown were found only in the primary lherzolites and harzburgites. Equant reddish brown transparent grains are typical of the aluminochromite ores. Euhedral Cr-spinel crystals of octahedral habit, opaque (usually black) are contained in the secondary metasomatic rocks: dunites, pyroxenite veins, and high-Cr ores. Anhedral and skeletal crystals, which are sometimes replaced by serpentine and chlorite, are typical of accessory Cr-spinel in the metamorphic ultrabasites. Metamorphic Cr-spinel is usually black and opaque and often contains multiphase inclusions.

2006ES000196-fig10
Figure 10
[19]  The reflectance indices ( R ) of polished Cr-spinel grains and their microprobe analyses indicate that these grains are either homogeneous or zonal, with cores of primary composition and younger ferro-ferri Cr-spinel margins (Figure 10). Such grains are often surrounded by kemmererite rims (rinds) and consist of three zones: (i) cores, (ii) peripheral rims of ferrochromite, ferrichromite, and Cr-magnetite, (iii) and rinds of chlorite with magnetite dust.

2006ES000196-fig11
Figure 11
2006ES000196-fig12
Figure 12
2006ES000196-fig13
Figure 13
[20]  The composition of Uralian Cr-spinel varies within fairly broad ranges. We have compiled a database of analyses of Cr-spinel (more than 1000 chemical and microprobe analyses; Figures 11, 12, and 13). Most of these analyses characterized ultrabasite massifs in the Polar Urals [Makeyev, 1992b; Makeyev and Bryanchaninova, 1999]. The database also includes approximately 200 analyses of accessory and ore Cr-spinel from the Kempirsai, Sarany, Nizhnii Tagil, and Veresobyi Bor massifs, from the Western Sayan Range, and from some other territories [Makeyev and Bryanchaninova, 1999; Pavlov and Grigorieva-Chuprynina, 1973]. These analyses were used for comparison.

[21]  The composition of the ore Cr-spinel usually varies from Cr-picotite to chromite, and the composition data points plot near the left corner of N. V. Pavlov's triangular diagram [Pavlov and Grigorieva-Chuprynina, 1973]. Each of the massifs is characterized by its own variability ranges of the composition and physical properties of its Cr-spinel. We established two isomorphic trends for the ore Cr-spinel: Mg, Al Fe3+ and Mg, Al Fe2+, Fe3+. The former and latter trends characterize the primary and metamorphic ores, respectively. The accessory Cr-spinel is even more variable in composition. In Pavlov's triangular plot, the data points of the accessory Cr-spinel scatter not only in the left-hand part (as the ore Cr-spinel points do) but also extend into the right-hand part (Figures 11, 12, and 13). The most broadly variable composition is characteristic of Cr-spinel from the Syum-Keu, Rai-Iz, and Nizhnii Tagil massifs. Their metamorphic Cr-spinel is ferrochromite, ferrialuminochromite, ferrichromite, Cr-magnetite, and magnetite. The Voikar-Syninskii and Kempirsai massifs contain primary picotite, Cr-picotite, aluminochromite, and chromite. This reflects the intensity of metamorphic transformations of the ultrabasites of these massifs. The compositional variations of the accessory Cr-spinel were traced from picotite to chromite according to the following tendency: Mg, Al, Zn, Ni Cr, Fe2+, Fe3+, Mn, Ti, V. The Cr-spinel in the rocks of the mantle stage is picotite, Cr-picotite, and low-Cr aluminochromite; the rocks of the regional metasomatic stage contain high-Cr aluminochromite and chromite; the pegmatite-stage rocks bear ferro-aluminochromite and ferrochromite; and the rocks of the contact metamorphic stage contain ferro-feri Cr-spinel (Figure 7).

[22]  Microprobe analyses of one grain of accessory Cr-spinel from dunite of the Rai-Iz Massif revealed a zonal structure of this grain: it had a core of aluminochromite (Mg3.5, Fe4.5 )8 (Cr10.8 Al4.8 Fe0.4 )16 O32 and peripheral portions consisting of chromite (Mg3.2 Fe4.8 )8 (Cr12.0 Al3.5 Fe0.5 )16O32. This grain clearly illustrates the Mg, Al Cr, Fe compositional trend of the Cr-spinels and the original high-Al composition of the Cr-spinel with respect to the chromite. Other grains often display evidence of the exsolution of unstable ferrichromite and chrome-magnetite phases into ferrochromite and magnetite. This process can be expressed by the scheme: ferrochromite (Cr, Zn) ferrichromite, Cr-magnetite (Al, Fe2+, Mg - const) magnetite (Fe3+, Mn, V, Ti).

[23]  It is now quite obvious that ferrochromite (Fe6 Mg2 )8 (Cr12 Fe3 Al)16O32, magnetite (Fe6 Mg2 )8 (Fe12-15 Cr4-1 )16O32 could crystallize in ultrabasite rocks only during prograde metamorphism, at relatively low temperatures.

[24]  The series of spinel MgAl2O4 and magnetite FeFe2O4 is known to have a miscibility gap.

2006ES000196-fig14
Figure 14
2006ES000196-fig15
Figure 15
2006ES000196-fig16
Figure 16
[25]  Together with L. D. Zaripova of the Kazan State University [Makeyev, 1992a, 1992b; Makeyev and Zaripova, 1984], we examined the Mössbauer spectra of approximately 100 samples of natural primary and metamorphosed Cr-spinels from the Rai-Iz Massif. The composition and some other characteristics of some of these samples are listed in Table 1. The ferrichromites and chrome-magnetites were determined to consist of two phases and display a broad compositional miscibility gap in the chromite-magnetite series (Figures 14, 15, and 16). The dependence of the quadrupole split ( D E) of iron ions at three sites ( BFe3+, BFe2+, and AFe2+ ) on the Al mole fraction [Al/(Al + Cr)] in the Cr-Al Cr-spinel series (chromite-picotite, where Fe3+<1 f.u.) can be expressed in the form of the following two linear and one quadric regression equations:

DE = 1.075 [Al/(Al + Cr)] + 0.578  mm s-1 (B Fe3+),

DE = 0.345 [Al/(Al + Cr)] + 0.469  mm s-1 (B Fe2+),

DE = -3.736 [Al/(Al + Cr)]2

+ 4.047 [Al/(Al + Cr)] + 0.572  mm s-1 (AFe2+).

[26]  The exsolution of the Cr-spinel solid solution in the chromite-magnetite series was also confirmed by the data of IR spectroscopy, magnetic susceptibility, and, for some samples, by their microprobe analyses. Occasional finds of ferrichromite and chrome-magnetite, which are identified by chemical analyses, should be attributed to natural mixtures with variable proportions of two members of the ferrochromite-feromagnetite series on a microscopical (cluster) scale.

2006ES000196-fig17
Figure 17
[27]  This newly discovered miscibility gap in the chromite-magnetite series is shown in a spinel-hercynite-magnetite-magnesiomagnetite-magnesiochromite-chromite diagram (Figure 17). As can be seen from this Figure, only three of the end members (spinel, hercynite, and magnetite) were found in nature, and none of the other end members is known to occur in natural rocks. Hence, we were the first to constrain the stability region of the limited solid solution of natural Cr-spinels. This region is bounded by a complicatedly curved surface within a tetrahedral compositional diagram and includes two miscibility gaps.

2006ES000196-fig18
Figure 18
2006ES000196-fig19
Figure 19
2006ES000196-fig20
Figure 20
[28]  We examined the typomorphic features of the composition and properties of natural Cr-spinels (Figures 18, 19, and 20). The following regression equations can be proposed to relate the composition of this mineral to its unit-cell parameter a 0, wavelength of the IR spectrum n1, and the reflectance R:

a0 (Å) = 8.162 - 0.0098times Mg2+ + 0.0146times Cr3+ + 0.0139 times Fe3+,

n1 ( cm-1) = 671.8 + 0.580times Mg2+ - 3.268 times Cr3+ - 1.607times Fe3+,

R (%) = 9.872 - 0.406times Mg2+ + 0.369times Cr3+ + 0.605 times Fe3+.

[29]  Other indicator minerals of Alpine-type ultrabasites are olivine, clinopyroxene, plagioclase, pentlandite, and some others. Their composition and physical characteristics vary during the evolution of the rocks similarly to those of the Cr-spinel. These minerals can also be utilized for the purposes of genetic analysis and petrological reconstructions.

[30]  The results of our research allowed us to identify new mineralogical indicators and propose new criteria for the assessment of the occurrences and deposits of Cr ore mineralization related to Alpine-type ultrabasites. The first of them is a correlation between the compositions of the accessory and ore Cr-spinels. This criterion makes it possible to predict the composition of Cr-spinel in concealed and unidentified orebodies. The composition of the ore Cr-spinel is correlated with the composition of the accessory Cr-spinel, a mineral that is contained in practically all of the rocks. The other criterion is the concentration of the fayalite end member of the rock-forming olivine (or the index of refraction Ng of this olivine), which decreases toward orebodies and zones with Cr ore mineralization [Bryanchaninova and Makeyev, 1988]. The third criterion is the mineral assemblages of the rocks, the compositions of the typomorphic minerals, and the spatial distribution of ultrabasite complexes, with this criterion making it possible to assay the possible reserves of the Cr ores.

[31]  Our data on accessory and ore Cr-spinel in ultrabasites from the Polar Urals indicate that the composition of this mineral seems to be a sensitive indicator of prograde metamorphism but is almost insusceptible to retrograde metamorphism. The prograde metamorphism of ultrabasites to the amphibolite and greenschist facies transforms and recrystallizes their accessory Cr-spinel and is favorable for its depletion in Cr and Al, the oxidation of its Fe2+ to Fe3+, and, eventually, in enrichment of the mineral in the magnetite end member. The final metamorphic product of the accessory Cr-spinel is newly formed magnetite and kemmererite, which concentrates some Al and Cr removed from Cr-spinel.

[32]  The analysis of our data led us to identify two trends in the correlations between the compositions of ore and accessory Cr-spinel in chromite-bearing ultrabasites.


Conclusion

2006ES000196-fig21
Figure 21
[33]  Our materials on the rocks of the lherzolite-harzburgite, dunite-harzburgite, and dunite complexes (which are either not altered at all or were affected only by retrograde metamorphism) suggest a weak correlation between the compositions of their ore and accessory Cr-spinels: dunites contain high-Cr accessory Cr-spinel-chromite, and lherzolites and harzburgites contain, respectively, high-Al aluminochromite and Cr-picotite (Figure 21). A striking example of the aforesaid is offered by the Kempirsai Massif [Pavlov and Grigorieva-Chuprynina, 1973]. Other ultrabasites metamorphosed during the retrograde stages show some inconsistencies between the compositions of their ore and accessory Cr-spinels. This can be illustrated by the examples of the Tsentralnoe and Zapadnoe economic deposits of high-Cr ores of the Rai-Iz Massif, whose orebodies consisting of chromite and subferrialuminochromite are hosted by rocks with metamorphic accessory spinel of high-Fe composition: ferro-ferri Cr-spinel (Figure 22).

2006ES000196-fig22
Figure 22
2006ES000196-fig23
Figure 23
[34]  An efficient method for the evaluation of the Cr2O3 concentration in spinel is infrared spectroscopy. The position of IR absorption bands in the spectra depends on the composition of the Cr-spinel, and this makes it possible to rapidly and accurately enough evaluate the Cr2O3 concentrations in large collections of samples. In the course of studying the Polar Urals, we have obtained and interpreted more than 10000 IR spectra of Cr-spinels. Maps were prepared (Figures 22 and 23) that show the variability of this parameter over an area of approximately 2000 km2 for all of the three massifs in the Polar Urals [Makeyev, 1990, 1992a, 1992b; Makeyev and Bryanchaninova, 1999].

2006ES000196-fig24
Figure 24
2006ES000196-fig25
Figure 25
[35]  We conducted mineralogical mapping at these three ultrabasite massifs in the Polar Urals: Syum-Keu, Rai-Iz, and Voikar-Syninskii. Figures 22, 23, 24, and 25 demonstrate the potentialities of large-scale mineralogical mapping, as illustrated by the example of application of these techniques at the Rai-Iz Massif. The reader can find all other mineralogical and prediction maps for the whole Polar Uralian ultrabasite belt in the monograph [Makeyev and Bryanchaninova, 1999]. The criteria used for the mapping included the dunite constituent (Figures 22a, 23b, and 24) in the rock complexes (this was the basis used to prepare the geological maps of the ultrabasite massifs), the Fe mole fraction (Figures 22b and 25b) of the rock-forming olivine (this parameter was evaluated from the indices of refraction of this mineral or was calculated from its microprobe analyses and makes it possible to reliably localize orebodies), and IR spectroscopic data (Figures 22d, 23d, 25a, and 25b) on the accessory and ore Cr-spinel (these data allowed us to assay the composition the quality of the Cr ores). The materials were generalized in the form of a prediction map of the chromite potential of the massif (Figure 25d).

[36]  Areas highly promising for exploration for chromite ores are those where the dunite-harzburgite complex with high dunite contents contains accessory Cr-spinel corresponding to chromite or ferrichromite in composition (with the n1 parameter of the IR spectra ranging from 620 cm-1 to 635 cm-1 ). The Cr concentration in the accessory Cr-spinel of the dunites increases toward chromite orebodies. Conversely, the areas (fields) of the harzburgite and dunite-harzburgite complexes with low dunite contents and high Al concentrations in the accessory Cr-spinel (with the n1 parameter lower than 600 or higher than 640 cm-1 ) are not promising as exploration targets for Cr ore mineralization.

[37]  Blocks of ultrabasite rocks most promising for exploration for large deposits are those with large dunite bodies and with adjacent fields of the dunite-harzburgite complex containing much dunite. These areas are characterized by low contents of pyroxene in the harzburgite (10-12%), accessory Cr-spinel high in Cr, and relatively Fe poor olivine from the dunite composing the ore zone.


Acknowledgments

[38]  I am thankful and indebted my colleagues N. I. Bryanchaninova, T. N. Oleinikova, A. S. Varlakov, G. N. Modyanova, L. D. Zaripova, T. N. Popova, T. D. Kosareva, O. V. Koksharova, and many others for help with the analytical studies and for fruitful discussion of the results of this research, with these discussions greatly assisting in the successful completion of this work.


References

Bryanchaninova, N. I. (2004), Serpentines and serpentinites of the Urals, Ph. D., 44 pp., Komi Filial Akad. Nauk, Syktyvkar.

Bryanchaninova, N. I., and A. B. Makeyev, (Eds.) (1988), Techniques of exploration for concealed chromite ore mineralization, in: A.S. no. 1405008 (USSR), kl. G01/09/00, p. 66, Komi Filial Acad. Nauk, Syktyvkar.

Bryanchaninova, N. I., E. O. Dubinina, and A. B. Makeyev (2004a), Geochemistry of hydrogen isotopes in chromite-bearing ultrabasites of the Urals, Dokl. Ross. Akad. Nauk, 395, (3), 392.

Bryanchaninova, N. I., A. B. Makeyev, N. V. Zubkova, and V. N. Filippov (2004b), Na-Sr mica Na 0.50 Sr 0.25 Al 2 (Na 0.25-0.75 )[Al 1.25 Si 2.75 O 10 ](OH) 2 from Rubinovyi Log, Dokl. Ross. Akad. Nauk, 395, (1), 101.

Makeyev, A. B. (1989), Criteria for the prediction of deep-sitting chromite ore mineralization, in: Problems of the Economics of Mineral Resources of the Tiamn-Pechora Fuel and Industrial Complex, p. 32, Komi Filial Akad. Nauk SSSR, Syktyvkar.

Makeyev, A. B. (1990), Typomorphic features of Cr-spinels and their utilization in mineralogical mapping, in: Physics of Minerals and Their Analogues, p. 53, Nauka, Leningrad.

Makeyev, A. B. (1992a), Mineralogy of Alpine-Types Ultrabasites in the Urals, 197 pp., Nauka, St. Petersburg.

Makeyev, A. B. (1992b), Evolution of Mineral Assemblages of Alpine-Type Ultrabasites in the Urals, Ph. D., 46 pp., Nauka, St. Petersburg.

Makeyev, A. B. (1994), Modes of Pt occurrence in Alpine-type ultrabasites, in: Geology and Genesis of PGE Deposits, p. 175, Nauka, Moscow.

Makeyev, A. B., and N. I. Bryanchaninova (1999), Topomineralogy of Ultrabasites in the Polar Urals, 252 pp., Nauka, St. Petersburg.

Makeyev, A. B., and L. D. Zaripova (1984), Mössbauer spectroscopy of naturally occurring Ti-bearing ferrialuminochromites and ferroferri-Cr-spinels, Dokl. Akad. Nauk SSSR, 275, (4), 974.

Makeyev, A. B., L. V. Agafonov, and A. I. Goncharenko (1984), Relations between the chemical composition and physical properties of Cr-spinels from Alpine-type ultrabasites, Geol. Geofiz., 25, (2), 132.

Makeyev, A. B., E. B. Bushueva, and B. V. Perevozchikov (1982), IR spectroscopy of Cr-spinels as a method for revealing topomineralogical relations and the predicting assessment of chromite-bearing massifs, in: New Mineralogical Methods in Geological Prospecting, Trudy Instituta Geologii, vol. 38, p. 48, Komi Filial Akad. Nauk SSSR, Syktyvkar.

Makeyev, A. B., B. V. Perevozchikov, and A. K. Afanasiev (1985), Chromite Potential of the Polar Urals, 152 pp., Komi Filial Akad Nauk SSSR, Syktyvkar.

Mercier, I.-C.C. (1980), Single-pyroxene thermobarometry, Tectonophysics, 70, (1-4), 1. [CrossRef]

Pavlov, N. V., and I. I. Grigorieva-Chuprynina (1973), Persistent Genetic Relations in the Genesis of Chromite Deposits, 199 pp., Nauka, Moscow.

Schteinberg, D. S., and K. K. Zoloev, (Eds.) (1985), Alpine-Type Hyperbasites of the Urals: Information Materials, 66 pp., UrO RAN, Sverdlovsk.


Received 15 January 2006; revised 19 January 2006; accepted 1 February 2006; published 15 July 2006.

Keywords: alpine-type massifs, orogenic belts, petrology, Urals.

Index Terms: 1009 Geochemistry: Geochemical modeling; 1020 Geochemistry: Composition of the continental crust; 1090 Geochemistry: Field relationships; 3617 Mineralogy and Petrology: Alteration and weathering processes.


RJES

Citation: Makeyev, A. B. (2006), Typomorphic features of Cr-spinel and mineralogical prospecting guides for Cr ore mineralization, Russ. J. Earth Sci., 8, ES3002, doi:10.2205/2006ES000196.

Copyright 2006 by the Russian Journal of Earth Sciences
Powered by TeXWeb (Win32, v.2.0).