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Petrographic thin-sections of titanite (Ttn), muscovite (Ms) and calcite (Cal) grains intergrown with larger plagioclase (Pl) crystals in plane-polarized light (A,C) and under crossedpolarized light (B,D); corundum (Crn) intergrowths with margarite (Mrg) and plagioclase crystals (E,F), plane-polarized light.
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The Snezhnoe ruby deposit is located in the Muzkol–Rangkul anticlinorium within the Cimmerian zone of the Central Pamir. On the local scale, the deposit occurs on discrete relict bedding planes of calcitic marbles belonging to the Sarydzhilgin suite. Four ruby-bearing mineral assemblages are present within the main parts of the deposit: 1) scapolit...
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... forms small-to medium-sized flaky aggregates ranging from ~1 to 4 mm. It is also found as inclusions in plagioclase and scapolite group minerals and in ruby ( Figure 5, Table S2). It is rarely replaced by the chlorite group minerals, likely clinochlore containing up to 25.35 wt% SiO2, 22.52 wt% Al2O3, 22.45 wt% FeO, 13.98 wt% MgO, 1.35 wt% Cr2O3 [11] and forming thin films on the surface of muscovite or infilling fractures in corundum. ...
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Three Mo-bearing granitic intrusions, namely: Gattar, Abu Harba, and Abu Marwa occur in the Gattar area in the North Eastern Desert of Egypt. These late tectonic granites intrude Neoproterozoic rocks of island arc metavolcanics and metagabbro-diorite complexes in addition to post-collision molasse-type sediments (Hammamat Group) and Dokhan-type vol...
Citations
... Большое значение в образовании месторождений корундов отводится кайнозойскому альпийскому орогенезу, с которым связаны тектонические события в Альпах, Родопах и Гималаях, т. е. от 55 млн лет до четвертичного периода. В гималайских мраморных метаморфических блоках месторождения рубина претерпели крупные тектонические события при столкновении Индийской и Азиатской плит Litvinenko et al., 2020]. ...
... Except for Pb and U loss (or increase) in zircon, and instrumental problems, the inherent age of the sample will influence the age dating (Machado & Simonetti 2001). Since 207 Pb is generally considered to be the least abundant isotope of zircon, it is also the isotope that is most impacted by even minute amounts of common Pb (Garnier et al. 2005;Litvinenko et al. 2020). For young zircon, the small amount of radiogenic 207 Pb is difficult to measure (because the Pb content may be close to the detection limit), and the signal-to-noise ratio of 206 Pb and 207 Pb may be poor during laser ablation (Hirata & Nesbitt 1995, Iizuka & Hirata 2004Sakata et al. 2014). ...
... The crystallization temperatures were estimated in the range of 710 -850 °C using a Zr-in-rutile thermometer (Litvinenko et al. 2020). This temperature range is close to those at 600 -650°C detected previously by thermodynamic modelling of mineral equilibria in the system CaO-SiO2-Al2O3-Na2O-K2O (Dufour et al. 2007) but well above those at 400 -450 °C estimated by micro-thermometry of fluid inclusions (Kievlenko 2003). ...
... This temperature range is close to those at 600 -650°C detected previously by thermodynamic modelling of mineral equilibria in the system CaO-SiO2-Al2O3-Na2O-K2O (Dufour et al. 2007) but well above those at 400 -450 °C estimated by micro-thermometry of fluid inclusions (Kievlenko 2003). In situ LA-ICP-MS U-Pb dating of the rutiles showed discordant ages with lower intercept on Concordia at 14 ±11 Ma (Litvinenko et al. 2020). This age is close to the 7 -16 Ma age recorded by K/Ar isotopic system in muscovites (Dmitriev & Ishan-Sho 1987) and may represent the last reactivation of geochronological records in these minerals linked to post-collision (or cooling) stage of Himalayan orogeny (50 Ma -Quaternary) in the area of Eastern Pamirs. ...
Ruby (Cr-bearing corundum) deposits typically occur in the continent-continent collision zones. Hence, their formation can be caused by several different processes over various timescales. It makes reconstruction of ruby mineralization quite challenging. Here we focus on Snezhnoe metamorphic marble-hosted ruby deposit from Eastern Pamir of the Himalayan orogeny. Despite numerous studies, its proposed age and formation conditions remain poorly understood. To solve these tasks, we used rutile (TiO 2) inclusions within ruby host and rutile grains from the bearing rocks (mica schists) in Snezhnoe deposit. The crystallization temperatures were estimated in the range of 710-850 °C using a Zr-in-rutile thermometer (Litvinenko et al. 2020).
... In contrast, Terekhov et al. (1999) argued that the Al is from magmatic fluid associated with alkaline intrusions. Metapelite or meta-bauxite were suggested to be the possible protoliths for the rubybearing rocks in Snezhnoe, Tadjikistan (Litvinenko et al. 2020). In the Goat claims occurrence in British Columbia, silicate layers and gneiss were suggested as the source of the Cr (Dzikowski et al. 2014, Giuliani et al. 2020. ...
... (3) Al and Cr are sourced from clay minerals deposited simultaneously with the carbonates and evaporite lenses (Garnier et al. 2008, Giuliani et al. 2015. (4) Al and/or Cr are sourced from silica layers and gneiss intercalated with marble (Dzikowski et al. 2014) or ancient Al-enriched sediments intercalated in the marbles (Litvinenko et al. 2020) (for a review, see Giuliani et al. 2020). ...
... This suggests that the elements necessary for the Yuanjiang ruby formation, i.e., Al and Cr, could originate from impure components (e.g., Al-and Cr-bearing detrital minerals; Garnier et al. 2008 within the carbonates. Therefore, the Yuanjiang deposit does not contradict the genetic models of Okrusch et al. (1976), Litvinenko et al. (2020), and Garnier et al. (2008), but also does not support the hypotheses of Terekhov et al. (1999) and Dzikowski et al. (2014). The formation of the Yuanjiang deposit is more consistent with the genetic model proposed by Garnier et al. (2008) from the following observations: ...
The Yuanjiang marble-hosted ruby deposit lies in the central segment of the Ailao Shan metamorphic massif of the Ailao Shan-Red River metamorphic belt. The mineralizing fluid and age were characterized by detailed petrography, Raman spectroscopy, microthermometry, and in situ titanite laser ablation-inductively coupled plasma-mass spectrometry dating. Some fluid inclusions in the corundum show an interesting morphology with a diaspore crystal fully separating the whole inclusion into two smaller inclusions. This morphological feature can be explained by morphological ripening and subsequent reactions between the trapped H2O and the host corundum during the cooling of the inclusion. Fluid inclusions in the ruby belong to the system CO2–H2S–COS–S8–H2S2–CH4–AlO(OH) with various daughter minerals, including diaspore, gibbsite, and native sulfur (S8). The observed seven-component fluid inclusion composition can be explained by two steps: (1) original fluid inclusion capture during deposit formation with compositions including CO2, H2S, COS, CH4, S8, and H2S2, and (2) post-entrapment fluid inclusion modification, such as diaspore and gibbsite. The presence of hydrous minerals in fluid inclusions strongly supports the idea that water was once present in the initial fluids.
In the Yuanjiang deposit, petrographic evidence shows that titanite formed simultaneously with ruby, and U-Pb dating of titanite allows us to conclude that the ruby mineralization formed at 23.4 ± 0.3 Ma, in other words during the Himalayan orogeny.
... However, these discriminant diagrams have weaknesses and should be used with caution, especially when applied to rubies (e.g., Palke et al. 2018, Sorokina et al. 2019, Krebs et al. 2020. For example, some Snezhnoe rubies of metamorphic origin fall into the ''magmatic'' domain in the Fe versus Ga/Mg diagram (Litvinenko et al. 2020). Here, the Yuanjiang ruby data was plotted in the diagrams related to host rock lithologies. ...
... The types of ruby deposits are as follows: Palin -alkali basalts-related; Mbuji-Mayi -kimberlite-related; Vohitany -rubies in maficultramafic rocks (M-UMR) (amphibolite-type); John Saul mine -rubies in plumasites; Mogok, Mong Hsu, and Quy Chaurubies in marbles. Trace element data for Aappaluttoq rubies of amphibolite-type(Keulen et al. 2020b) and marble-hosted rubies(Krebs et al. 2020, Litvinenko et al. 2020 are also shown in this plot.FIG. 21. ...
Primary rubies in the Ailao Shan of Yunnan Province, China, are found in three layers of marble. However, the origin and source rocks of placer rubies in the Yuanjiang area remains unclear. Trace element geochemistry and inclusion mineralogy within these materials can provide information on their petrogenesis and original source. Zircon, rutile, mica group minerals, titanite, and apatite group minerals were the main solid inclusions identified within the placer Yuanjiang rubies, along with other mineral inclusions such as pyrite, pyrrhotite, plagioclase group minerals, and scapolite group minerals. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurements showed that the placer rubies are characterized by average values of Mg (31 ppmw), Ti (97 ppmw), V (77 ppmw), Cr (3326 ppmw), Fe (71 ppmw), and Ga (66ppmw). A trace-element oxide diagram, Fe values (<350 ppmw), and the mineral inclusion assemblage suggest marble sources for the placer ruby. Therefore, the Yuanjiang rubies (both primary and placer) are metamorphic, and this fits well with the observations that skarn and related minerals are mostly absent in this deposit.
Yuanjiang rubies can be readily separated from the high-iron rubies of different geological types by their Fe content (<1000 ppmw). The discriminators Mg, Ga, Cr, V, Fe, and Ti have potential in separating Yuanjiang rubies from some other marble-hosted deposits, such as Snezhnoe. Nevertheless, geographic origin determination remains a challenge when considering the similarities in compositional features between the Yuanjiang rubies and rubies from some other marble-hosted deposits worldwide (e.g., Luc Yen). The presence of kaolinite group minerals and clusters of euhedral, prismatic zircon crystals in ruby suggest a Yuanjiang origin.
... A later tectonic event is linked to the Indian plate collision with Eurasia and formation of the Alpine-Himalayan orogenic belt at 45 Ma -Quaternary (Giuliani et al., 2014). The related corundum deposits are located from Tajikistan (Litvinenko et al., 2020) to Vietnam and are typically hosted by metamorphosed carboniferous sediments (marbles) . They share similar mineralogy and age constrains from 40 Ma to 5 Ma (Ar-Ar dating of mica and U-Pb analyses of different inclusions within ruby) corresponding to the Alpine-Himalayan collision time (Gübelin, 1982;Kammerling et al., 1994;Smith et al., 1997;Bowersox et al., 2000;Garnier et al., 2005Garnier et al., , 2006Khoi et al., 2011;Sorokina et al., 2015;Sutherland et al., 2019, etc.). ...
Metamorphic gem corundum (mainly ruby) deposits are robust indicators of continent-continent collision processes. However, a systematic link of primary magmatic blue sapphire occurrences to orogenic belts is less understood. An example is the Ilmenogorsky alkaline complex, within the Ilmen Mountains region and part of the Uralian orogenic belt. The mobile belt is a product of the collision among Kazakhstania, Laurussia, and Siberia continents prior to the closure of the Paleo-Uralian ocean and formation of the Laurasia supercontinent (330 – 250 Ma). It is believed that the alkaline complex became inсluded into the separate Sysertsk-Ilmenogorsk microcontinent with unconstrained borders, when sandwiched between Kazakhstania and Laurussia during that collision. Paleo-reconstructions illustrate that magmatic and metasomatic sapphire deposits linked to alkaline magmatism trace the natural boundary of the “lost” microcontinent with a high precision. The syenite pegmatites of alkaline complex carried unusually large corundum-blue sapphire megacrysts that have recorded the multi-stage development of the Ilmenogorsky complex. The deposits were formed at about 275 – 295 Ma ago as reconstructed by in situ LA-ICP-MS U-Pb zircon dating. This formation stage corresponds to a broader continental collision process followed by the formation of Uralian orogeny in the area of the Ilmenogorsky complex. One pegmatite deposit, the “298” mine, is characterized by the occurrence of unusually large corundum megacrysts. The analyses of Rb-Sr isotopic system in the rocks from this deposit revealed two isochrons at 249 ± 2Ma and 254 ± 22 Ma implying a late stage modification of original pegmatites. The timing of this stage corresponds to the limited post-collision stretching time. Hence, corundum-blue sapphire studied from magmatic (syenites) and metasomatic rocks linked to alkaline rocks in Uralian orogen suggests as a promising indicator for constraining the timing of continent-to-continent collision processes. https://authors.elsevier.com/a/1cTnI,UYEnYIXY
... This not only provides a solid foundation on the mineralogy and geochemistry involved in this gem varietal, but also presents an encompassing survey of its global deposits through historic and geological time. From this supporting synthesis, the satellite papers present their own particular points of interest that carry the ruby theme into new research territory [8][9][10][11][12][13]. Research into gem corundum, however, is a continuing process, and new aspects are already appearing since publication of the papers in the Special Issue. ...
... In a detailed study of the Snezhnoe ruby deposit, Central Palmir Mountains, Tajikistan, Litvenoko et al. [12] describe four ruby-bearing host assemblages intercalated within ruby-free assemblages. An introduction sets out the mineralogy of ruby as a corundum variety, aspects of ruby mineralization and the tectonic processes that make reconstructions of ruby formation a challenge. ...
... Rutile grains inter-grown with zircon enabled thermometry and indicated a T range of~830 ± 60 • C. Rb-Sr isotope results on ruby-bearing rocks plotted in a 87 Sr/ 86 Sr plotted in a figure indicated two error isochrones, one at 12 ± 3.0 Ma and another at 23 ± 1-2 Ma, the latter likely linked to alteration opening up the Rb-Sr system in phlogopite. An Nd isotopic result gave a bulk rock εNd (20 ma) value of −9.6 [12]. ...
Ruby as a natural gemstone has an early history in which its colorful properties [...]
... Examples include the marble-hosted ruby deposits in Campo Lungo (Switzerland) and Xanthi (Greece), and in Central and South-East Asia. In the Himalayas, the ruby deposits in marble occur in metamorphic blocks that were affected by major tectonic events during the collision of the Indian and Asian plates [131][132][133][134]. The ruby has been indirectly dated by 40 Ar/ 39 Ar stepwise heating experiments performed on single grains of coeval phlogopite, and by ion-probe U-Pb analyses of zircon included in the corundum [40,88,106,135]. ...
... The ruby has been indirectly dated by 40 Ar/ 39 Ar stepwise heating experiments performed on single grains of coeval phlogopite, and by ion-probe U-Pb analyses of zircon included in the corundum [40,88,106,135]. Other indirect dating for the Snezhnoe deposits in Central Pamir was realized on bulk rock (ruby-bearing phlogopite-plagioclase rocks) by the Rb-Sr method [134]. The Rb-Sr errorchron age yielded 23 ± 1.6 Ma, which had to be considered as a minimum age for ruby formation. ...
... Ruby and pink corundum deposits hosted in marbles are known from Asia [5,30,65,103,112,115,134,[207][208][209][210], North America [113,211], Europe [95,110], and Africa [48,110,114,182] (see Figure 2). These ruby deposits are hosted by meta-pure or impure limestone of carbonate platforms and are of two types: (1) in marble where the gem corundum crystallized as a result of prograde and retrograde isochemical metamorphic reactions, mainly in a closed system, and where the ruby occurs as disseminated crystals in marble, in Central and Southeast Asia and other places worldwide [65]; and (2) in impure marble containing gneiss and silicate layers where the ruby crystallized at the peak of prograde metamorphism, such as at Revelstoke in Canada [113,212], Snezhnoe in Tadjikistan [115,134], and Morogoro in Tanzania [114,163]. ...
Corundum is not uncommon on Earth but the gem varieties of ruby and sapphire are relatively rare. Gem corundum deposits are classified as primary and secondary deposits. Primary deposits contain corundum either in the rocks where it crystallized or as xenocrysts and xenoliths carried by magmas to the Earth’s surface. Classification systems for corundum deposits are based on different mineralogical and geological features. An up-to-date classification scheme for ruby deposits is described in the present paper. Ruby forms in mafic or felsic geological environments, or in metamorphosed carbonate platforms but it is always associated with rocks depleted in silica and enriched in alumina. Two major geological environments are favorable for the presence of ruby: (1) amphibolite to medium pressure granulite facies metamorphic belts and (2) alkaline basaltic volcanism in continental rifting environments. Primary ruby deposits formed from the Archean (2.71 Ga) in Greenland to the Pliocene (5 Ma) in Nepal. Secondary ruby deposits have formed at various times from the erosion of metamorphic belts (since the Precambrian) and alkali basalts (from the Cenozoic to the Quaternary). Primary ruby deposits are subdivided into two types based on their geological environment of formation: (Type I) magmatic-related and (Type II) metamorphic-related. Type I is characterized by two sub-types, specifically Type IA where xenocrysts or xenoliths of gem ruby of metamorphic (sometimes magmatic) origin are hosted by alkali basalts (Madagascar and others), and Type IB corresponding to xenocrysts of ruby in kimberlite (Democratic Republic of Congo). Type II also has two sub-types; metamorphic deposits sensu stricto (Type IIA) that formed in amphibolite to granulite facies environments, and metamorphic-metasomatic deposits (Type IIB) formed via high fluid–rock interaction and metasomatism. Secondary ruby deposits, i.e., placers are termed sedimentary-related (Type III). These placers are hosted in sedimentary rocks (soil, rudite, arenite, and silt) that formed via erosion, gravity effect, mechanical transport, and sedimentation along slopes or basins related to neotectonic motions and deformation.
The article presents the results on the chemical and morphological research of corundum crystals (α-Al2O3) from several African, Asian, and Russian deposits. The trace- elements of interest were determined by rim-to-rim laser ablation-inductively coupled plasma- mass spectrometry and electron micro-probe analyses coupled to Cr3+ photoluminescence mapping. The variations of corundum morphology are directly linked to a distinct range of Cr and Fe values. Chromium ions, which are larger than Al ions, when substituting in the crystal structure, elongate it along the prismatic face or the c axis. Whereas the fastest growth of the bipyramidal faces is linked to the co-introduction of Cr and Fe ions. The higher amount of Fe comparing to Cr (3: 1 and more) leads to faster growth of the rhombohedron and pinacoid faces.
