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V. V. Yarmolyuk D. A. Lykhin T. N. Shuriga A. A. Vorontsov A. M. Sugorakova 《Geology of Ore Deposits》2011,53(5):390-400
The Snezhnoe phenakite-beryl deposit is one of the highest-grade deposits in the Altai-Sayan beryllium province. This deposit
is spatially associated with the alkali granite of the Ognit Complex and localized in the apical part of the granitic pluton.
The trace element composition of granite, as well as of Be and Ta-Nb ores was studied. The Rb-Sr age of Be mineralization
estimated at 305 Ma is consistent with the time of formation of numerous rare-metal alkali granitic plutons in the Eastern
Sayan and the eastern Tuva. The region of these granitic plutons is outlined as the Late Paleozoic East Sayan rare-metal metallogenic
zone specialized for Nb, Ta, Be, Li, Zr, Th, and REE mineralization. The East Sayan zone is localized in the marginal part
of the Barguzin igneous province and is similar to the marginal zone of this province in composition of igneous associations
and metallogenic specialization. The formation of the Barguzin igneous province and the East Sayan metallogenic zone is related
to the evolution of the Late Carboniferous-Early Permian mantle plume. 相似文献
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The relationships between mineralization and magmatism during the formation of the Early Mesozoic West Transbaikal beryllium province are exemplified in the Urma helvite-bertrandite deposit. The deposit is drawn toward granitoids of elevated alkalinity, which belong to the Tashir Complex. Mineralization is related to leucogranite and characterized by patched distribution controlled by localization of metasomatic alteration. The latter is identified owing to replacement of feldspar with microcline and albite followed by silicification related to fracture zones. Helvite and bertrandite are the major Be minerals at the deposit. The Be grade of the ore is nonuniform and varies from 740 to 25000 ppm. Zircon, malacon, monazite, allanite, bastnaesite, columbite, and xenotime occur in metasomatic rocks together with Be minerals. Geochemical characteristics of alkali granites and metasomatic rocks are similar in a wide range of incompatible elements. Both are characterized by lowered Ba, Sr, P, and Eu contents and enriched in Th, U, Pb, Zr, and Hf. The degree of enrichment is the highest in the ore. The Be content in the ore correlates with concentrations of a number of other rare metals typical of host granite, which form their own mineralization against the background of metasomatic alteration, including Zr and REE minerals. Similarity in geochemistry of granitic rocks and Be ore indicates that the Urma deposit was related to the evolution of magmatic melt. Regional correlation shows that the ore-magmatic system of the Urma deposit is close to that of the Orot deposit, one of the largest in the central segment of the West Transbaikal metallogenic province. Both deposits are characterized by a similar composition of granitoids and comparable localization of ore zones in the structure of plutons. This similarity supports the high ore resource potential of Early Mesozoic alkali granites in the western Transbaikal region. Taking into account that these granitoids are widespread in the West Transbaikal Rift Zone that controls the metallogenic province, one can expect the discovery of new deposits therein. 相似文献
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D. A. Lykhin V. V. Yarmolyuk A. A. Vorontsov A. V. Travin 《Doklady Earth Sciences》2017,477(2):1379-1383
Geological, geochemical, and geochronological studies of rocks have been performed at the Okunyovo rare-metal ore magmatic complex (Western Sayan Mountains) composed of alkali granites and related F–Be mineralization. The geological data obtained and the features of the geochemical similarity of granite and ore mineralization identified are indicative of their genetic relation. Riebeckite from two granite samples has been subjected to 40Ar/39Ar analyses. The estimated age values of 481.5 ± 2.7 Ma and 486.5 ± 5.8 Ma are consistent within the limits of error and determine the age of Okunyovo alkali granite within 481–486 Ma ago. These data have made it possible to relate the studied rock and ore formation to the development of the Early Paleozoic ASFR controlled by the mantle plume. Along with the Okunyovo rare-metal granite massif, within the Sayan Region of the magmatic province, there are a number of Early Paleozoic alkali massifs related to the Aryskan, Raduga, and Kazyr rare-metal deposits. They are located in the conjugation area of the Western and Eastern Sayan ridges, in the Early Paleozoic Eastern Sayan rare-metal magmatism zone specialized in Be, W, Mo, Zr, Nb, and REEs. 相似文献
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I. K. Kozakov V. P. Kovach E. V. Bibikova T. I. Kirnozova D. A. Lykhin Yu. V. Plotkina E. V. Tolmacheva M. M. Fugzan Ch. Erdenezhargal 《Petrology》2014,22(5):480-506
The Early Caledonian Central Asian Orogenic Belt hosts fragments of continental blocks with Early and Late Precambrian crystalline basement. One of the structures with an Early Precambrian basement was thought to be the Dzabkhan microcontinent, which was viewed as an Early Precambrian “cratonal terrane”. The first geochronologic data suggest that the basement of the Dzabkhan microcontinent includes a zone of crystalline rocks related to Late Riphean tectonism. Geological, geochronological (U-Pb zircon dates), and Nd isotopic-geochemical data were later obtained on the northwestern part of the Dzabkhan microcontinent. The territory hosts the most diverse metamorphic complexes thought to be typical of the Early Precambrian basement. The complexes were determined to comprise the Dzabkhan-Mandal and Urgamal zones of high-grade metamorphic rocks. Gabbrodiorites related to the early metamorphic episode and dated at 860 ± 3 Ma were found in the Dzabkhan-Mandal zone, and the gneiss-granites marking the termination of this episode were dated at 856 ± 2 Ma. The granitoids of the Dzabkhan batholith, whose emplacement was coeval with the termination of the late high-grade metamorphic episode in rocks of both zones, have an age of 786 ± 6 Ma. Similar age values were determined for the granitoids cutting across the Late Precambrian rocks of the Songino and Tarbagatai blocks, which mark the stage when the mature Late Riphean continental crust was formed. The Late Riphean magmatic and metamorphic rocks of the Dzabkhan microcontinent were found out to have Nd model ages mostly within the range of 1.1–1.4 Ga at ?Nd(T) from +1.9 to +5.5. The Nd model age of the metaterrigenous rocks is 2.2?1.3 Ga at ?Nd(T) from ?7.2 to +3.1. The results of our studies provide evidence of convergence processes, which resulted in the Late Riphean (880?780 Ma) continental crust in Central Asia. Simultaneously with these processes, divergence processes that were responsible for the breakup of Rodinia occurred in the structures of the ancient cratons. It is reasonable to suggest that divergence processes within ancient continental blocks and Rodinia shelf were counterbalanced by the development of the Late Riphean continental crust in the convergence zones of its surrounding within established interval. 相似文献
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A. M. Sugorakova V. V. Yarmolyuk V. I. Lebedev D. A. Lykhin 《Doklady Earth Sciences》2011,439(2):1070-1075
Geological, petrologeochemical, and geochronological studies of the rocks from the Shivei alkali-granitic pluton were conducted.
A pluton about 500 km2 in area is a part of the larger (more than 30 000 km2) Kaakhem magmatic area. The data obtained allow us to characterize the magmatic complex of the Shivei pluton as a bimodal
association with picrobasalts, subalkali basalts, and subalkali and alkali granitic rocks differentiated from syenites to
leucogranites. The SHRIMP_II zircon dating from quartz syenites and alkali granites indicate the Permian age of the pluton
(293.8 ± 3.8 Ma and 297.1 ± 3.8 Ma, respectively). Mafic-alkali-granitic associations similar in age and type, which are traced
in the meridional direction along the Eastern Sayan toward the Siberian Platform, were distinguished as the Eastern Sayan
zone of the Late Paleozoic alkaline magmatism. Its location corresponds to the western periphery of the Angaro-Vitim batholite
and fits well into the zonal structure of the Barguzin magmatic province. We relate the geodynamic position of the Barguzin
province with the mantle plume that was overlapped by the edge of the Siberian Pale-ocontinent in the course of its Paleozoic
migration above the African hot spot. 相似文献
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A. A. Vorontsov V. V. Yarmolyuk D. A. Lykhin S. I. Dril S. A. Tatarnikov G. P. Sandimirova 《Petrology》2007,15(1):35-57
The Northern Mongolia-Western Transbaikalia rift zone is the largest Mesozoic riftogenic structure in eastern Asia and extends for a distance of more than 1200 km. The zone consists of depressions and grabens, which were formed between 233 and 188 Ma and are filled with basaltic and basalt-comendite (bimodal) volcanic associations accompanied by numerous peralkaline granite massifs. Geochemical and isotope (Sr, Nd, and Pb) studies showed that mantle and crustal sources contributed to the formation of the magmatic rocks of the rift zone. The basalts were formed from incompatible element-enriched mantle sources. Geochemical and isotope-geochemical data suggest that the peralkaline salic rocks (comendites and peralkaline grantoids) and basalts are genetically related and were formed by the fractionation of a common parental magma. In addition, the magmatic associations contain peralkaline granites and comendites whose isotope signatures indicate their formation through the crustal contamination of derivatives of basaltic melts. The rift zone has arisen during the formation of the Mongolia-Transbaikalia zoned magmatic area in a complex geodynamic setting, combining collision in the Mongolia-Okhotsk suture with a mantle plume impact. The rift zone occupies the northern periphery of the area, being controlled by the Northern Mongolia-Transbaikalia fault system, which marks the boundaries (sutures) of large terranes in the lithosphere. Asthenospheric traps beneath suture boundaries served as pathways for the penetration of a mantle plume into the upper lithosphere, thus playing an important role in the localization of the riftogenic processes. 相似文献
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Lykhin D. A. Yarmolyuk V. V. Nikiforov A. V. Kozlovsky A. M. Magazina L. O. 《Geology of Ore Deposits》2018,60(6):461-485
The role of magmatic differentiation is considered for the formation of the Ulan-Tologoi Ta–Nb–Zr deposit (northwestern Mongolia) related to the eponymous alkali granite pluton. Data are presented on the structure of the pluton, the composition of its rocks, and distribution of rare metal mineralization. The ores of the pluton include alkali granites with contents of ore elements exceeding the normative threshold for Ta (>100 ppm). The rare metal mineralization includes pyrochlore, columbite, zircon, bastnaesite, monazite, and thorite, which are typical of all alkali–salic rocks; however, their amount varies depending on the REE content of the rocks. The pluton was formed ~298 Ma ago under the influence of a mantle-crustal melt source.
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