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Some Notes on the Lugiin Gol, Mushgai Khudag and Bayan Khoshuu Alkaline Complexes, Southern Mongolia  [PDF]
Munkhtsengel Baatar, Gerel Ochir, Jindrich Kynicky, Shigeru Iizumi, Piero Comin-Chiaramonti
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.48114
Abstract:

Volcanic-plutonic alkaline complexes from Lugiin Gol, Mushgai Khudag and Bayan Khoshuu, southern Mongolia (244, 139 and 131 Ma, respectively) occur within grabens in E-W lineaments. They are represented by syenitic rock-types (silica undersaturated to slightly silica oversaturated) potassic rocks and are associated to stockworks of carbonatitic veins, dykes and so on. Geochemical characteristics and isotope systematics point to a veined mantle source particularly enriched in LILE and LREE. The carbonatitic veins show high contents of Ba, Sr, Th and REE and are suitable as potential ore deposits.

Crystal Chemistry and Geochronology of Thorium-Rich Monazite from Kovela Granitic Complex, Southern Finland  [PDF]
Thair Al-Ani, Pentti H?ltt?, Sari Gr?nholm, Lassi Pakkanen, Nadhir Al-Ansari
Natural Resources (NR) , 2019, DOI: 10.4236/nr.2019.106016
Abstract: Abundant porphyritic granites, including Grt-bearing and Bt-bearing porphyritic granites, and porphyritic potash-feldspar granite (trondhjemite-granitic composition) are widely distributed within the Kovela granitic complex Southern Finland, which associated with monazite-bearing dikes (strong trondhjemite composition). The investigated monazite-bearing dikes are dominated by a quartz + K-feldspar + plagioclase + biotite + garnet + monazite assemblage. The monazite forms complexly zoned subhedral to euhedral crystals variable in size (100 - 1500 μm in diameter) characterized by high Th content. The chemical zoning characterised as: 1) concentric, 2) patchy, and 3) intergrowth-like. Textural evidence suggests that these accessory minerals crystallized at an early magmatic stage, as they are commonly associated with clusters of the observed variations in their chemical composition are largely explained by the huttonite exchange \"\", and subordinately by the cheralite exchange \"\" with proportions of huttonite (ThSiO4) and cheralite [CaTh(PO4)2] up to 20.4% and 9.8%, respectively. Textural evidence suggests that these monazites and associated Th-rich minerals (huttonite/thorite) crystallized at an early magmatic stage, rather than metamorphic origin. The total lanthanide and actinide contents in monazite and host dikes are strongly correlated. Mineral compositions applied to calculate P-T crystallization conditions using different approaches reveal a temperature range of 700
Petrology and monazite dating of the Fe-rich gneisses from Kokava (Veporic Unit, Western Carpathians, Slovakia): Devonian sediments supplied from Gondwanan-sources metamorphosed in the Variscan times
Kone?ny P,Kohút M,Rojkovi? I,Siman P
Journal of Geosciences , 2011, DOI: 10.3190/jgeosci.094
Abstract: The Fe-rich gneisses from vicinity of Kokava nad Rimavicou (Central Slovakia) were studied by electron microprobe to resolve the origin of the iron ore bodies. Whole-rock chemistry of the ironstones shows the lack of CaO, MgO and partly elevated P2O5 contents. This, together with the mineral assemblage of almandine + magnetite + grunerite + ilmenite + quartz + apatite + allanite + zircon + monazite suggests an origin by metamorphism of sedimentary protolith and disproves the older idea about the formation as a skarn. The Fe-Ti oxides thermometry suggests temperatures of 360-420 °C, and the average oxygen fugacity of Δlog fO2 normalized to the FMαQ is +0.13. The reconstructed oxygen fugacity for temperatures 500-600 °C (amphibolite facies) yields an interval of c. +1 to +3 Δ log fO2 (FMαQ). The presence of detrital zircons, and monazites dated in this study, reveals a participation of lithologies of the pan-African orogen. The source rocks of the Devonian ironstones sedimented probably as oolitic chamosite in lagoons. The dated detrital monazites cores (612-400 Ma) show an affinity to source rocks formed in northern peri-Gondwana due to rifting and opening of the Rheic Ocean and separation of Avalonia and Armorica microcontinents. The majority of monazite data from the rims of detrital grains and from unzoned metamorphic grains bear an evidence of Meso-Variscan metamorphism with ages clustering between 360 and 320 Ma (342 ± 4Ma - weighted mean ± 2σ). The younger population with elevated Th contents (18.0-20.5 wt. %) giving the ages of 310-240 Ma (279 ± 2 Ma - weighted mean) is connected with the collapse of Variscan orogen and/or the onset of the early Alpine continental rifting. The Alpine ages are very rare, but a few monazites and one Th-U-Si inclusion in quartz yielded Cretaceous ages (115-85 Ma).
Evolution of the Early Permian volcanic-plutonic complex in the western part of the Permian Gobi-Altay Rift (Khar Argalant Mts., SW Mongolia)  [PDF]
Buriánek D,Han?l P,Budil P,Gerdes A
Journal of Geosciences , 2012, DOI: 10.3190/jgeosci.116
Abstract: The Lower Permian volcano-sedimentary complexes of the Khar Argalant and Delger Khangay formations in the Khar Argalant Mts. in south-western Mongolia are products of postorogenic within-plate magmatic activity. They consist of terrestrial lavas and pyroclastic flows with local intercalations of clastic sedimentary rocks. Vascular plants in volcano-clastic layers correspond to typical Lower to Middle Permian terrestrial associations formed under dry to intermediate conditions of temperate to colder climatic zones. The plant communities of all three formations show affinities to the Siberia (Angara) “Cordaitean taiga”. Relationships of volcanic rocks suggest simultaneous eruptions of mafic (basalt to trachyandesite) and felsic (trachyte to rhyolite) lavas. The rocks of both formations have similar major- and trace-element contents as well as volcanological character. The granite of the Shar Oroy Massif, with zircon concordia age of 285 ± 1 Ma, was roughly contemporaneous with the volcanic rocks of the Delger Khangay Fm. The Early/Late Permian clastic sedimentary rocks of the Butnaa Khudag Fm. in the hanging wall of the Delger Khangay Fm. postdated the terrestrial volcanic events. Geochemical and structural characteristics suggest that the Shar Oroy Massif and the surrounding Permian volcanic suite represent an eroded, shallow-level plutonic centre and its eruptive cover, which evolved during a crustal extension.
Zircon to monazite phase transition in CeVO4  [PDF]
V. Panchal,S. Lopez-Moreno,D. Santamaria-Perez,D. Errandonea,F. J. Manjon,P. Rodriguez-Hernandez,A. Munoz,S. N. Achary,A. K. Tyagi
Physics , 2011, DOI: 10.1103/PhysRevB.84.024111
Abstract: X-ray diffraction and Raman-scattering measurements on cerium vanadate have been performed up to 12 and 16 GPa, respectively. Experiments reveal that at 5.3 GPa the onset of a pressure-induced irreversible phase transition from the zircon to the monazite structure. Beyond this pressure, diffraction peaks and Raman-active modes of the monazite phase are measured. The zircon to monazite transition in CeVO4 is distinctive among the other rare-earth orthovanadates. We also observed softening of external translational Eg and internal B2g bending modes. We attributed it to mechanical instabilities of zircon phase against the pressure-induced distortion. We additionally report lattice-dynamical and total-energy calculations which are in agreement with the experimental results. Finally, the effect of non-hydrostatic stresses on the structural sequence is studied and the equations of state of different phases are reported.
Monazite Breakdown in Metapelites From Wedel Jarlsberg Land, Svalbard — Preliminary Report
Jarostaw Majka , Bartosz Budzyń
Mineralogia , 2006, DOI: 10.2478/v10002-007-0006-9
Abstract: Metapelites from the SW part of Wedel Jarlsberg Land were progressively metamorphosed under amphibolite facies conditions followed by a Caledonian low-temperature metamorphic event under greenschist facies conditions. The latter resulted in various stages of monazite breakdown. These include monazite alterations and the formation of allanite-apatite coronas.
Comparison of SHRIMP U-Pb dating of monazite and zircon
Yusheng Wan,Dunyi Liu,Ping Jian
Chinese Science Bulletin , 2004, DOI: 10.1360/03wd0638
Abstract: Monazite dating is an important technique in geochronological studies. However, monazite U-Pb dating by SHRIMP is much less popular than zircon in geochronological applications. This paper compares the results of SHRIMP U-Pb dating of monazites and zircons separated from two granite samples, indicating that monazite SHRIMP U-Pb dating at the Beijing SHRIMP Centre is feasible and provides identical results within error.
Multiple monazite growth in the reskutan migmatite: evidence for a polymetamorphic Late Ordovician to Late Silurian evolution in the Seve Nappe Complex of west-central J mtland, Sweden  [PDF]
Majka J,Be’eri-Shlevin Y,Gee D G,Ladenberger A
Journal of Geosciences , 2012, DOI: 10.3190/jgeosci.112
Abstract: Monazite from granulite-facies rocks of the reskutan Nappe in the Scandinavian Caledonides (Seve Nappe Complex, Sweden) was dated using in-situ U-Th-total Pb chemical geochronology (CHIME). Multi-spot analyses of a non-sheared migmatite neosome yielded an age of 439 ± 3 Ma, whereas a sheared migmatite gave 433 ± 3 Ma (2σ). Although the obtained dates are rather similar, a continuous array of single dates from c. 400 Ma to c. 500 Ma suggests possibly a more complex monazite age pattern in the studied rocks. The grouping and recalculation of the obtained results in respect to Y-Th-U systematics and microtextural context allowed distinguishing several different populations of monazite grains/growth zones. In the migmatite neosome, low-Th and low-Y domains dated at 455 ± 11 Ma are considered to have grown under high-grade sub-solidus conditions, most likely during a progressive burial metamorphic event. The monazites with higher Th and lower Y yielded an age of 439 ± 4 Ma marking the subsequent partial melting event caused by decompression. The youngest (423 ± 13 Ma) Y-enriched monazite reveals features of fluid-assisted growth and is interpreted to date the emplacement of the reskutan onto the Lower Seve Nappe. In the sheared migmatite, the high-Th and low-U (high Th/U) monazite with variable Y contents yielded an age of 438 ± 4 Ma, which is interpreted to date the partial melting event. Relatively U-rich rims on some of the monazite grains again reveal features of fluid-assisted growth, and thus their age of 424 ± 6 Ma is interpreted as timing the nappes emplacement. These results call, however, for further more precise, isotopic (preferably ion microprobe) dating of monazite in the studied rocks.
In Situ LA-MC-ICP-MS U-Pb Isotopic Dating of Monazite
LA-MC-ICP-MS独居石微区原位U-Pb同位素年龄测定

CUI Yu-rong,ZHOU Hong-ying,GENG Jian-zhen,LI Huai-kun,LI Hui-min,
崔玉荣
,周红英,耿建珍,李怀坤,李惠民

地球学报 , 2012,
Abstract: Characterized by rich U, Th and low initial Pb content, monazite is an ideal object for U-Pb and Th-Pb isotopic dating. Due to the existence of monazite in a variety of rocks, the U-Th-Pb dating of monazite has a broad application prospect. A new method is reported in this paper. The monazite samples were analyzed by using 193 nm ArF excimer laser ablation system coupled with NEPUNE multi-collector inductively coupled plasma mass spectrometer. The monazite samples AL01, BL02 and CL03 were dated by this method. The weighted average 206Pb/238U ages of AL01 and BL02 were (288.3±1.1) Ma (n=19) and (446.8±2.3) Ma (n=41) respectively, and the isochron age of CL03 was (396.8±8.8) Ma (n=55), showing satisfactory results.
Monazite breakdown in metapelites from Wedel Jarlsberg Land, Svalbard — preliminary report  [PDF]
Jaros?aw Majka,Bartosz Budzyń
Mineralogia Polonica , 2006,
Abstract: Metapelites from the SWpart ofWedel Jarlsberg Land were progressively metamorphosedunder amphibolite facies conditions followed by a Caledonian low-temperature metamorphic event undergreenschist facies conditions. The latter resulted in various stages of monazite breakdown. These includemonazite alterations and the formation of allanite-apatite coronas.
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