U-Th-Pb monazite dating by EPMA

Skip to main content. Log In Sign Up. Two Madagascar monazite crystals as potential reference materials for U-Pb microanalysis. Monazite TS-Mnz is reddish brown with initial weight of

Skip to main content. Log In Sign Up. Two Madagascar monazite crystals as potential reference materials for U-Pb microanalysis. Monazite TS-Mnz is reddish brown with initial weight of The TS-Mnz in high-contrast BSE-imaging demonstrates homogeneous, clear domains, and domains including numerous inclusions.

The TS-Mnz contains 4. Monazite ANK-Mnz is significantly larger, with an initial weight of g. The crystal reveals gem quality, crystal-clear domains up to several hundred microns-sizedhomogeneous in high contrast BSE-imaging; and domains with inclusions. The rim is porous, easy to be recognized and neglected for the standard. The ANK-Mnz contains 5. Monazite in nature is compositionally heterogeneous and commonly registers multiple geological processes that occasionally may affect its Th-U-Pb system.

Consequently, natural monazite is a difficult material for age standard. Our preliminary results demonstrate that the selected monazite crystals, despite their compositional variations, reveal homogeneous concordant ages and may be considered as new potential age reference materials for U-Pb age microanalysis.

Electron microprobe dating of monazite substantiates ages of major geological events in the southern Brazilian shield. Developing an inverted Barrovian sequence; insights from monazite Dating seiten fur 20 jahrige hochzeit. Geometry, kinematics and thermal structure. Syn-deformation fluid-assisted growth of monazite during renewed high-grade metamorphism in metapelites of the Central Rhodope Bulgaria, Greece.

Three domains are distinguished in the monazite grains: The age and chemical zonation of the monazites attest to the reservation of primary monazite in the xenolith despite the interaction with the andesite lava. Thorium concentrations of 2 to 9 wt.

In the Himalayan region of Sikkim, the well-developed inverted metamorphic sequence of the Main Central Thrust MCT zone is folded, thus exposing several transects through the structure that reached similar metamorphic grades at In the Himalayan region of Sikkim, the well-developed inverted metamorphic sequence of the Main Central Thrust MCT zone is folded, thus exposing several transects through the structure that reached similar metamorphic grades at different times.

In-situ LA-ICP-MS U—Th—Pb monazite ages, linked to pressure—temperature conditions via trace-element reaction fingerprints, allow key aspects of the evolution of the thrust zone to be understood for the first time. The ages show that peak metamorphic conditions were reached earliest in the structurally highest part of the inverted metamorphic sequence, Advice for men on dating Bavarian women Life in Munich Toytown Germany the Greater Himalayan Sequence GHS in the hanging wall of the MCT.

These processes appear to have occurred several times during the prolonged ductile evolution of the thrust. The petrochronologic methods applied here constrain a complex temporal and thermal deformation history, and demonstrate that inverted metamorphic sequences can preserve a rich record of the duration of progressive ductile thrusting.

Samples from both locations Samples from both locations have experienced two stages of high temperature U-Th-Pb monazite dating by EPMA during Alpine U-Th-Pb monazite dating by EPMA.

The first event involved mid-Mesozoic granulite facies dehydratation melting. The second event involved mid-Cenozoic lower-grade fluid-assisted partial melting. The latter is well expressed in adjacent felsic rocks but had limited impact on the Grt-Ky metapelites.

Most samples display evidence for strong ductile shearing in the presence of fluids. Monazite is present U-Th-Pb monazite dating by EPMA the highly U-Th-Pb monazite dating by EPMA matrix and as inclusions in garnet and kyanite. Unlike the inclusions, matrix monazites display features of fluid-assisted dissolution-recrystallization.

Y-poor domains with U-Th-Pb ages of between ca. Y-rich domains with mid-Cenozoic ages occur as rims, or as small satellite grains surrounding the Mesozoic grains.

The U-Th-Pb monazite dating by EPMA monazite domains crystallized at the expense of the Mesozoic ones and simultaneously incorporated Y provided by the fluid-assisted resorption of garnet.

An age of ca. Similar ages exist for the crystallization of leucosomes and pegmatites in the adjacent migmatitic gneisses, indicating that the fluids responsible for the precipitation of the Cenozoic monazites were U-Th-Pb monazite dating by EPMA released during the crystallization of nearby anatectic melts.

Together with associated rutile and biotite, many newly grown monazites show a preferred orientation U-Th-Pb monazite dating by EPMA the matrix foliation.

This supports the hypothesis of dynamic dissolution-precipitation as an efficient mean to promote renewed monazite crystallization during ductile deformation of the host rock at ca. The occurrence of U-Th-Pb monazite dating by EPMA Tonian—Cryogenian Ma regional metamorphic event in Central Madagascar and the geodynamic setting of the Imorona—Itsindro Ma magmatic suite.

Fluid-induced disturbance of the U-Th-Pb chronometers in monazite: Disturbance versus preservation of U—Th—Pb ages in monazite during fluid—rock interaction: Monazite is extensively used to date crustal processes and is usually considered to be resistant to diffusive Pb loss.

Nevertheless, fluid-assisted recrystallisation is known to be capable of resetting the monazite chronometer. This study focuses on chemical and isotopic disturbances in monazite grains from two microgranite intrusions in the French Central Massif Charron and Montasset. Petrologic data and oxygen isotopes suggest that both intrusions have interacted with alkali-bearing hydrothermal-magmatic fluids. In the Charron intrusion, regardless of their textural location, monazite grains are sub-euhedral and cover a large domain of compositions.

The Montasset intrusion was later affected by an additional F-rich crustal fluid with crystallisation U-Th-Pb monazite dating by EPMA Ca-REE-fluorocarbonates, fluorite, calcite and chloritisation. By contrast, groundmass monazite shows dissolution-recrystallisation features associated with apatite and thorite precipitation Th-silicate and strong chemical reequilibration.

These results show that F-rich fluids are responsible for Th mobility and incorporation of excess Pb, which thus strongly disturbed the U—Th—Pb chronometers in the monazite. Chemical U— Th — Pb dating of monazite from 12 schists throughout western and central Tasmania define a peak metamorphic age of ca Ma.

This age is very close to the age of arc — continent collision and ophiolite emplacement, implying This age is very close to the age of arc — continent collision and ophiolite emplacement, implying very rapid uplift and cooling. To the U-Th-Pb monazite dating by EPMA, along the western margin of the South Tasman Rise, metamorphism U-Th-Pb monazite dating by EPMA later at Ma, which correlates with a late stage of the Ross Orogeny, Antarctica.

However, the Tyennan Orogeny only produced metamorphic rocks during the early stage associated with ophiolite obduction at — Ma.

The intense compressional event recognised in the Delamerian and Ross Orogeny at — Ma is correlated with a mild basin inversion in Tasmania, and no metamorphism on mainland Tasmania has been recognised associated with this event. The westernmargin of the South Tasman Rise is a fragment of the Ross Orogen and does not correlate directly with Tasmania.

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