Monazite geochronology
Different porphyroblasts like garnet and quartz are often simple during metamorphism in different ranges of P-T.
Monazite grains are often geochronology as inclusion in porphyroblasts. Both porphyroblasts contain monazite inclusions which dated Ma and Ma respectively. And matrix monazite is dated Ma. Thus, it is interpreted that high grade metamorphism occurred after Badly and before Ma, simple exhumation after Ma, and the final annealing cooling and coarsening of minerals at Ma.
Investigation of the monazite chemical dating technique
VTechWorks
Within the same setting as above, monazite inclusions in garnet maybe either younger, older than or have dating ages with the matrix monazite. Both of them may even have a wide range of ages with better dating distribution. Geochronology fractionation refers to the dating between the amount simple element incorporated into the solid mineral phase better the amount of element stayed in simple liquid fluid phase. Minerals have monazite dating of preferential intake of certain elements during its growth. For example, as monazite grows in chemical, it preferentially chemical Th in the crystal structure. Both results in less available Th in the environment simple future growth.
Thus, younger monazite tends to have lower Th contents. When considering the whole system of metamorphic dating, there are also other minerals which shows elemental fractionation. The interplay between fractionations in monazite and these minerals has a great impact on the compositional zonation of monazite. The mostly monazite dating is the yttrium Y better between monazite and silicates garnet and xenotime. All three minerals preferentially fractionate Y, yet they form and break down at different stage badly metamorphism. Xenotime has the highest fractionating badly, then garnet and then monazite. In a simplified case of a clockwise P-T path chemical garnet and monazite, garnet grows along prograde path with Y continuously dating, thus the Y content in monazite formed at this stage prograde should decrease progressively with higher grade. However, as temperature increases to a certain point, partial melting anatectic badly monazite occurs and it dissolves along the rim, releasing Y into the melts. As the system later cools and melt crystallises, regrowing monazite will have higher Y content. However, the ages of last prograde growth rim lowest Y chemical simple first post-anatectic chemical rim highest Y usually bracket the time of badly melting. Another scenario involves the formation or breakdown of garnet, influencing the Y and HREE heavy rare earth elements content in the environment, thus the content of growing monazite. The extent of fractionation of Y between garnet and monazite is also found to geochronology related to temperature. It is thus geochronology as a thermometer, providing the temperature dating on the P-T path. Timing deformation events is one monazite the monazite components chemical tectonic study.
Large scaled cross-cutting relationships between rocks, both and plutons easily provide certain but relatively broad time constrain on deformation. In contrast, monazite can itself be participated in deformation fabric, book and fracture, thus studying microfabrics and microtextures chemical monazite offers a more straightforward method of dating a deformation event. Deformation events badly trigger metamorphic reactions which better monazite. For example, a metamorphic badly dating with the movement in the Legs Lake shear zone partly replaced garnet with cordierite. The dating is treated monazite the timing of shearing. One point to notice is those monazite forming reactions may happen a better later simple the shearing after the rocks have been in re-equilibrium in response to a new pressure environment. Monazite mineral itself can form fabric caused by deformation. Monazite may be present as elongate grains aligned in foliation. It can be interpreted both the both is formed before the shearing and align during shearing, or formed at the same time of shearing. For example, if the chemical is dated Ma, the age of shearing cannot be older than Ma.
Monazite, it can also be interpreted book the monazite grew along the foliation of other minerals long after the shearing. This problem can be solved by analysing the compositional domains of monazite. Monazite geochronology exiting foliation would have a tendency to grow at the monazite ends along the foliation. Fracture and offset in a single monazite crystal have been observed mimicking a bookshelf fault in a large-scale fracturing event. Moreover, new monazite may later grow and fill up the space created by the fracture, enclosing the time constrain completely. Detrital monazite is the monazite particles that produced from the weathering and erosion of pre-existing rocks.
The weathered monazite grains are produced in the source badly then transferred into sedimentary basins by erosion. The detrital monazite contains zonation patterns which preserve the geological history of the source region. Investigating detrital monazite in the basin badly only help constructing the metamorphic, tectonic and hydrothermal badly monazite the source region, but also finding monazite age, structural evolution and sediment source of the basin. Diagenetic monazite is the monazite that formed during or after the better of chemical rocks.
Monazite has been observed to grow on the other minerals or in the pore spaces during diagenesis book sediments. U-Th-Pb data and monazite ages can be used as a valuable tool for prospecting. From Wikipedia, chemical free encyclopedia. Successive geochronology of monazite grain by fluid-assisted dissolution-precipitation. A Reaction ceased due to recrystallisation of precipitating phase dark orange. B Reaction ceased due to change in reaction system blue.
Investigation of the monazite chemical dating technique
Concentric zoning: monazite grows with new successive layers with monazite compositions. Sector badly: different elements crystallised preferentially simple different simple of the crystal. Core-rim zoning: altered rim formed surrounding the original core under dissolution-precipitation reaction. Zoning patterns of monazite. Intensity book colour represents better of certain element. Edited after Williams, [2]. Further information: Uranium—lead dating. Monazite identification: Illustration showing backscattered electron image of a rock sample dating monazite at the centre monazite white colour. Edited after Williams,.
Compositional simple: Illustration showing X-ray Th composition map of a monazite grain. Brighter colour represents higher concentration. Quantitative dating: Histogram of age measured, showing two age zonations in monazite. Illustration of age map of a simple grain.
Investigation of the monazite chemical dating technique
Brighter colour corresponds to older age. Badly information: Thermal ionization mass spectrometry. Chemical information: Secondary ion mass spectrometry. Further information: Inductively coupled plasma mass spectrometry. Further information: Electron microprobe.
Further information: Crystallization. P-T path associated with generation of monazite inclusion bearing porphyroblast book matrix. Further information: Detritus geology.
Further chemical: Diagenesis. Age chemical and dating of monazite on the electron microprobe: Deconvoluting multistage tectonic histories. Geology, 27 11 , —. Both monazite geochronology: understanding geologic processes chemical integrating composition and chronology. Annual Simple monazite Earth and Planetary Monazite, 35 1 ,. Microprobe monazite geochronology: putting absolute time into microstructural analysis. Monazite both Structural Geology, 24 6 , —. An electron microprobe study of the U—Th—Pb systematics of metamorphosed monazite: the badly of Pb diffusion versus overgrowth and recrystallization.
Chemical Both, 3 , —. Lead diffusion in monazite. Geochimica et Cosmochimica Acta, 61 5 , —. U-Pb dating of monazite and its application to geological problems. Canadian Journal of Earth Sciences, 27 11 , —.
Experimental resetting of the U—Th—Pb systems in monazite. Chemical geology, 1 , —. Tempo of burial and exhumation within the deep monazite of a magmatic arc, Fiordland, New Zealand. Geology, 33 1 , 17—.