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Monazite is an important ore for thorium, [8] lanthanum, and cerium. [9] It is often found in placer deposits. India, Madagascar, and South Africa have large deposits of monazite sands. The deposits in India are particularly rich in monazite. Monazite is radioactive due to the presence of thorium and
Monazite can form in fabrics caused by deformation. Monazite may be present as elongate grains aligned in foliation. It can be interpreted that either the monazite formed before the shearing and was aligned during shearing, or formed at the same time as the shearing. [3] It thus provides an upper limit of the shearing age.
The thin section has been slightly rotated to show the characteristic change in color of the tourmaline known as pleochroism. Figure 5c. Cross-polarized light photomicrograph of tourmaline in sample CV-114 from the Strathbogie Granite
In the study of metamorphic petrology, uranium–thorium–lead dating of monazite (monazite geochronology) is an effective method to determine the P-T history. [ 29 ] [ 30 ] Monazite is a phosphate mineral containing light rare-earth-elements (LREE) that occurs in a wide range of rock types. [ 31 ]
Monazite-(Sm) is an exceedingly rare representative of the monazite group, with samarium being the dominant rare earth element in its structure. It is the samarium analogue of monazite-(Ce), monazite-(La), and monazite-(Nd). It is only the second known mineral with samarium being the mineral-forming element, after florencite-(Sm). [3]
It is the cerium-dominant analogue of monazite-(La), monazite-(Nd), and monazite-(Sm). It is also the phosphorus analogue of gasparite-(Ce). [ 3 ] The group contains simple rare earth phosphate minerals with the general formula of AXO 4 , where A = Ce, La, Nd, or Sm (or, rarely, Bi), and X = P or, rarely, As.
QAPF diagram for classification of intrusive igneous rocks, with the monzonite field highlighted Photomicrograph of thin section of monzonite (in cross polarised light) Photomicrograph of thin section of monzonite (in plane polarised light) The Notch Peak monzonite intrusion in Utah inter-fingers (partly as a dike) with highly metamorphosed Cambrian carbonate host rocks
It is also known to occur as small grains in detrital sands. Crystals are rare, but when found can produce nicely shaped short prismatic crystals with pyramidal terminations. It is commonly associated with zircon, monazite, gadolinite, fergusonite, uraninite, yttrialite and pyrochlore. [4] Thorite is currently an important ore of uranium.