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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-skinned style of deformation is typical of many fold and thrust belts developed in the foreland of a collisional zone or back arc of a continental volcanic arc. This is particularly the case where a good basal decollement exists, usually in a weaker layer like a shale , evaporite , or a zone of high pore fluid pressure. [ 2 ]
Undulose extinction or undulatory extinction is a geological term referring to the type of extinction that occurs in certain minerals when examined in thin section under cross polarized light. As the microscope stage is rotated, individual mineral grains appear black when the polarization due to the mineral prevents any light from passing through.
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a thin slice of a rock or mineral sample, prepared in a laboratory, for use with a polarizing petrographic microscope, electron microscope and electron microprobe. A thin sliver of rock is cut from the sample with a diamond saw and ground
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.
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 ]
In such cases, a thin section of the mineral is used and examined under polarized transmitted light with a petrographic microscope. Another device using this property to identify minerals is the dichroscope .