Validity of the Apatite/Merrillite Relationship in Evaluating the Water Content in the Martian Mantle: Implications from Shergottite Northwest Africa (NWA) 2975
| Autor: | Richard Wirth, Ewa Słaby, Hans-Jürgen Förster, Łukasz Birski, Izabela Moszumańska, Alicja Wudarska |
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| Rok vydání: | 2017 |
| Předmět: |
010504 meteorology & atmospheric sciences
Rare earth Geochemistry Electron microprobe 010502 geochemistry & geophysics 01 natural sciences ferromerrillite Apatite Mantle (geology) law.invention law Crystallization LA-ICP-MS Water content 0105 earth and related environmental sciences Martian Fluorapatite lcsh:QE1-996.5 fluorapatite chlorapatite volatiles shergottite TEM EPMA lcsh:Geology visual_art visual_art.visual_art_medium General Earth and Planetary Sciences Geology |
| Zdroj: | Geosciences Geosciences, Vol 7, Iss 4, p 99 (2017) Geosciences; Volume 7; Issue 4; Pages: 99 |
| Popis: | Phosphates from the Martian shergottite NWA 2975 were used to obtain insights into the source and subsequence differentiation of the melt/melts. The crystallization of two generations of fluorapatite (F > Cl~OH and F-rich), chlorapatite and ferromerrillite-merrillite were reconstructed from TEM (Transmission Electron Microscopy) and geochemical analyses. The research results indicated that the recognized volatiles budget of the two generations of fluorapatite was related to their magmatic origin. The apatite crystals crystallized from an evolved magma during its final differentiation and degassing stage. In turn, chlorapatite replaced ferromerrillite-merrillite and was not related to, mantle-derived shergottite magma. The relationship between merrillite and apatite indicates that apatite is most probably a product of merrillite reacting with fluids. REE (rare earth elements) pattern of Cl-apatite might point to an origin associated with exogenous fluids mixed with fluids exsolved from evolved magma. The study shows that, among the three types of apatite, only the fluorapatite (F > Cl~OH) is a reliable source for assessing the degree of Martian mantle hydration. The occurrence of apatite with merrillite requires detailed recognition of their relationship. Consequently, the automatic use of apatite to assess the water content of the magma source can lead to false assumptions if the origin of the apatite is not precisely determined. |
| Databáze: | OpenAIRE |
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