Mixed Materials
K-feldspar hygrochronology
| Τίτλος: | K-feldspar hygrochronology |
|---|---|
| Συγγραφείς: | Villa, I, Hanchar, J, VILLA, IGOR MARIA, Hanchar, JM |
| Στοιχεία εκδότη: | Elsevier country:US 2013 |
| Τύπος εγγράφου: | Mixed materials |
| Περίληψη: | The significance of the multi-isotopic record preserved in K-feldspars is assessed on samples from the Aar metagranite, Central Alps, Switzerland having very tight independent geological constraints. Stepwise leaching reveals that two diachronically grown K-feldspar generations coexist: Kfs-1 (>= 35 Ma old, Ca-poor, Rb-Cl-rich, with low Sr-87/Sr-86 and high Pb-206/Pb-204) and Kfs-2 (<= 10 Ma old, antithetic isotopic signatures deriving from external fluids). Microtextures imaged by cathodoluminescence, backscattered electrons, and electron probe microanalysis are patchy and chemically heterogeneous, with pronounced enrichments in Ba in the retrogressed regions. This confirms the simultaneous presence of fluid-dominated retrogression and recrystallization and isotopic inheritance. The staircase-shaped Ar-40/Ar-39 age spectrum correlates with the Ca/K and Cl/K signatures. This reflects a mixture of heterochemical K-feldspar generations, and not an intracrystalline Ar gradient caused by diffusion. The shape of the age spectrum and the in vacuo release kinetics proceed from entirely different physical and geological phenomena. What K-feldspars can be effectively used for is to constrain the timing of the fluids that interacted with them by multi-isotopic analyses, rather than to model a "cooling history" from Ar-39 release alone. The identification of multiple mineral generations by imaging combined with multi-isotopic analysis enables the accurate dating of the events of a multistage evolution after the initial crystallization of the rock in which the minerals occur. |
| Όροι ευρετηρίου: | systematic analysi, alkali feldspar, swiss alp, geochronology, isotope, ar39-ar40, Settore GEOS-01/C - Geochimica e vulcanologia, info:eu-repo/semantics/article |
| Σύνδεσμος: | info:eu-repo/semantics/altIdentifier/wos/WOS:000312854900003 volume:101 firstpage:24 lastpage:33 numberofpages:10 journal:GEOCHIMICA ET COSMOCHIMICA ACTA |
| Διαθεσιμότητα: | Open access content. Open access content |
| Σημείωση: | STAMPA English |
| Other Numbers: | ITBAO oai:boa.unimib.it:10281/45140 10.1016/j.gca.2012.09.047 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84869396670 1308905507 |
| Πηγή συνεισφοράς: | BICOCCA OPEN ARCH From OAIster®, provided by the OCLC Cooperative. |
| Αριθμός Καταχώρησης: | edsoai.on1308905507 |
| Βάση Δεδομένων: | OAIster |
| Η περιγραφή δεν είναι διαθέσιμη |