Εξειδίκευση τύπου :	Άρθρο σε επιστημονικό περιοδικό
Τίτλος:	Octahedral cation distribution in palygorskite
Δημιουργός/Συγγραφέας:	[EL] Χρυσικός, Γεώργιος Δ.[EN] Chryssikos, Georgios D. [EL] Γκιώνης, Βασίλης[EN] Gionis, Vassilis Kacandes, George H. Stathopoulou, Elizabeth T. Suarez, Mercedes Garcia-Romero, Emilia del Rio, Manuel Sanchez
Εκδότης:	Mineralogical Society of America
Τόπος έκδοσης:	CHANTILLY
Ημερομηνία:	2009-01
Γλώσσα:	Αγγλικά
ISSN:	0003-004X
DOI:	10.2138/am.2009.3063
Περίληψη:	The OH speciation of 18 palygorskite samples from various localities were evaluated by near infrared spectroscopy (NIR) and compared to the corresponding octahedral composition derived from independent, single-particle analytical electron microscopy (AEM). NIR gives evidence for dioctahedral-like (AlAlOH, AlFe(3+)OH, Fe(3+)Fe(3+)OH) and trioctahedral-like (Mg(3)OH) species. Therefore, palygorskite can be approximated by the formula yMg(5) Si(8)O(20)(OH)(2).(1 - y)[xMg(2)Fe(2).(1-x)Mg(2)Al(2)] Si(8)O(20)(OH)(2), where x is the Fe content of the dioctahedral component, and y is the trioctahedral fraction. The values of x estimated from the NIR data are in excellent agreement with the Fe/((VI)Al + Fe) ratio from AEM (R(2) = 0.98, sigma = 0.03), thus suggesting that all octahedral Al and Fe in palygorskite participate in M2M2OH (dioctahedral-like) arrangements. furthermore, y values from AEM can be compared to NIR (R(2) = 0.90 and sigma = 0.05) after calibrating the relative intensity of the Mg(3)OH vs. (Al,Fe)(2)OH overtone bands using AEM data. The agreement between the spectroscopic and analytical data are excellent. The data show that Fe(3+) for Al substitution varies continuously in the analyzed samples over a broad range (0 <x < 0.7), suggesting that fully ferric dioctahedral palygorskites (x = 1) may exist. On the other hand, the observed upper trioctahedral limit of y= 0.50 calls for the detailed structural comparison of Mg-rich palygorskite with sepiolite.
Τίτλος πηγής δημοσίευσης:	American Mineralogist
Τόμος/Κεφάλαιο:	94
Τεύχος:	1
Σελίδες:	200-203
Θεματική Κατηγορία:	[EL] Γεωλογία[EN] Geology
Λέξεις-Κλειδιά:	Palygorskite Fe-rich Mg-rich structure near infrared spectroscopy trioctahedral dioctahedral composition AEM sepiolite Geochemistry & Geophysics Mineralogy
Αξιολόγηση από ομότιμους (peer reviewed):	Ναι
Κάτοχος πνευματικών δικαιωμάτων:	© MINERALOGICAL SOC AMER
Ηλεκτρονική διεύθυνση περιοδικού (link) :	http://www.minsocam.org/MSA/AmMin/AmMineral.html
Εμφανίζεται στις συλλογές:	Ινστιτούτο Θεωρητικής και Φυσικής Χημείας (ΙΘΦΧ) - Επιστημονικό έργο