The Fe-Mn phosphate associations from the Pinilla de Fermoselle pegmatite, Zamora, Spain: occurrence of kryzhanovskite and natrodufrénite
Robles, Encarnación Roda; Fontan, François; Pesquera Pérez, Alfonso; Keller, Paul
European Journal of Mineralogy Volume 10 Number 1 (1998), p. 155 - 168
published: Jan 26, 1998
manuscript accepted: Sep 29, 1997
manuscript received: Nov 7, 1996
ArtNo. ESP147051001015, Price: 29.00 €
Abstract Complex associations of Fe-Mn phosphates occur in a Li-bearing pegmatite of the Pinilla de Fermoselle area (Zamora, Spain). This pegmatite shows internal zoning, evolving from a barren composition along the contact with granitic rocks to a Li-rich zone along the contact with hornfels. The Fe-Mn phosphates occur as nodular masses in the intermediate zone. Ferrisicklerite is the first mineral of the sequences, but the presence of initial triphylite can not be excluded. Heterosite, kryzhanovskite, alluaudite, natrodufrénite, barbosalite, huréaulite, lipscombite, jahnsite and rockbridgeite are of hydrothermal origin, while leucophosphite, phosphosiderite and mitridatite are the main supergenic phosphates. Two different phosphate associations can be distinguished, on the basis of their typical mineral assemblages. Association I is characterized by the presence of abundant alluaudite and kryzhanovskite. In association II, natrodufrénite occurs together with abundant huréaulite, barbosalite, and lipscombite. The Fe/(Fe+Mn) ratios for ferrisicklerite, heterosite and alluaudite in association I are only slightly, but systematically lower than in association II. The appearance of kryzhanovskite and natrodufrénite, and the absence of triphylite are the most interesting features of the phosphate associations of this pegmatite. The formation of phosphate minerals such as heterosite, alluaudite and huréaulite can be compared with evolutionary steps in pegmatites from other pegmatite fields.