PHOSPHATE MINERALOGY AND PARAGENESIS OF THE PALERMO #2 PEGMATITE, NORTH GROTON, NEW HAMPSHIRE

The Palermo #2 pegmatite in North Groton, New Hampshire is located in the Grafton pegmatite field of west-central New Hampshire. It is a rare-element pegmatite of the beryl-phosphate subtype which hosts a number of primary and secondary phosphate species. The primary phosphates triphylite, fluorapatite, hydroxylapatite and montebrasite occur mainly in the core margin. Late-stage, carbonate-bearing aqueous fluids have metasomatically altered these primary phosphates producing a diverse suite of nearly 40 species of secondary phosphate minerals and associated carbonates. Secondary phases related to the alteration of triphylite include: ferrisickerlite, heterosite, wolfeite, rockbridgeite, beraunite, laueite, strunzite, vivianite, ludlamite, kryzhanovskite, jahnsite-(CaMnFe), jahnsite-(CaMnMn), stewartite, ushkovite, whitmoreite, childrenite, eosphorite, gormanite, messelite, fairfieldite, mitridatite, strengite and phosphosiderite. Secondary phases related to the alteration of montebrasite ± hydroxylapatite/fluorapatite include: scorzalite, lazulite, paravauxite, gordonite, gormanite, souzalite, augelite, chlorapatite, whiteite-(MnFeMg), whiteite-(CaMnMg), jahnsite-(CaMnFe), jahnsite-(CaMnMn), crandallite, goyazite, childrenite, eosphorite, messelite, fairfieldite, collinsite and mitridatite. The substantial number of secondary phosphates at Palermo #2 is a result of alteration of both primary phosphates and associated silicate, carbonate, sulfide, arsenide and oxide minerals locally present in the core margin. Concomitant alteration of these associated minerals contributes the necessary ions to the hydrothermal fluids responsible for the formation of the diverse suite of secondary phosphates. Alteration of the mineral assemblage occurring in a given area creates a set of secondary phosphates characteristic of that specific assemblage, whereas a completely different set of secondary phosphates may appear only a few centimeters away. Thus, each suite of secondary phosphates is the product of its specific microenvironment of alteration.