Lithium in amphiboles; detection, quantification, and incorporation mechanisms in the compositional space bridging sodic and (super B) Li-amphiboles

Systematic analysis of the available chemical and structural data constrains Li in amphiboles to the following compositions and exchange vectors: 1) (super B) Li is incorporated according to (super M4') Li (super M4) Li (sub -1) , and no apparent miscibility gap, 2) (super C) Li is incorporated according to (super M3) Li (super M3) Fe (super 3+M3) Fe (super 2+) (sub -1) (super M2) Fe (super 2+) (sub -1) ; however, a partial bond-strength contribution is provided by the Si at the T1 site and by Na or K at the Am site. Amphiboles with (super C) Li > 0.5 pfu (root names leakeite, kornite, whittakerite and pedrizite) have more than half-occupied A-group sites. Seven new amphibole end-members containing Li have been discovered in 'episienites' (dequartzified and albitized granites) from the Predriza massif, central Spain, where Li incorporation and partitioning is controlled both by the composition of the fluid and T of crystallization. This occurrence provides a unique opportunity to characterize the (super M4) Li [] (super M4) Na and (super M3) Li [] (super M3) Fe (super 2+) solid solutions. Analysis of available data provides criteria for calculating reliable H (sub 2) O and Li (sub 2) O values as well as for obtaining reliable unit formulae from routine EPMA results.