Tonaliteettia

Tonaliteettia is a term used in speculative geology to denote a micrometric silicate phase proposed to occur within tonalite, a felsic plutonic rock. The name combines tonalite with a suffix suggesting a discrete mineralogical entity. In proposed petrogenetic models, tonaliteettia appears as a fine-scale intergrowth that lies between the boundaries of conventional minerals such as feldspar and quartz, contributing a distinctive texture to the rock.

Tonaliteettia is described as an intergrown assemblage dominated by silica- and alumina-rich networks with variable alkali feldspar domains, often showing lamellar or subgrain-scale zoning. Accessory minerals such as zircon, apatite, and fluorite may occur with minor mica. Because it is not yet isolated as a single mineral phase, tonaliteettia is often treated as a microstructural feature rather than a separate chemical end-member.

It is hypothesized to form during late-stage crystallization of tonalite magmas or during metasomatic alteration by silica-rich fluids. Conditions of high fluid activity, temperature gradients, and rapid cooling could promote textural segregation that researchers interpret as tonaliteettia. Geographically, speculative occurrences are described in granitoid terranes where tonalite is common, though no confirmed specimen has been universally recognized.

Detection relies on high-resolution electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction to resolve microtextures and compositional gradients. If validated, tonaliteettia would refine interpretations of magma evolution, chamber crystallization sequences, and crustal fluid-rock interactions in granitoid settings, offering a microtextural proxy for timing and processes in tonalite systems.

At present, tonaliteettia remains a theoretical construct rather than a widely accepted mineral. The term appears in some theoretical discussions and is used to illustrate how microtextures in tonalite could arise. Ongoing petrographic work and advanced analytical techniques are needed to confirm whether tonaliteettia corresponds to a discrete phase or to textural variability within tonalite.