Trondhjemite

The name and its history

Victor M. Goldschmidt (1916), reported; primary publication not yet page-checked · 1916 (secondary attestation)

What does the word literally mean?

Literal naming sense: rock of Trondheim. Immediate language/formation: Norwegian city-name, older spelling Trondhjem. Spelling of the name records an older city name rather than an ancient Greek compound.

What did the original author mean?

Goldschmidt used the old spelling of Trondheim for a distinctive pale, plagioclase-rich Norwegian intrusive rock.

Why was the name needed?

An ordinary tonalite or granite label did not convey the conspicuous sodic, leucocratic assemblage.

What evidence supported the original concept?

Norwegian intrusive-rock descriptions and their mineralogical composition.

How has geology changed the concept?

Now used as a special tonalite variant and in the TTG (tonalite–trondhjemite–granodiorite) association of ancient crust; it has no separate QAP field.

Further historical context

Goldschmidt used the old spelling of Trondheim for a distinctive pale, plagioclase-rich Norwegian intrusive rock.

An ordinary tonalite or granite label did not convey the conspicuous sodic, leucocratic assemblage.

Norwegian intrusive-rock descriptions and their mineralogical composition.

Now used as a special tonalite variant and in the TTG (tonalite–trondhjemite–granodiorite) association of ancient crust; it has no separate QAP field.

Related names

Tonalite · Granodiorite · Leucocratic · Plagioclase · Archean

Sources

1. Trondhjemite, rock history and classification — Victor Goldschmidt 1916 attribution and current leucotonalite meaning
2. BGS, Rock Classification Scheme — Modern descriptive rock-naming principles and definitions
3. USGS, Lithologic classification of geologic map units — Modal definitions and named plutonic-rock categories
4. IUGS / Le Maitre et al. (2002), Igneous Rocks: A Classification and Glossary of Terms, ch. 3 — Authoritative IUGS rock-name history and bibliographic attributions