1. Melting in the Crust: Granitoids Yosemite National Park

2. Granitoid Intrusions Several 10,000 cubic km 3

3. Classification of Granitic Rocks ~80% are monzogranites Biotite, hornblende and px are common accessories.

4. Classification: Porphyrys Common in shallow intrusions Associated with Mo and Cu mineralisation

5. Aplites Aplite - “unspectacular”

6. Pegmatites

8. Granophyres Graphic texture

9. Classification: Depth of Emplacement

10. Classification: Hypersolvus Granite Orthoclase with perthite (albite lamellae). One feldspar

11. Subsolvus Granite Orthoclase with perthite (albite lamellae). Two feldspars Albite with orthoclase But: Only in Alkali Granites – plagioclase causes problems!

12. Classification: Timing of Emplacement Post tectonic - after deformation Syntectonic - during deformation (mesozone, catazone) Pretectonic - before deformation (catazone)

13. Nature of Granitic Intrusions Epizone - also plugs, dykes, sills and laccoliths. Mesozone - batholiths, stocks

14. Emplacement - The Space Problem

15. External Contacts

16. migmatite

17. Melting in the Crust Small degrees of partial melting of andesitic crust will lead to monzogranite

18. Melting in the Crust Melting related to the dehydration of biotite and muscovite

19. Chemical (Tectonic) Types of Granite S-type Granites high 87 Sr/ 86 Sr I-type Granites low 87 Sr/ 86 Sr A-type Granites low 87 Sr/ 86 Sr

20. Chemical (Tectonic) Types of Granite I-type Granites S-type Granites M-type Granites A-type Granites M-type Granites

21. Continental Arc Granitoids S-type granites further from subduction zone. 87 Sr/ 86 Sr decreases towards subduction zone Silica content decreases towards subduction zone (I.e. granites to qtz diorites). More assimilation of crust/less magmatic rock away from subduction zone.

22. Heat Sources

25. Related Rocks: Lamprophyres Igneous rocks dominated by phenocrysts of hydrous minerals (biotite/phlogopite/hornblende. Often contain feldspathoids in groundmass Found as plugs and dykes associated with granitoid rocks. High Nb/Ti (metasomatised mantle) Enriched in incompatibles (low degrees of partial melting)

26. Lamprophyre Mantle Melts Lamprophyres late-stage mantle melts?