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WelsforLeabharlann Baidu complex 5 samples
Evisa Complex of Corsica 15 samples
Shira complex 11 samples
Lachlan Fold Belt 25 samples
published analyses 17 samples
I- and S-type granites 1569 samples Lachlan Fold Belt of Austrlia
➢ Other processes, such as different degrees of partial melting or removal of successive batches of magma from a suitable source, might also produce ranges of subalkaline to peralkaline magmas.
M-type granites 17 samples New Britain
Geochemistry
Table1. Average compositions of various granites types
SiO2
Chemical discrimination
Fig 1. Ga/Al versus certain major elements
Petrogenesis
3.Partial melting model
➢ A-type granites partial melting at elevated temperatures of an essentially anhydrous source which has been depleted in water by extraction of a minimum-melt I-type magma.
Differentiation has produced minor volumes of granite with a partial A-type signature. Even in these cases, Atype granites can be distinguished from non-A-type magmas. , we are aware of no evidence that differentiation alone could produce the distinctive chemistry of granites.
Petrogenesis
1.Metasomatic model
Metasomatism
The peralkaline character of anorogenic granites results from metasomatism by CO2 and halogen-rich volatile phase during and after emplacement
Granite classification
Granitoid rocks
Orogenic granites
(造山带花岗岩)
Anorogenic granites
(非造山带花岗岩)
economic potential and tectonic significance
A-type granites Alkaline
➢ However, individual A-type granite suites exhibit considerable variation in chemical composition, and grade towards I- and S-type granite compositions.
S
A
I S
IS M
A IS
I M
A
S I
S I M
A
IS
M IS
Chemical discrimination
Fig 2. Ga/Al versus certain trace elements
A
A
A
A A AA
Chemical discrimination
Fig 3. Zr+Nb+Ce+Y versus major elements ratios
explain either the chemical differences between the two
types or the homogeneous character of many subalkaline A-type
plutons.
Petrogenesis
2.Differentiation model
explain both the gardation from strongly alkaline
compositions to more normal granite compositions, and the
restriction of Sn-W-Mo mineralization to subalkaline phases.
A-type granites: geochemical characteristics, discrimination and petrogenesis
Fei Hong
Department of Earth Science
Content
➢ Granite classifications ➢ Geochemistry ➢ Chemical discrimination ➢ Petrogenesis ➢ Tectonic implications
Anhydrous Anorogenic Aluminous Ambiguous
Samples
A-type granites 148 samples
Topsails igneous terrane 72 samples
Seal Island Bight complex 2 samples
Saint Lawrence granite 1 samples
A
A
3
Chemical discrimination
Fig 4. Zr+Ce+Y versus Rb/Ba
44
Chemical discrimination
COLG, VAG, WPG and ORG granites
5
Petrogenesis
➢ Metasomatic model ➢ Differentiation model ➢ Partial melting model
Evisa Complex of Corsica 15 samples
Shira complex 11 samples
Lachlan Fold Belt 25 samples
published analyses 17 samples
I- and S-type granites 1569 samples Lachlan Fold Belt of Austrlia
➢ Other processes, such as different degrees of partial melting or removal of successive batches of magma from a suitable source, might also produce ranges of subalkaline to peralkaline magmas.
M-type granites 17 samples New Britain
Geochemistry
Table1. Average compositions of various granites types
SiO2
Chemical discrimination
Fig 1. Ga/Al versus certain major elements
Petrogenesis
3.Partial melting model
➢ A-type granites partial melting at elevated temperatures of an essentially anhydrous source which has been depleted in water by extraction of a minimum-melt I-type magma.
Differentiation has produced minor volumes of granite with a partial A-type signature. Even in these cases, Atype granites can be distinguished from non-A-type magmas. , we are aware of no evidence that differentiation alone could produce the distinctive chemistry of granites.
Petrogenesis
1.Metasomatic model
Metasomatism
The peralkaline character of anorogenic granites results from metasomatism by CO2 and halogen-rich volatile phase during and after emplacement
Granite classification
Granitoid rocks
Orogenic granites
(造山带花岗岩)
Anorogenic granites
(非造山带花岗岩)
economic potential and tectonic significance
A-type granites Alkaline
➢ However, individual A-type granite suites exhibit considerable variation in chemical composition, and grade towards I- and S-type granite compositions.
S
A
I S
IS M
A IS
I M
A
S I
S I M
A
IS
M IS
Chemical discrimination
Fig 2. Ga/Al versus certain trace elements
A
A
A
A A AA
Chemical discrimination
Fig 3. Zr+Nb+Ce+Y versus major elements ratios
explain either the chemical differences between the two
types or the homogeneous character of many subalkaline A-type
plutons.
Petrogenesis
2.Differentiation model
explain both the gardation from strongly alkaline
compositions to more normal granite compositions, and the
restriction of Sn-W-Mo mineralization to subalkaline phases.
A-type granites: geochemical characteristics, discrimination and petrogenesis
Fei Hong
Department of Earth Science
Content
➢ Granite classifications ➢ Geochemistry ➢ Chemical discrimination ➢ Petrogenesis ➢ Tectonic implications
Anhydrous Anorogenic Aluminous Ambiguous
Samples
A-type granites 148 samples
Topsails igneous terrane 72 samples
Seal Island Bight complex 2 samples
Saint Lawrence granite 1 samples
A
A
3
Chemical discrimination
Fig 4. Zr+Ce+Y versus Rb/Ba
44
Chemical discrimination
COLG, VAG, WPG and ORG granites
5
Petrogenesis
➢ Metasomatic model ➢ Differentiation model ➢ Partial melting model