The importance of fractional crystallization and magma mixing in controlling chemical differentiation at Süphan stratovolcano, eastern Anatolia, Turkey

There are well established differences in the chemical and isotopic characteristics of the calc-alkaline basalt—andesite-dacite-rhyolite association of the northern (n.v.z.), central (c.v.z.) and southern volcanic zones (s.v.z.) of the South American Andes. Volcanic rocks of the alkaline basalt-trachyte association occur within and to the east of these active volcanic zones. The chemical and isotopic characteristics of the n.v.z. basaltic andesites and andesites and the s.v.z. basalts, basaltic andesites and andesites are consistent with derivation by fractional crystallization of basaltic parent magmas formed by partial melting of the asthenospheric mantle wedge containing components from subducted oceanic lithosphere. Conversely, the alkaline lavas are derived from basaltic parent magmas formed from mantle of ‘within-plate’ character. Recent basaltic andesites from the Cerro Galan volcanic centre to the SE of the c.v.z. are derived from mantle containing both subduction zone and within-plate components, and have experienced assimilation and fractional crystallization (a.f.c.) during uprise through the continental crust. The c.v.z. basaltic andesites are derived from mantle containing subduction-zone components, probably accompanied by a.f.c. within the continental crust. Some c.v.z. lavas and pyroclastic rocks show petrological and geochemical evidence for magma mixing. The petrogenesis of the c.v.z. lavas is therefore a complex process in which magmas derived from heterogeneous mantle experience assimilation, fractional crystallization, and magma mixing during uprise through the continental crust.

Download Full-text

Magma mixing, fractional crystallization and volatile degassing during the 1883 eruption of Krakatau volcano, Indonesia

Journal of Volcanology and Geothermal Research ◽

10.1016/s0377-0273(96)00060-1 ◽

1996 ◽

Vol 74 (3-4) ◽

pp. 243-274 ◽

Cited By ~ 78

Author(s):

Charles W. Mandeville ◽

Steven Carey ◽

Haraldur Sigurdsson

Keyword(s):

Fractional Crystallization ◽

Magma Mixing ◽

Krakatau Volcano

Download Full-text

Field, geochemical, and isotopic evidence for magma mixing and assimilation and fractional crystallization processes in the Quottoon Igneous Complex, northwestern British Columbia and southeastern Alaska

Canadian Journal of Earth Sciences ◽

10.1139/e99-001 ◽

1999 ◽

Vol 36 (5) ◽

pp. 819-831 ◽

Cited By ~ 14

Author(s):

J B Thomas ◽

A K Sinha

Keyword(s):

British Columbia ◽

Fractional Crystallization ◽

Magma Mixing ◽

Parental Magma ◽

Geochemical Data ◽

Igneous Complex ◽

Source Regions ◽

Magmatic Body ◽

Color Indices ◽

Lower Crustal

The quartz dioritic Quottoon Igneous Complex (QIC) is a major Paleogene (65-56 Ma) magmatic body in northwestern British Columbia and southeastern Alaska that was emplaced along the Coast shear zone. The QIC contains two different igneous suites that provide information about source regions and magmatic processes. Heterogeneous suite I rocks (e.g., along Steamer Passage) have a pervasive solid-state fabric, abundant mafic enclaves and late-stage dikes, metasedimentary screens, and variable color indices (25-50). The homogeneous suite II rocks (e.g., along Quottoon Inlet) have a weak fabric developed in the magmatic state (aligned feldspars, melt-filled shears) and more uniform color indices (24-34) than in suite I. Suite I rocks have Sr concentrations <750 ppm, average LaN/YbN = 10.4, and initial 87Sr/86Sr ratios that range from 0.70513 to 0.70717. The suite II rocks have Sr concentrations >750 ppm, average LaN/YbN = 23, and initial 87Sr/86Sr ratios that range from 0.70617 to 0.70686. This study suggests that the parental QIC magma (initial 87Sr/86Sr approximately 0.706) can be derived by partial melting of an amphibolitic source reservoir at lower crustal conditions. Geochemical data (Rb, Sr, Ba, and LaN/YbN) and initial 87Sr/86Sr ratios preclude linkages between the two suites by fractional crystallization or assimilation and fractional crystallization processes. The suite I rocks are interpreted to be the result of magma mixing between the QIC parental magma and a mantle-derived magma. The suite II rocks are a result of assimilation and fractional crystallization processes.

Download Full-text

The Loch Scridain Xenolithic Sill Complex, Isle of Mull, Scotland: Fractional Crystallization, Assimilation, Magma-Mixing and Crustal Anatexis in Subvolcanic Conduits

Journal of Petrology ◽

10.1093/petroj/39.3.519 ◽

1998 ◽

Vol 39 (3) ◽

pp. 519-550 ◽

Cited By ~ 18

Author(s):

R. J. Preston ◽

B. R. Bell ◽

G. Rogers

Keyword(s):

Fractional Crystallization ◽

Magma Mixing ◽

Crustal Anatexis

Download Full-text

Volcanological and magmatological evolution of Stromboli volcano (Aeolian Islands): The roles of fractional crystallization, magma mixing, crustal contamination and source heterogeneity

Bulletin of Volcanology ◽

10.1007/bf01056897 ◽

1989 ◽

Vol 51 (5) ◽

pp. 355-378 ◽

Cited By ~ 100

Author(s):

Lorella Francalanci ◽

Piero Manetti ◽

Angelo Peccerillo

Keyword(s):

Fractional Crystallization ◽

Magma Mixing ◽

Crustal Contamination ◽

Stromboli Volcano ◽

Aeolian Islands ◽

Source Heterogeneity

Download Full-text

Cryptic variation in the Rhum layered intrusion

Mineralogical Magazine ◽

10.1180/minmag.1978.042.323.04 ◽

1978 ◽

Vol 42 (323) ◽

pp. 347-356 ◽

Cited By ~ 49

Author(s):

A. C. Dunham ◽

W. J. Wadsworth

Keyword(s):

Magma Chamber ◽

Fractional Crystallization ◽

Electron Microprobe ◽

Magma Mixing ◽

Layered Intrusion ◽

The Other ◽

Layered Series ◽

Cryptic Variation ◽

High Calcium

SummaryElectron-microprobe analyses of cumulus olivine, chromite, pyroxene, and plagioclase from layered peridotites and allivalites of the Eastern and Western Layered Series of Rhum demonstrate the presence of cryptic variation. Olivine varies from Fo88-78 within individual units, and there are corresponding changes in the Mg/(Mg+Fe2+) ratios in the pyroxenes and chromites. Plagioclase changes are not so dramatic, but the An-content broadly follows the Mg/(Mg+Fe2+) ratio in the other minerals. The most Fe-(and Na-) rich phases do not occur at the top of lithological units, but some way below. The composition trend above them is reversed. The data are interpreted as the result of periodic infilling of a magma chamber, the new magma mixing with the remains of the previous pulse. Each pulse was followed by a period when fractional crystallization produced the layered rocks. New data on Ni in the olivines suggests that the ratio of the volume of initial magma to volume of layered rocks was about four to one, the initial magma being allied to the high-calcium low-alkali tholeiitic basalts of Skye.

Download Full-text