Magma mixing/mingling in the Eocene Horoz (Nigde) granitoids, Central southern Turkey: evidence from mafic microgranular enclaves

作者：Kocak Kerim^*; Zedef Veysel; Kansun Gursel

来源：Mineralogy and Petrology, 2011, 103(1-4): 149-167.

DOI：10.1007/s00710-011-0165-7

Mafic microgranular enclaves (MMEs) are widespread in the Horoz pluton with granodiorite and granite units. Rounded to elliptical MMEs have variable size (from a few centimetres up to metres) and are generally fine-grained with typical magmatic textures. The plagioclase compositions of the MMEs range from An(18)-An(64) in the cores to An(17)-An(29) in the rims, while that of the host rocks varies from An(17) to An(55) in the cores to An(07) to An(33) in the rims. The biotite is mostly eastonitic, and the calcic-amphibole is magnesio-hornblende and edenite. Oxygen fugacity estimates from both groups' biotites suggest that the Horoz magma possibly crystallised at fO(2) conditions above the nickel-nickel oxide (NNO) buffer. The significance of magma mixing in their genesis is highlighted by various petrographic and mineralogical characteristics such as resorption surfaces in plagioclases and amphibole; quartz ocelli rimmed by biotite and amphibole; sieve and boxy cellular textures, and sharp zoning discontinuities in plagioclase. The importance of magma mixing is also evident in the amphiboles of the host rocks, which are slightly richer in Si, Fe3+ and Mg in comparison with the amphiboles of MMEs. However, the compositional similarity of the plagioclase and biotite phenocrysts from MMEs and their host rocks suggests that the MMEs were predominantly equilibrated with their hosts. Evidence from petrography and mineral chemistry suggests that the adakitic Horoz MMEs could be developed from a mantle-derived, water-rich magma (> 3 mass%) affected by a mixing of felsic melt at P > 2.3 kbar, T > 730A degrees C.

• 出版日期2011-11