Jun, 2017
The occurrence of fluor-wagnerite in UHT granulites and its implications towards understanding fluid regimes in the evolution of deep crust: a case study from the Eastern Ghats Belt, India
MINERALOGY AND PETROLOGY
- ,
- ,
- ,
- ,
- Volume
- 111
- Number
- 3
- First page
- 417
- Last page
- 429
- Language
- English
- Publishing type
- Research paper (scientific journal)
- DOI
- 10.1007/s00710-016-0474-y
- Publisher
- SPRINGER WIEN
We report the occurrence of a rare phosphate mineral, fluor-wagnerite (Mg1.91-1.94Fe0.06-0.07Ca < 0.01) (P0.99-1.00O4)(OH0.02-0.17F0.98-0.83) from the Eastern Ghats Belt of India, an orogenic belt evolved during Meso- to Neoproterozoic time. The host rock, i.e. high- to ultrahigh temperature (UHT) granulites (similar to 1000 degrees C, 8-9 kbar) of the studied area was retrogressed after emplacement to mid-crustal level (800-850 degrees C, 6-6.5 kbar) as deduced from their pressure-temperature histories. Based on mineral chemical data and micro-Raman analyses, we document an unusual high Mg-F-rich chemistry of the F-wagnerite, which occur both in peak metamorphic porphyroblastic assemblages as well as in the retrograde matrix assemblage. Therefore, in absence of other common phosphates like apatite, fluor-wagnerite can act as an indicator for the presence of F-bearing fluids for rocks with high X (Mg) and/or fO(2). The occurrence of F-rich minerals as monitors for fluid compositions has important implications for the onset of biotite dehydration melting and hence melt production in the deep crust. We propose that fluor-wagnerite can occur as an accessory mineral associated with F-rich fluids in lower-mid crustal rocks, and F in coexisting minerals should be taken into consideration when reconciling the petrogenetic grid of biotite-dehydration melting.
- Link information
- ID information
-
- DOI : 10.1007/s00710-016-0474-y
- ISSN : 0930-0708
- eISSN : 1438-1168
- Web of Science ID : WOS:000401789200009