I am wondering about the oxides mineralogy and chemistry. Does anyone knows the details of ilmenite-rutile occurrences, mineralogy, mineral chemistry and zone of concentration of these minerals in Chilas complex?
Literature, reports, Pictures?
Dear Mr. Ali Mahar,
I am not familiar with the regional geology of the area you are going to refer to but I am dealing with rutile-ilmenite intergrowth textures also named "nigrine". Can you give some more details as to the microscopic texture of these Ti mineral associations.
Sorry for not providing you with an answer pertinent to your question.
H.G.Dill
Dear Munazzam: The Chilas Zoned Complex is considered as the root of the famous Kohistan Arc, in the Karakorum Range. It is a very large and complex intrusion, actually at least made of two main intrusions, encompassing ultramafic to intermediate plutonic rocks. This article explains the petrology and mineral chemistry of the whole Complex, however there's no mention of rutile-ilmenite seggregations in the anorthosites, only of Cr-spinel and chromite seams in the ultramafics:
Oliver Jagoutz1,2,*, Othmar Müntener2,†, Peter Ulmer1, Thomas Pettke2, Jean-Pierre Burg1, Hamid Dawood3 and Shahid Hussain3Petrology and Mineral Chemistry of Lower Crustal Intrusions: the Chilas Complex, Kohistan (NW Pakistan), Journal of Petrology, Volume 48, Issue 10: 1895-195.
You can download it for free at the following link:
http://petrology.oxfordjournals.org/content/48/10/1895.full
P.D.: one of my life's dreams is be to able someday to travel the Karakorum Highway and enjoy all the fabulous rock section which outcrops along it, which cut the complete Kohistan Arc and part of the Himalayan Suture. At same point there are gigantic hornblende crystals 30 m long and 5 m wide: a real sight!
Dear Munazzam,
I can say with a fair degree of confidence that I have seen more parts of the Chilas complex and studied more thin sections than anyone else. My studies have covered exposures of the complex in Swat (extensively), Dir, Indus valley and Thak-Buto Gah sections south of Chilas. Dr Asif Khan worked extensively on the complex, mostly in the Indus-Thak region. Between me and Asif, we have thousands of microprobe analyses.I do not remember to have identified rutile in the Chilas, possibly barring the amphibolitized parts. I, M Asif Khan and Brian F Windly published a paper on magnetite-ilmenite phases of the Chilas in the Peshawar journal in 1989, and on Cr-spinels in 1992 in American Mineralogis 77, 1074-79.
I got lost in too many things and did nor respond to your questions on Besham area and Khewara trap. Will get back to you soon on this. my apologies.
Best, Qasim
Dear Qasim Jan,
Not even as an altered product of ilmenite? Currently, I am examining some ilmenite-rutile thin sections of anorthosite complex in Mexico. I believe that the rutile in anorthosites is basically an altered product of ilmenite instead being magmatic particularly, if the anorthosite has spatially related metamorphic belt. What you think?
Dear Munazzam,
Pl give me three weeks to recheck. All my geology facilities and collections are in Geology Centre in Peshawar, where I am Prof Emeritus. However, I am spending more time in Islamabad because of full-time job. I shall be abroad in early December, but hope to be in Peshawar in mid December. That will be the time I can check my thin sections again. I would look into gabbronorites (most of which are plagioclase-rich, with
Dear Sebastián Grande,
Yes, I saw that paper,
And certainly, this is a wonderful place for a geologist
Dear Harald G. Dill,
Well, for Chilas, I do not know much, but, I saw ilmenite-rutile, in anorthosites from Mexico, if by intergrowth you mean that both grew as magmatic minerals? I am not sure, but in the BSE images (in some of your papers) rutile seems to be an alteration product of ilmenite? The rutile of Mexico had 12000ppm Nb, Did you encounter this much higher Nb content in rutile?