Geochemistry of Guli dunites.

Kogarko L.N., Kuzmin D.

GEOKHI RAS

GMI SO RAS

 

Guli massif is a complex multiphase intrusion. Dunite represents about 60% of Guli territory  however the main part of dunite is covered by sedimentary rocks.About 60% of massif territory

Dunites consists of 80-90% of olivine and characterized by cumulative texture.Pyroxenes and  spinel  occur in interstitial  space. In dunites we  also found apatite , perovskite ,carbonates, native gold and silver .

Dunites are strongly serpentinised . We investigated the  dunite composition from different part of Guli massif. The range of chemical composition of dunite from different part  is not very large.Concentrations of Calsium and Cromium are  mostly variable.We believe that this variation s are result from different parts of hosted interstitial material. Quantity of interstitial material in dunite falls in the range 15-1% Averarge composition of dunite is represented in tabl 1.

 

	SiO2	TiO2	Al2O3	Fe2O3	FeO	MnO	MgO	CaO	Na2O	K2O	P2O5	Cr2O3	Сумма
Дуниты (среднее)	36,95	0,45	0,39	4,65	8,36	0,19	42,52	1,35	0,06	0,01	0,06	0,960	95,95
Косьвиты (среднее)	38,23	5,34	2,45	7,89	11,94	0,25	17,40	15,41	0,38	0,12	0,79	0,17	100,37

 

Rare elements were analysed by ICPMS and laser ablation.Rear Eart distribution in ofiolitic dunites  is very flat but in Guli dunites all REE spectra show light REE enrichment  that  is typical for ultramafic alkaline complexes.We suggest that kosvites were formed as result of separation of interstitial material from Guli dunites.This is the reason that kosvites contain higher concentration such elements as Ca, Zr, REE,Sr etc. as compare as dunite.

 

REE in dunites

 

REE in kosvites