OXIDIZED AND REDUCED TYPES OF GRANITOIDS IN THE AGADYR ORE DISTRICT, CENTRAL KAZAKHSTAN - COMPARISON OF MINERALOGICAL AND GEOCHEMICAL FEATURES AND INTERACTION WITH THE HOST ROCKS

The Late Hercynian granitoids of the Agadyr' tungsten-molybdenum ore d istrict, Central Kazakhstan, are classified into seven geologic and pe trographic types: #0 - latite dikes, #1 and #2 - monzonite and granodi orite, #3 and #4 - biotite granite, #5 - leucogranite 1, and #6 - leuc ogranite 2. The leucogranite 1 (#5) is the end member of the monzonite -granite-leucogranite differentiation series, a fact inferred from the REE and LILE patterns inherited by the leucogranite, and typical of t he more melanocratic members of the series. The same features of the l eucogranite 2, along with the chemistry of their biotite and the assem blage of their accessory minerals, indicate that the leucogranite 2 (# 6) have no relation to the rock series #0 - #5, but compose a genetica lly independent type of granite. Magmatic-stage metasomatics occur alo ng the contacts of granitoids #1, #2, and #6 with the host rocks. The metasomatics formed due to the infiltration of a magmatic fluid into t he host rocks, as follows from the specific mineralogical and geochemi cal features of the altered near-contact rocks. The calculated T-f(O2) , T-f(HF)/f(H2O) ratios indicate that the #0 - #5 series of granitoids (from mafic to silicic rocks) is a sequence of magma crystallization products formed at oxygen and fluorine fugacities increasing with diff erentiation grade (oxidized type). Conversely, the leucogranite 2 (#6) show features of reduced granitoids (reduced type) with low oxygen an d high fluorine fugacities. The magmatic-stage metasomatic aureoles ne ar the contacts of the oxidized magmas contain the Bt(Mg) + Mag assemb lage, whereas the magmatic-stage metasomatic aureoles near the reduced leucogranite bear the Bt(Fe) + Ilm assemblage. These parageneses char acterize, respectively, the oxidized and the reduced type of the magma tic-stage metasomatic alterations.