FLUID INCLUSION STUDY OF THE NEOPROTEROZOIC NAGTHAT SILICICLASTIC SEDIMENTS, NW KUMAUN LESSER HIMALAYA - IMPLICATIONS TO QUARTZ CEMENTATIONHISTORY

The fluid inclusion study in quartz overgrowth in the siliciclastics o f Neoproterozoic Nagthat Formation reveals that the quartz cementation took place in the range of 80 degrees C to 130 degrees C with a salin ity range of 0.82 to 9.18 wt.% NaCl. The microthermometric data, combi ned with petrographic and geologic evidences permitted to constrain th e nature bf cementing fluids and source of cement. The silica for quar tz cementation was derived partly from both the internal source (quart z and feldspar dissolution) and external source (pore fluids). It can be further suggested that the qyuartz cementation in the lower stratig raphic level (near the Chandpur Formation) is mainly by marine water w hile in the upper stratigraphic level (near the Blaini Formation), met eoric water has played an important role for the same.