FLUID INCLUSIONS AND VEIN QUARTZ OF NEW CALEDONIAN NICKEL DEPOSITS

The southwest Pacific island of New Caledonia has the third largest lateritic nickel deposit in the world. Fluid inclusions within the quartz veins of the saprolite zone (area of ore concentration) offer an opportunity to identify the fluids responsible for the formation of the deposit. Fluid inclusion data should reveal the source of the fluids involved in the formation of this deposit.

The goal of this research is to determine the nature of the fluids involved in producing the nickel deposits in New Caledonia, in order to determine the source of the ore forming fluids and how deposition occurred. A fluid inclusion study is being performed in order to obtain the pressure, temperature and composition of the ore forming fluid. Understanding the formation of the New Caledonian nickel deposit will lead to a better understanding of other supergene deposits like those in Cuba and the Ural Mountains. It will also increase the understanding of ophiolites, global tectonic and provide new data to aid in mineral exploration.

Samples were collected during the summer of 2010 from river and stream systems. The samples were vuggy, microcrystalline, striated quartz with garnierite filled vugs. The most coarsely crystalline quartz was selected for slide production. Thirteen of the fifteen slides are predominately all quartz with only a few rock fragments, one slide has about 60% garnierite and the one slide is predominately red clays with a little quartz. The majority of the slides have vugs. All of the quartz dominated slides have clear lines of striation indicating that they are vein quartz. The microcrystalline nature of the quartz is evident in the slides with jasperoid quartz.

Analysis of the fifteen fluid inclusion slides has yielded a number of fluid inclusions. Most of the fluid inclusions located are .25 to .75 microns in sizes. The majority of these are within fluid inclusions trails. The inclusions are generally hexagonally shaped some appear to round. Due to the extremely small nature of the fluid inclusions within the trails it has not been possible to identify phases within them. Only one or two fluid inclusions have been found not associated with a fluid inclusion trail. These single inclusions are the larger than the inclusions within the trails. The single occurrence inclusions do appear to be two phase, with a gas bubble within the liquid.