Inclusion Characteristics of Yellow-Green Apatite from Mexico

The yellow-green apatite from Mexico is known as "Durango" apatite because of its unique geochemical significance. However, there is less information on its inclusions. Taking the yellow-green apatites from Mexico as the research objects, a comprehensive inclusion study was carried out using the microcamera, Raman spectrometer, and hot and cold table microthermometry, aiming at enriching the inclusions characteristics and origin features of the yellow-green apatites from Mexico. The results show that the yellow-green apatites from Mexico are rich in inclusions, especially fluid inclusions, which can be divided into typeⅠpure liquid inclusions, typeⅡgas-liquid two-phase inclusions (including types Ⅱa and Ⅱb) and type Ⅲ multiphase inclusions with daughter minerals (including types Ⅲa, Ⅲb and Ⅲc) according to phase states. Raman spectrometer detects two daughter mineral components of anhydrite and barite as well as the characteristic 1 285 cm^-1 peak of CO₂. The temperature of ore-forming fluid corresponding to typeⅠand Ⅱ fluid inclusions varies in the range of 106.5-169.6 ℃ and 218.5-546.5 ℃, respectively, and they are low-salinity fluids (0.18-10.73 wt% NaCl eqv). The ore-forming fluid corresponding to type Ⅲ fluid inclusions are with temperatures > 600 ℃ and salinities > 26.30 wt%, indicating that fluid inclusions were trapped in non-uniform state when apatite was formed. The solid inclusions include black pseudohematite, green diopside and transparent feldspar, with pseudohematite appearing most frequently. The metallogenic pressure and depth of apatite from Mexico are estimated to be 39.23-150.70 MPa and 1.31-5.02 km, respectively.