APATITE OF THE DUFEK INTRUSION: DISTRIBUTION, PARAGENESIS, AND CHEMISTRY

• Main Author: James L. Drinkwater
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: apatite; Dufek intrusion; phosphoruSl ror€-anfth elements; Antarctica; Forrestal Range; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.612.6945; http://rruff.info/doclib/cm/vol28/CM28_835.pdf

Apatite in the Dufek intrusion of Antarctica is F-rich and exhibits systematic variations in contents of Cl, F, Fe, Sr, and rare-earth elements (R.E'Es). Four types of apatite are distinguished on the basis of morphology, grain size, and textural relations: l) cumulus, 2) arly postcumulus (euhedral forms), 3) late postcumulus (anhedral forms), and 4) noncumulus primocryst. Cumulus apatite is relatively rich in F, Fe, and Sr, and poor in Cl and ZREEs, whereas postcumulus apatite commonly contains more Cl and LREE*, and less F than cumulus apatite. Apatite primocrysts of the capping granophyre are depleted in Cl and enriched in REEs. Cl, F, Fe, and R.EEs are partitioned between the two types of postcumulus apatite, with euhedral, early-postcumulus grains typically containing less F, more Cl and Fe, and having higher Ce,/Y ratios than anhedral, late-postcumulus grains. Large subhedral apa-tite sporadically occurs in anorthosite and leucogabbro below the main cumulus-apatite horizon, and shows tex-tural and chemical evidence ofbeing recycled cumulus apa-tite, deposited by current activity. Whole-rock P contents follow patterns generally comparable to those described for other layered mafic intrusions, but are unusually high in cumulates of the Forrestal Range section. Iron-rich biotite occurs in thin (5-15 pm) infilled cavities parallel to the c axes of some well-formed cumulus and early-postcumulus apatite crystals.