1 ESTIMATING CONDITIONS OF BASALT MAGMA FORMATION BY CLINOPYROXENE COMPOSITIONS

• Main Authors: Migdisova N. A, Sushchevskaya N. M, Arto V. Luttinen, Mikhalsky E. V
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Bouvet; Dronning Maud Land; Hobbs; Hobbs Coast; Indian; Antarc*; Antarctica; Hobbs coast
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.563.2954; http://geo.web.ru/conf/khitariada/1-2003/informbul-1_2003/magm-6e.pdf

We have compared a lot of compositions of clinopyroxene from different types of basaltic lavas. We have studied tholeiites, traps and alkaline magmas that are common in Antarctica and nearby region of Southern Atlantic. Grains of clinopyroxene were picked from basaltic magmas of different ages: from tholeiites formed in the region of Western End of South-West Indian Ridge (SWIR) [1] to Cenozoic alkaline lavas erupted in the segment of Hobbs Coast (Western Antarctic) [2] and Mesozoic basaltic flows related with traps in the region of Dronning Maud Land Province (DMLP) [3]. All magmas are of olivine-bearing type. The petrogenetic compare of clinopyroxene from basalts from the Spiess Ridge and from the segment of Southwest Indian Ridge in the Bouvet region showed that paragenesis of minerals is similar and consists of olivine, plagioclase and clinopyroxene. Composition of clinopyroxenes from the Hobbs Coast and DMLP are similar by Mg # ( interval– 50-85). Clinopyroxenes of SWIR different by more Mg # up to 76-90. Clinopyroxenes from alkaline Hobbs Coast province enriched by Al2O3, Na and depleted by Cr. Variations of Cr2O3 / Al2O3 for the analyzed clinopyroxenes are shown in fig.1. The DMLP clinopyroxenes distinguish by more high level of Cr2O3 / Al2O3 for clinopyroxenes with Mg # = 80-85. Using method for determent the pressures of fractionation of melts by Nimis [4], which are based