International Geologiical Congress - Oslo 2008

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MPM-01 General contributions to mineralogy

 

Occurence and mineralogy of serpentine minerals in the calc-silicate rock sheets from bonghwa, South Korea

 

Sungwo Bae, Pusan National University (Republic of Korea)
Jinyeon Hwang, Pusan National University (Republic of Korea)
Kyuwon Kwack, Pusan National University (Republic of Korea)
Jiho Oh, Pusan National University (Republic of Korea)
Hyomin Lee, Pusan National University (Republic of Korea)
 

 

Calc-silicate rock sheet occurs within the Precambrian metasedimentary rocks consisting of chlorite schist, biotite-sillimanite schist, quartz-biotie schist, mica-chlorite schist and well-crystallized limestone. Calc-silicate rock runs parallel to bedding plane with 16-20 meters in width. Calcite, dolomite, serpentine and tremolite are occurred as major minerals and talc is occurred as a miner mineral. Serpentine mainly occurs in the upper part and tremolite occurs in lower part of calc-silicate rock sheet. Colors of calc-silicate rock change to deeper green with increasing amounts of serpentine mineral. XRD, FT-IR analyses indicates that serpentine mineral is antigorite. Platy structure of antigorite is well observed by SEM analysis. EPMA data indicates that chemical composition of antigorite is very close to ideal (SiO2: 44.3 wt.% and MgO: 40.8 wt.%). The chemical formula of antigorite is calculated as Mg2.82Al0.04Fe3+0.04Si2.05O5(OH)4. Cations in octahedral site are analyzed as lesser (2.90) than ideal (3.00), and this is due to modulated structure of antigorite. From careful study by comparing mineralogical analysis data and occurrence, calc-silicate rock sheet was formed by metamorphism of calcareous sedimentary rocks having different mineralogical and chemical compositions. It is considered that the host rock of serpentine enriched upper part was more Mg-rich rocks than the host rocks of tremolite enriched lower part. Serpentine and tremolite formed by syngenetic process.

 

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