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Published online by Cambridge University Press: 23 December 2005
We present elemental abundance ratios for red giant stars in 9 old halo globular clusters based on the homogeneous data sample and analysis method. Our result suggests that [Si/Ti] ratios in old globular clusters decrease with Galactocentric distances, confirming the previous result by Lee & Carney (2002). We propose that contributions from different masses of the Type II suprenovae progenitors that enriched proto-globular clusters' clouds are responsible for this gradient.