ions ▁are ▁w ides p read ▁in ▁an orth oc l ase ▁and ▁h eden berg ite ▁phen oc ry st s , ▁as ▁well ▁as ▁in ▁r ar er ▁quart z ▁and ▁f ay al ite ▁phen oc ry st s . ▁Compar ing ▁the ▁relative ▁en rich ments ▁of ▁in compatible ▁vol atile ▁and ▁non vol atile ▁elements ▁in ▁m elt ▁inclus ions ▁along ▁a ▁liquid ▁line ▁of ▁descent ▁shows ▁decre asing ▁vol atile / Z r ▁r ati os ▁suggesting ▁the ▁partition ing ▁of ▁vol at iles ▁into ▁a ▁fluid ▁phase . ▁This ▁suggests ▁that ▁current ▁gas - y ield ▁estimates ▁( H orn ▁& ▁Sch min ke , ▁ 2 0 0 0 ) ▁for ▁the ▁Mill en ni um ▁er u ption , ▁based ▁on ▁the ▁pet ro logic ▁method ▁( d ifference ▁in ▁vol at iles ▁between ▁m elt ▁inclus ions ▁and ▁matrix ▁glass ), ▁could ▁be ▁severe ▁under est im ates . ▁ ▁Cl imate ▁effects ▁ ▁The ▁Mill en ni um ▁er u ption ▁is ▁thought ▁to ▁have ▁em itted ▁an ▁enorm ous ▁mass ▁of ▁vol at iles ▁into ▁the ▁str atos phere , ▁likely ▁resulting ▁in ▁a ▁major ▁world wide ▁clim atic ▁impact , ▁though ▁more ▁recent ▁studies ▁indicate ▁that ▁the ▁Mill en ni um ▁er u ption ▁of ▁Ch ang ba ish an ▁vol cano ▁may ▁have ▁been ▁limited ▁to ▁regional ▁clim atic ▁effects . ▁However , ▁there ▁are ▁some ▁meteor ological ▁anom al ies ▁in ▁A . D . ▁ 9 4