New (U-Th)/He age constraints on the emplacement of kimberlite pipes in north-eastern Kansas Blackburn, T. ; Stockli, D. ; Carlson, R. W. ; Berendson, P. ; Walker, J. D. ; Winters, N. D. Abstract Publication: Geochimica et Cosmochimica Acta Supplement Pub Date: May 2005 Bibcode: 2005GeCAS..69..859B