Settling　particles　were　sampled　monthly　for　1　year　using　an　automated　time-series　sediment　trap　positioned　at　similar　depths　at　two　sites　of　high　diatomaceous　productivity　in　the　North　Pacific　Ocean　and　Bering　Sea.　The　particles　were　analyzed　for　rare　earth　elements　(REEs)　by　inductively　coupled　plasma　mass　spectrometry　(ICP-MS)　with　and　without　chemical　treatment　of　the　bulk　samples　to　isolate　siliceous　fractions.　The　REE　composition　of　the　bulk　samples　is　explained　largely　by　the　contribution　of　two　distinct　components:　(i)　carbonate　with　a　higher　REE　concentration,　a　negative　Ce　anomaly　and　lighter　REE　(LREE)　enrichment;　(ii)　opal　with　a　lower　REE　concentration,　a　weaker　negative　Ce　anomaly　and　heavier　REE　(HREE)　enrichment.　The　siliceous　fractions　of　settling　particles　are　characterized　by　high　Si/Al　ratios　(30-190),　reflecting　high　diatom　productivity　at　the　studied　sites.　The　La/Al　ratio　of　the　siliceous　fraction　is　close　to　that　of　the　upper　crust,　but　the　Lu/Al　and　Lu/La　ratios　are　significantly　higher　than　those　of　the　upper　crust　or　airborne　particles,　indicating　the　presence　of　excess　HREEs　in　the　siliceous　fraction.　Diatoms　are　believed　to　be　important　carriers　of　HREEs.　The　Ce　anomaly,　Eu　anomaly,　slope　of　the　REE　pattern,　and　Sigma　REE　of　the　siliceous　fraction　vary　exponentially　with　decreasing　total　mass　flux.　They　can　be　well-reproduced　according　to　the　differential　dissolution　kinetics　of　elements　in　the　order　of　Ce　＜　lighter　REEs　(LREEs)　＜　Eu　=　heavier　REEs　(HREEs)　＜　Si　from　settling　particles,　where　the　dissolution　rate　is　critically　reduced　through　particle　aggregation.　This　order　is　consistent　with　the　vertical　distribution　of　dissolved　REEs　and　Si　in　oceans.　The　differential　dissolution　kinetics　leads　to　HREE　enrichment　of　the　original　diatoms　and　REE　enrichment　of　dissolved　diatoms.　The　Lu/Si　ratio　of　the　siliceous　fraction　of　settling　particles　recovered　from　some　of　the　highest　diatom　fluxes　is　identical　to　that　of　the　two　elements　dissolved　in　deep　seawater,　providing　further　evidence　for　the　dissolution　of　siliceous　matter　in　deep　water.　(C)　2011　Elsevier　Ltd.　All　rights　reserved.