Evaporite formation during weathering of Antarctic meteorites––A weathering census analysis based on the ANSMET database

摘要: Abstrac tÐ Weather ing of meteorit es at the scale entir e Anta rctic Search for M eteoritesprogram populati on is studi ed by analyzi ng recen t version online rcticmeteorit class iÞcat ion databas that includes informat about 15,263 meteo rites. Thi spaper upda tes, supplem ents, and expan ds last Antarcti c rite weatheri cen susby Vel bel (1988, eteoritics 23:151 Ð159). On average 5% all mete orites areindicated as evap orite bearing in eteorite Data base. Eva porit formati ondepends composi tional group . porites are much more common C ch ondrites thanon ordinar y chon drites, supporti previous Þndings. Ordi nary chond rites petrologic type3 often have evapori tes their surface than other petrolo gic types.Contrary to Þndin gs, there no ap parent relation betw een evapo form ationand rustiness. Some orite-bear Þelds ins uence frequency te-mineral ation orites. The insuence locat apparent ly related todifferences en vironmen tal co nditions, most prob ably micro climate or Uan d hyd rologiccondition s. Ther n o between abundan ce te-be aring anddistance from sea. Evap varies with year collec tion; howeve r, it wasnot pos sible distinguis h wheth er this ann ual anges r anartifact sampl categorizat curati on.INTR ODUC TIONTwo main types products onAnta visible hand-sam plescale : rust tes. Alt hough many scient iÞcpapers discus sed problem s ofAnta (e.g., Gooding 1981, 1986; Velbeland Go oding 1990; Harve Sco re 19 91; ittlefehldtand Lindstr om 1991; Benoi Sears 1999; Croz azet al. 2003; Lee Blan 2004; Tyr a et 2007), onlya few artic les be publis hed abou oriticprodu cts arvin 1980;Jull 1988; Velbel Gounell eand Zolen sky 2001).Eva highly water solubl miner als,form result evaporat freezing ofbodies water. Annual air tempe ratures inAnta ice below 0 !C(Comis 2000). How ever, insol heati thegeneral dark lored usu ally fusi on-crus tedmete during wi nd-free summ da ys pro ducescond itions beneath exposed surfa ces under whi chliquid can ex ist (Schu ltz 1986 , y2003). Capill ary thin Þlms unfrozen watercan also oc cur (e.g ., Campbell an dClaridg 1987). Som etimes amount wat besigniÞ cant; exampl Cassidy (2003) repo rted largemeltw ater pond area Lewi liff (LEW)mete Þeld (alth ough was frozen duringthe tim f pedition). In additio n, somemete found shallo w dep ressions Þlled withrefro zen (Goodi Harvey 200 3). Based the44 3