The use of mineral interfaces in sand-sized volcanic rock fragments to infer mechanical durability  

作　　者：Emilia Le Pera Consuele Morrone 

机构地区：[1]Dipartimento di Biologia,Ecologia e Scienze della Terra(DiBEST),Universita

出　　处：《Journal of Palaeogeography》2020年第3期288-313,共26页古地理学报（英文版）

基　　金：funded by MIUR (Ministero dell’Istruzione,dell’Università e della Ricerca),ex 60% fund (2019 year) to E. Le Pera。

摘　　要：The use of mineral interfaces, in sand-sized rock fragments, to infer the influence exerted by mechanical durability on the generation of siliciclastic sediments, has been determined for plutoniclastic sand. Conversely, for volcaniclastic sand, it has received much less attention, and, to our knowledge, this is the first attempt to make use of the volcaniclastic interfacial modal mineralogy of epiclastic sandy fragments, to infer mechanical durability control at a modern beach environment. Volcaniclastic sand was collected along five beaches developed on five islands, of the southern Tyrrhenian Sea(Alicudi, Filicudi, Salina, Panarea and Stromboli) from the Aeolian Archipelago, and one sample was collected near the Stromboli Island volcanic crater. Each sample was sieved and thin sectioned for petrographic analysis. The modal mineralogy of the very coarse, coarse and medium sand fractions was determined by point-counting of the interfacial boundaries discriminating 36 types of interfaces categories, both no-isomineralic and/or no iso-structural(e.g., phenocrystal/glassy groundmass or phenocrystal/microlitic groundmass boundaries) and iso-mineralic interfaces, inside volcanic lithic grains with lathwork and porphyric textures. A total of 47,386 interfacial boundaries have been counted and, the most representative series of interfaces, from the highest to the lowest preservation, can be grouped as: a) ultrastable interfaces, categorized as Pl(Plagioclase)/Glgr(Glassy groundmass) > > Px(Pyroxene)/Glgr > > Ol(Olivine)/Glgr > > Op(Opaque)/Glgr > > Hbl(Hornblende)/Glgr> > Bt(Biotite)/Glgr > > Idd(Iddingsite)/Glgr > > Rt(Rutile)/Glgr;b) stable interfaces, categorized as Pl/Migr(Microlitic groundmass) > > Op/Migr > > Px/Migr > > Ol/Migr;c) moderately stable interfaces, categorized as Op/Px > > Op/Hbl > > Px/P > > Ol/Pl> > Bt/Op;and d) unstable interfaces, categorized as Pl/Pl > > Px/Px > > Ol/Ol > >Op/Op > > Hbl/Hbl > > Bt/Bt. Grains, eroded from the volcanic bedrock, if affected solely by abrasion, developed a rounded an

关 键 词：Volcaniclastic sand Mineral interfaces Volcanic beach environment Mechanical durability 

分 类 号：P57[天文地球—矿物学]