Produção Nacional
QUÍMICA MINERAL DAS ROCHAS VULCÂNICAS DA PENÍNSULA FILDES (ILHA REI GEORGE), ANTÁRTICA
2001; Sociedade Brasileira de Geologia; Volume: 31; Issue: 3 Linguagem: Inglês
10.25249/0375-7536.2001313299306
ISSN2177-4382
AutoresAdriane Machado, Evandro Fernandes de Lima, Farid Chemale, Joaquim Daniel de Liz, J Avila,
Tópico(s)Isotope Analysis in Ecology
ResumoTART IC Studies realized in the Fildes Pen insula (so uthwest King George Island.Autmtic) pcnn ucd lhe iden tification of volcan ic rock s succession from basic to irucnncdiar c composition.Dacites and rhyolites arc rare.The age o f these rocks vary from Paleoce ne to Eoce ne.Geoc he mistry studies indi cate these roc ks arc rich in A I ,O ~.Rb.Hu, Sr and they presen t e nric hmc nt in LRE E rclmi vc to II REE .II is ty pica l of high -A I vo lca nic asso ciat ion with calc-al kalin e a ffini ty".It is evi nced fo r Alkal i Index x AI,O l diagram .The Ni. C r. Co .l'I lgO co ntents of ba sic roc ks arc lower than pri mary composi tions and it discloses that these magmas arc e volve d: lOSr/ 1l6 Sr initia l ratio s arc 0.703 3 10 0.7037 and I.HNd/ l-l-lNd arc 0.5 12959 100.512967.TIle values of eNd (I = 55 Ma ) range betw een + 6.52 and + 6.72 .Th e Isotopic and Geoch emi stry data suggest that the rock s were generated from partial mel ting of lith osph eri c man tle in an isla nd arc e nvironment.Fildes Pe ninsu la volcan ic rock s pre sent porphyrit ic, glomcropo rphyritic .uuc rgmnular and irucrscrtal text urcs.Mineral che mistry indicates typical compositon of low-K and calc-alkaline ser ies of island arcs.Plag iocla se com positions ere mostly anort hite a nd bytownite in the basic rock s and mostly bytownite in the intermediat e roc ks.Plagioclase matrix is Jnbradontc.Aug ite is the ma in mafi c phase ( WO ~~_ l7' En/ l _ St • Fsl.:.l-~~) in the basic roc ks.The pyroxene com position (Wo 3 1l' ~n~~.Fs 17 ) in the ba~alti c ande sites is si milar 10 basalt s. ~i getln i te (\\'6 11-1~' ~11 ~;.f'I" I•S~:l.l. ) is u!lUs uall~h;lse and.it i ~only present s in !he ma[rIx. of basalts.l~ronzllc ( W~)J.: En 71l • FS 26 " .7) Ol.:c.urs as ml l.:rophc lH~crysl lll two sa!nplcs 01\)~lsall IC ando.:.s lh:S.O h "!l1": I ~common phase III the baSIC rod s and I[ sbwos cnsot llc ccmposlfion. 1 he opaq ue phase I S repres ente d lor magncntc.[I contams ulvospiuc l from 16 [ 0 25 '70 .Gcorhc nnobaromctry o f clin opyroxc nc -onbcpyroxcnc from basalt ic andesi te (AF-2 1) was obtained by Ca-QU ILr:" Program.It yie lded a crys tallization and cquili brutionrcrupcrat urc bel wee n I0 65"C 10 I070"C for pressure s from I ba r 10 ISOO hal'.The ev aluation of Minera l Chem istry.Litho chcmi stry a nd Isotopic co mpo stions a rc according 10 hypot hesis of fructicnn l cry stalliz.uionfor e volu tio n o f Filde s Pe ninsula volcanic rods, It was not fo und e vidences for interference of other petro gen etic processes.Keywo rds: basalt s. mine
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