Nova Terra 52

Abstract In the Iberian Massif, the Ossa-Morena Complex and its prolongation in the NW Iberia allochthonous complexes represent the outermost section of the North African margin of Gondwana. This margin hosted a long-lived mag- matic arc active at least between c. 750 to 500 Ma. The activity of this arc can be traced by sedimentary sequences deposited along the margin and igneous rocks generated during the arc construction, as well as by deposits generated during its progressive dismantling. The dynamic evolution of the peri-Gondwanan North-African margin from the /DWH (GLDFDUDQ WR WKH (DUO\ &DPEULDQ UHVXOWHG LQ D FRPSOH[ WHFWRQLF FRQ¿JXUDWLRQ LQYROYLQJ XQLWV ZLWK FRQWLQHQWDO D൶QLW\ DQG RWKHUV RI RFHDQLF WUDQVLWLRQDO QDWXUH 7KLV 3K' 7KHVLV SUHVHQWV WKH UHVXOWV REWDLQHG IURP WKH VWXG\ RI this margin section preserved in SW Iberia and suggests a possible geodynamic and petrogenetic model based on its geochemical and isotopic evolution. This peri-Gondwanan arc section is probably one of the best well-preserved in WKH 9DULVFDQ 2URJHQ 7KH UHVXOWV DOVR LQFOXGH WKH LGHQWL¿FDWLRQ RI SUHYLRXVO\ XQGHVFULEHG WHFWRQRVWUDWLJUDSKLF XQLWV and the detailed description of a new ophiolitic unit, the Mérida Ophiolite. The methodology used includes a structural study of the units implied in this section, whole-rock and isotopic (Sr- Nd) geochemistry, and geochronology (U-Pb ) of implied rocks. The study of the Merida ophiolite further included Hf isotopes in the analyzed zircons. The results have been published in journals of impact in Earth Sciences. In this sense, this volume is presented as a compilation of publications following a chronological and thematic order. 7KH ¿UVW DQG VHFRQG SDSHUV GHVFULEH WKH JHRFKHPLFDO IHDWXUHV RI WKH PHWDVHGLPHQWDU\ EDVHPHQW RI WKH 2VVD 0R - rena Complex. The Ediacaran Serie Negra is compared with equivalent series in the Central Iberian Zone, concluding that both were originally deposited in distant domains along the Gondwana margin. In contrast, Montemolín and Tentudía formations, which compose the Serie Negra, share isotopic signatures with the Ediacaran metasedimentary sequences preserved in the Saxo-Thuringian Zone of the Bohemian Massif, suggesting sedimentation in a roughly similar location of both facing the West African Craton. The third article gathers the results achieved from the Mérida Massif mapping based on tectonostratigraphic cri- WHULD ,Q WKLV VHQVH WKH GDWD REWDLQHG DOORZHG WR GLVWLQJXLVK WKUHH XQLWV RI GL൵HUHQWLDWHG D൶QLW\ DQG WHFWRQRWKHUPDO HYROXWLRQ $ /RZHU 8QLW RI FRQWLQHQWDO QDWXUH DQ ,QWHUPHGLDWH 8QLW ZLWK RFHDQLF WUDQVLWLRQDO D൶QLW\ WKDW GH¿QHV WKH Merida Ophiolite, and an Upper Unit of continental nature represents an axial section of the peri-Gondwanan arc. The Upper Unit description was addressed in the fourth paper. Petrogenetic and geodynamic evolution of the Ediacaran peri-Gondwanan arc section was proposed based on the geochemical, isotopic, and geochronological fea- WXUHV RI WKH SUHVHUYHG LJQHRXV PDWHULDOV 7KLV UHVHDUFK KDV UHYHDOHG WKH VLJQL¿FDQW UROH SOD\HG E\ VXEGXFWLRQ HURVLRQ processes and allowed to recognize a cyclical magmatism pattern during the period c. 602 - 541 Ma, driven by slab- mantle-upper plate interaction. 7KH ¿IWK SDSHU LV D PDQXVFULSW XQGHU UHYLHZ 7KLV UHVHDUFK SURYLGHV D FRPSOHWH VWXG\ RI WKH JHRFKHPLVWU\ LVRWR - pic sources, geochronology, and tectonometamorphic evolution of the Mérida Ophiolite. This Ophiolite has been in- terpreted as the oceanic lithosphere of a back-arc basin, opened around c.600-590 Ma, and subsequently experienced SURJUDGH PHWDPRUSKLVP ZLWK DQ HVWLPDWHG SHDN DW F & DQG NEDU In order to complete the dynamic and geochemical evolution of the preserved peri-Gondwanan arc section, we KDYH DOVR LQFOXGHG D FKDSWHU GHVFULELQJ WKH ¿QDO VWDJH RI DUF GLVPDQWOLQJ DQG FROODSVH GXULQJ WKH (DUO\ &DPEULDQ 7KH features of the deposited volcano-sedimentary sequence and associated magmatism indicate an increasingly alkaline WUHQG DQG VXJJHVW VLJQL¿FDQW FKDQJHV LQ WKH PDUJLQ G\QDPLFV WRZDUGV D WHFWRQLF VHWWLQJ ZKHUH WKH H[WHQVLRQ ZRXOG dominate. Previous works performed in this Iberian domain had addressed separately aspects related mainly to the tectonic VHWWLQJ DQG SHWURORJ\ RI WKH URFNV LQFOXGHG LQ WKLV *RQGZDQD PDUJLQ VHFWLRQ )RU WKH ¿UVW WLPH WKH ZRUNV JDWKHUHG LQ