{"id":3771,"date":"2020-04-18T08:39:54","date_gmt":"2020-04-18T08:39:54","guid":{"rendered":"http:\/\/caribbeanlithos.ub.edu\/?p=3771"},"modified":"2020-09-18T08:40:52","modified_gmt":"2020-09-18T08:40:52","slug":"2020-the-petrologic-nature-of-the-medellin-dunite-revisited-an-algebraic-approach-and-proposal-of-a-new-definition-of-the-geological-body","status":"publish","type":"post","link":"https:\/\/caribbeanlithos.ub.edu\/?p=3771","title":{"rendered":"2020: The Petrologic Nature of the \u201cMedell\u00edn Dunite\u201d Revisited: An Algebraic Approach and Proposal of a New Definition of the Geological Body"},"content":{"rendered":"\n<p><strong>The Petrologic Nature of the \u201cMedell\u00edn Dunite\u201d Revisited: An Algebraic Approach and Proposal of a New Definition of the Geological Body<\/strong><\/p>\n\n\n\n<p>Abstract<\/p>\n\n\n\n<p>The \u201cMedell\u00edn Dunite\u201d, the main ultramafic body of the Central Cordillera of Colombia, constitutes a fragment of oceanic lithospheric mantle formed at a back\u2013arc basin\/incipient arc scenario emplaced onto the western continental margin of Pangaea during Triassic time. This body has been classically, and is still considered, mainly of dunite composition. However, in spite of two subsequent metamorphic imprints that obscure the primary mantle mineralogical composition, there is petrographic and geo-chemical evidence that points to a harzburgitic nature of the unit. In order to overcome the petrographic effects of medium\u2013T metamorphism, metasomatism, and serpentini-zation, we analyzed published and new major\u2013element geochemical data by means of algebraic methods to approximate the mantle mineralogical composition of ultramafic rocks. The restored mantle mineralogy clearly indicates that the body is mainly of harz-burgitic composition, and therefore we propose that the term \u201cMedell\u00edn Dunite\u201d should no longer be applied to avoid terminological confusion. Furthermore, a phase\u2013relation approach in simple systems for the metamorphic evolution allows identifying the main reason for the contradictory terminology used so far: olivine is paragenetic (stable) with tremolite and talc during medium\u2013T (ca. 600 \u00b0C) metamorphic imprint undergone by the body. During this initial metamorphic event, characterized by full hydration (as opposed to the late\u2013stage serpentinization), mantle pyroxenes reacted out and medi-um\u2013T olivine formed while high\u2013T olivine persisted metastably as a likely consequence of moderate temperature and sluggish diffusion kinetics. On the other hand, we ana-lyze two likely geodynamic scenarios to provide a common context of metamorphism for the ultramafic body and associated metabasites (Aburr\u00e1 Ophiolite): (i) ocean\u2013floor metamorphism and (ii) intra\u2013backarc subduction\u2013initiation metamorphism. The latter allows a new tectonic view of the Aburr\u00e1 Ophiolite, formed by tectonic units from the upper and down going plates on a nascent active plate margin. For all these reasons, we propose the new term \u201cMedell\u00edn Metaharzburgitic Unit\u201d in order to combine in a single term the original high\u2013T mantle composition, its subsequent metamorphic transformation and the independent tectonic character of the ultramafic body.<\/p>\n\n\n\n<p><strong>Keywords:<\/strong> Medell\u00edn Dunite; Medell\u00edn Metaharzburgitic Unit; metaharzburgite; phase relations; ophiolite<\/p>\n\n\n\n<p>----------------------------------------------------------------------------------------------------------<\/p>\n\n\n\n<p><strong>To Cite this article:<\/strong>  Garcia\u2013Casco, A.; Restrepo, J.J.; Correa\u2013Mart\u00ednez, A.M.; Blanco\u2013Quintero, I.F.; Proenza, J.A.; Weber, M.; Butjosa, L. (2020). The petrologic nature of the \u201cMedell\u00edn Dunite\u201d revisited: An algebraic approach and proposal of a new definition of the geological body. In: G\u00f3mez, J. &amp; Pinilla\u2013Pachon, A.O. (editors), The Geology of Colombia, Volume 2 Mesozoic. Servicio Geol\u00f3gico Colombiano, Publicaciones Geol\u00f3gicas Especiales 36, 31 p. Bogot\u00e1.  <\/p>\n\n\n\n<p><strong>DOI<\/strong>:&nbsp;<a href=\"https:\/\/doi.org\/10.32685\/pub.esp.36.2019.02\">10.32685\/pub.esp.36.2019.02<\/a><\/p>\n\n\n<p><!--EndFragment--><\/p>","protected":false},"excerpt":{"rendered":"The Petrologic Nature of the \u201cMedell\u00edn Dunite\u201d Revisited: An Algebraic Approach and Proposal of a New Definition of the Geological Body Abstract The \u201cMedell\u00edn Dunite\u201d, the main ultramafic body of the Central Cordillera of Colombia, constitutes a fragment of oceanic lithospheric mantle formed at a back\u2013arc basin\/incipient arc scenario emplaced onto the western continental margin of Pangaea during Triassic time.&nbsp;<a href=\"https:\/\/caribbeanlithos.ub.edu\/?p=3771\" class=\"read-more\">Continue Reading<\/a>","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[130,41,44],"tags":[],"class_list":["post-3771","post","type-post","status-publish","format-standard","hentry","category-publications2020","category-colombia","category-publications","cat-130-id","cat-41-id","cat-44-id"],"_links":{"self":[{"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=\/wp\/v2\/posts\/3771","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3771"}],"version-history":[{"count":2,"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=\/wp\/v2\/posts\/3771\/revisions"}],"predecessor-version":[{"id":3775,"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=\/wp\/v2\/posts\/3771\/revisions\/3775"}],"wp:attachment":[{"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3771"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3771"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/caribbeanlithos.ub.edu\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3771"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}