Volcanoes morphology of the North Harghita (Romania) Volcanic chain segment : similarities and differences
Authors: Mirea Viorel , Seghedi Ioan 
Published: March 2020

&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;&lt;span&gt;Using numerical reconstructions of the morphology of the volcanoes in correlation with petrography, paleomagnetic and K-Ar age data we are showing the differences in eruptive activity between volcanoes in a post-collisional setting. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;North Harghita is a chain segment of the Ca&amp;#774;limani-Gurghiu-Harghita(Romania) volcanic range, composing by row of volcanic of partial overlapping edifices. It is formed from north to south by the following volcanic edifices: R&amp;#259;chi&amp;#539;i&amp;#537; (small monogenetic aphanitic dacitic shield volcano) and the Ostoro&amp;#537;, Ivo-Cocoiza&amp;#537;, V&amp;#226;rghi&amp;#537; (including Harghita B&amp;#259;i) andesitic (dacitic) composite volcanoes. &lt;/span&gt;&lt;/p&gt;&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;The Miocene-Pliocene calc-alkaline volcanism developed in the North Harghita Mts. for ca. 2.4 Ma (6.3-3.9 Ma). The R&amp;#259;chi&amp;#539;i&amp;#537; monogenetic volcano has been generated at ~ 5.8 Ma. The volcanic edifices of Ostoro&amp;#537; and Ivo-Cocoiza&amp;#537; were build up in the same time interval (6.3-5.0 Ma), lasting ~1.5 Ma each; V&amp;#226;rghi&amp;#537; main edifice indicate a &lt;1 Ma-long activity (5.5-4.8 Ma), however dated debris avalanche suggest longer duration. &lt;/span&gt;&lt;/p&gt;&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;The Ostoro&amp;#537; and Ivo-Cocoiza&amp;#537; volcanic edifices after the build-up stage were followed by destructive east-oriented debris avalanches events (~ synchronous) and eruption activity stopped.&lt;/span&gt;&lt;/p&gt;&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;The V&amp;#226;rghi&amp;#537; edifice complex (including Harghita B&amp;#259;i volcano), experienced an intense build up stage followed by a south-west-oriented debris avalanche failure event. The southernmost Rupea basaltic andesite mega-block is 6.8 Ma old and can be attributed to the V&amp;#226;rghi&amp;#351; volcano suggesting a much longer duration for the volcano lifespan; later at 3.9 Ma a small effusive event was generated in the failure crater.&lt;/span&gt;&lt;/p&gt;&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;DEM volume calculations include present exposed edifices and debris avalanches. R&amp;#259;chi&amp;#539;i&amp;#537; is only of 0.8 &lt;/span&gt;&lt;span&gt;&lt;span&gt;km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;; &lt;/span&gt;&lt;span&gt;&lt;span&gt;Ostoro&amp;#537; volcano edifice have 16 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt; and a debris avalanche deposits of 6.1 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt; suggesting a total volumes of 22.1 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt;; Ivo-Cocoiza&amp;#537; volcano has 18.6 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt; and its debris avalanche deposits is of 12.6 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt;, suggesting a total volume of 31.2 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt;; V&amp;#226;rghi&amp;#537; volcano, the southernmost, has the largest volume of 84.9 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt; (111.7 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt; including Harghita B&amp;#259;i associated edifice) with a total debris avalanche deposits of 8.7 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt; with a total volume of 120.4 km&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;3&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt;.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;East-oriented debris avalanches of Ostoro&amp;#537; and Ivo-Cocoiza&amp;#537; travelled up to 20km where has been blocked by a higher morphology. South-west-oriented V&amp;#226;rghi&amp;#537; debris avalanche traveled up to 55km on a lower morphology, and it is much thinner. &lt;/span&gt;&lt;/p&gt;&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;The North-South-directed spatio-temporal evolution of North Harghita volcanic edifices reflect the southward propagation of strike-slip and normal faulting, following the post-collisional events in the East Carpathians. &lt;/span&gt;&lt;/p&gt;&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;Acknowledgements: This work was supported by a grant of the Ministry of Education and Scientific Research, CNCS-UEFISCDI, project number PN-II-IDPCE-2012-4-0137 and by grant of Ministry of Research and Innovation, CNCS&amp;#8211;UEFISCDI, project number PN-III-P4-ID-PCCF-2016-4-0014, within PNCDI III.&lt;/span&gt;&lt;/p&gt;