{"id":8163,"date":"2016-03-23T09:29:34","date_gmt":"2016-03-23T08:29:34","guid":{"rendered":"http:\/\/karmaka.de\/?p=8163"},"modified":"2016-03-23T09:29:34","modified_gmt":"2016-03-23T08:29:34","slug":"multiple-precursors-of-secondary-mineralogical-assemblages-in-cm-chondrites","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=8163","title":{"rendered":"Multiple precursors of secondary mineralogical assemblages in CM chondrites."},"content":{"rendered":"<p>Pignatelli, I., Marrocchi, Y., Vacher, Lionel. G., Delon, R. and Gounelle, M.<\/p>\n<p>Meteoritics &#038; Planetary Science. doi: 10.1111\/maps.12625<\/p>\n<p><a href=\"http:\/\/onlinelibrary.wiley.com\/doi\/10.1111\/maps.12625\/abstract\" target=\"_blank\"><strong>LINK<\/strong><\/a><\/p>\n<p>&#8220;We report a petrographic and mineralogical survey of tochilinite\/cronstedtite intergrowths (TCIs) in Paris, a new CM chondrite considered to be the least altered CM identified to date. Our results indicate that type-I TCIs consist of compact tochilinite\/cronstedtite rims surrounding Fe-Ni metal beads, thus confirming kamacite as the precursor of type-I TCIs. In contrast, type-II TCIs are characterized by complex compositional zoning composed of three different Fe-bearing secondary minerals: from the outside inwards, tochilinite, cronstedtite, and amakinite. Type-II TCIs present well-developed faces that allow a detailed morphological analysis to be performed in order to identify the precursors. The results demonstrate that type-II TCIs formed by pseudomorphism of the anhydrous silicates, olivine, and pyroxene. Hence, there is no apparent genetic relationship between type-I and type-II TCIs. In addition, the complex chemical zoning observed within type-II TCIs suggests that the alteration conditions evolved dramatically over time. At least three stages of alteration can be proposed, characterized by alteration fluids with varying compositions (1) Fe- and S-rich fluids; (2) S-poor and Fe- and Si-rich fluids; and (3) S- and Si-poor, Fe-rich fluids. The presence of unaltered silicates in close association with euhedral type-II TCIs suggests the existence of microenvironments during the first alteration stages of CM chondrites. In addition, the absence of Mg-bearing secondary minerals in Paris TCIs suggests that the Mg content increases during the course of alteration.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Pignatelli, I., Marrocchi, Y., Vacher, Lionel. G., Delon, R. and Gounelle, M. Meteoritics &#038; Planetary Science. doi: 10.1111\/maps.12625 LINK &#8220;We report a petrographic and mineralogical survey of tochilinite\/cronstedtite intergrowths (TCIs) in Paris, a new CM&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[61,9,18,60],"tags":[105,304,2637,2638],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/8163"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8163"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/8163\/revisions"}],"predecessor-version":[{"id":8164,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/8163\/revisions\/8164"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8163"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8163"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8163"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}