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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

PETROGRAPHIC, GEOCHEMICAL, AND ISOTOPIC EVIDENCE OF CRUSTAL ASSIMILATION PROCESSES IN THE INDAIA-II KIMBERLITE, ALTO PARANAIBA PROVINCE, SOUTHEAST BRAZIL

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Author(s):
Lima, Nicholas M. [1] ; Azzone, Rogerio G. [1] ; Chmyz, Luanna [1] ; Guarino, Vincenza [2] ; Ruberti, Excelso [1] ; Silva, Simone [1] ; Svisero, Darcy P. [1]
Total Authors: 7
Affiliation:
[1] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508080 Sao Paulo - Brazil
[2] Univ Napoli Federico II, Dipartimento Sci Terra Ambiente & Risorse, Complesso Univ Monte St Angelo, Ed L, Via Cintia 26, I-80126 Naples - Italy
Total Affiliations: 2
Document type: Journal article
Source: CANADIAN MINERALOGIST; v. 58, n. 5, p. 563-585, SEP 2020.
Web of Science Citations: 0
Abstract

The Indaia-I and Indaia-II intrusions are hypabyssal. small-sized ultrabasic bodies belonging to the Cretaceous magmatism of the Alto Paranaiba Alkaline Province (southeast-central western Brazil). While Indaia-I is classified as an archetypal group-I kimberlite, Indaia-II (its satellite intrusion) presents several petrographic and chemical distinctions: (1) an ultrapotassic composition (similar to kamafugites), (2) lower volumes of olivine macrocrysts, (3) diopside as the main matrix phase (in contrast with the presence of monticellite in Indaia-D, (4) high amounts of phlogopite, and (5) abundant felsic boudinaged and stretched microenclaves and crustal xenoliths. Disequilibrium features, such as embayment and sieve textures in olivine and clinopyroxene grains, are indicative of open-system processes in Indaia-II. Mineral reactions observed in Indaia-II (e.g., diopside formed at the expense of monticellite and olivine; phlogopite nearby crustal enclaves and close to olivine macrocrysts) point to an increase in the silica activity of the kimberlite magma; otherwise partially melted crustal xenoliths present kalsilite, generated by desilification reactions. The high Contamination Index (2.12-2.25) and the large amounts of crustal xenoliths (most of them totally transformed or with evidence of partial melting) indicate a high degree of crustal assimilation in the Indaia-II intrusion. Calculated melts (after removal of olivine xeuocrysts) of Indaia-II have higher amounts of SiO2, Al2O3, K2O, slightly higher Rb/Sr ratios, lower Ce/Pb and Gd/Lu ratios, higher Sr-87/Sr-86, and lower Nd-143/Nd-144 than those calculated for Indaiit-1. Crustal contamination models were developed considering mixing between the calculated melts of Indaia-I and partial melts modeled from the granitoid country rocks. Mixing-model curves using major and trace elements and isotopic compositions are consistent with crustal assimilation processes with amounts of crustal contribution of ca. 30%. We conclude that (1) Indaii-II is representative of a highly contaminated kimberlitic intrusion, (2) this contamination occurred by the assimilation of anatectic melts from the main crustal country rocks of this area, and (3) Indaii-I and Indaii-II could have had the same parent melt, but with different degrees of crustal contamination. Our petrological model also indicates that Indaii-II is a satellite blind pipe linked to the main occurrence Indaia-I. (AU)

FAPESP's process: 12/06082-6 - The Paraná-Etendeka magmatic province in Brazil: temporal and petrologic relationships between the tholeiitic and alkaline magmatism and geodynamic implications
Grantee:Excelso Ruberti
Support Opportunities: Research Projects - Thematic Grants
FAPESP's process: 18/15731-4 - Elements mobility during fenitization processes: the carbonatite metasomatism in the Alto Paranaíba and Ponta Grossa Arch alkaline provinces
Grantee:Luanna Chmyz
Support Opportunities: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 17/03768-8 - Xenocryst and Antecryst compositional influence in basic to ultrabasic alkaline magmas
Grantee:Rogério Guitarrari Azzone
Support Opportunities: Regular Research Grants