First occurrence of kitagohaite, Pt<sub>7</sub>Cu. from the Quadrilátero Ferrífero, Brazil

Sampaio, Cristiano; Nalini Jr., Herminio Arias; Gonçalves, Cristiane Paula de Castro; Santos, Geraldo Magela; Alkmim, Ana Ramalho

doi:10.1590/0370-44672023770030

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Scientific Communication • REM, Int. Eng. J. 77 (1) • Jan-Mar 2024 • https://doi.org/10.1590/0370-44672023770030 copy

First occurrence of kitagohaite, Pt₇Cu. from the Quadrilátero Ferrífero, Brazil

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

A kitagohaite grain, measuring approximately 1.0 mm, was retrieved from an alluvial gold gravity concentrate from the southeastern Quadrilátero Ferrífero (QFe), Mariana, Brazil. The grain exhibits a cubic structure, whitish-steel-gray, and has a metallic luster. It is composed of Wt. 94.42% Pt and 5.56% Cu (n=9), yielding the empirical formula Pt_6.78Cu_1.22. This groundbreaking discovery marks the first documented occurrence of kitagohaite in South America. This hydrothermal deposition of kitagohaite indicates that its mineralization is constrained to temperatures <500º C, as inferred by the stability of synthetic Pt₇Cu.

Keywords:
kitagohaite; Pt Cu; platinum grain; jacutinga ; Quadrilátero Ferrífero

Element	Accel. Voltage	Probe Current	X-ray line	Peak Position	Reference Material	Wt.%
Pt	20 kV	40 nA	Ma	193.252mm	Pt-metal	99.999%
Cu	20 kV	40 nA	Ka	107.403mm	Cu-metal	99.998%

SEM (EDS)	n1	n2	n3	n4	n5	n6	n7	n8	n9	n10
Wt.%PT	94.9	94.3	94.1	93.9	94.1	94.7	94.5	95.2	93.3	94.0
Wt.%CU	5.7	5.7	5.7	5.6	5.8	5.9	5.8	5.7	5.5	5.6
Total %	100.6	100.0	99.8	99.5	99.9	100.6	100.3	100.9	98.8	99.6
EPMA (WDS)	n1	n2	n3	n4	n5	n6	n7	n8	n9	-
Wt.%PT	94.57	94.64	94.33	93.77	94.53	94.56	94.66	94.72	94.05	-
Wt.%CU	5.42	5.33	5.66	6.19	5.46	5.43	5.32	5.27	5.94	-
Wt. %Pd	<0.04	<0.04	<0.04	0.04	<0.04	<0.04	<0.04	<0.04	<0.04
Wt.% Total	99.99	99.97	99.99	100.0	99.99	99.99	99.98	99.99	99.99	-

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[1] 2 cristianossampaio@yahoo.com.br

Mineral	Theorical chemical formula	Theorical Wt% Pt	Theorical Wt% Cu
kitagohaite	Pt₇Cu	95.55	4.45
this work	Pt_6.78Cu_1.22^* * Empirical based on Wt.% results from EPMA(WDS).	94.42^* * Empirical based on Wt.% results from EPMA(WDS).	5.56^* * Empirical based on Wt.% results from EPMA(WDS).
orthocuproplatinum	Pt₃Cu	90.21	9.79
hongshiite	PtCu	75.43	24.57
tomamaeite	PtCu₃	50.58	49.42

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First occurrence of kitagohaite, Pt7Cu. from the Quadrilátero Ferrífero, Brazil

Abstract

First occurrence of kitagohaite, Pt₇Cu. from the Quadrilátero Ferrífero, Brazil