巴西中部Crixás绿岩带与科马铁矿相关的Boa Vista镍铜硫化物矿床:科马铁矿流相与勘探的认识

IF 1.7 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
Tiago Felipe Arruda Maia , César F. Ferreira-Filho , Saulo Batista de Oliveira
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引用次数: 0

摘要

Boa Vista镍铜矿床是与贫铝科马铁矿(ADK)相关的新太古代矿化的罕见例子。博阿维斯塔矿床的新数据,包括地质和岩石学描述,以及地球化学和同位素结果的科马铁矿和硫化物矿石,被整合到这项研究中,以提高对其起源相关过程的理解。虽然矿床和寄主岩受到构造作用和绿片岩-角闪岩相变质作用的影响,但整个绿岩带的原始岩浆结构和成分都得到了不同程度的保存。研究结果表明,Boa Vista矿床为未分异的橄榄石堆积河道化/管状流相单元,上覆玄武岩和玄武岩科马岩流,与含硫化物的石墨片岩夹层。Boa Vista矿床是一种I型(基底/接触)科马铁矿伴生镍铜(PGE)矿床,其沿剪切带被破坏程度不同。主矿体以含镍黄铁矿、磁黄铁矿和少量黄铜矿的基质矿角砾岩为主,锌含量高。岩石地球化学、AFC模型、矿石地球化学和硫同位素数据支持石墨片岩对马马岩浆岩的地壳污染。Ni-Cu矿石的δ34S同位素值在+16 ~ +19之间,这是由于母岩中含有δ34S值在+30 ~ +34之间的硫化物的石墨片岩污染了母岩岩浆。矿石品位相对较低是由于金属含量相对较低,与计算出的岩浆与硫化物比(R因子)在300 ~ 400之间一致。高Ni-MgO-Zn含量可作为寻找巴西中部科马铁矿伴生Ni-Cu-(PGE)硫化物矿床新目标的地球化学找矿标志。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
The komatiite-associated Boa Vista Ni-Cu sulfide deposit, Crixás greenstone belt, Central Brazil: Insights into komatiite flow facies and exploration
The Boa Vista Ni-Cu deposit is an uncommon example of Neoarchean mineralization associated with aluminum-depleted komatiite (ADK). New data for the Boa Vista deposit, including geological and petrographic descriptions, as well as geochemical and isotopic results for komatiites and sulfide ore, are integrated into this study to improve the understanding of the processes associated with its origin. Although the deposit and host rocks were affected by tectonism and greenschist to amphibolite facies metamorphism, primary magmatic textures and compositions are variably preserved throughout the greenstone belt. Our results show that the Boa Vista deposit is hosted by an undifferentiated olivine cumulate channelized/conduit flow facies unit overlying flows of basalts and basaltic komatiites interlayered with sulfide-bearing graphite schist. The Boa Vista deposit is a Type I (basal/contact) of the komatiite-associated Ni-Cu-(PGE) deposit that was variably disrupted along shear zones. The main orebody consists predominantly of matrix ore breccia consisting of pentlandite, pyrrhotite, and minor chalcopyrite and has high Zn contents. Lithogeochemistry, AFC model, ore geochemistry, and sulfur isotopic data support crustal contamination of the komatiitic magma by graphite schist. Strongly positive δ34S isotopic values for the Ni-Cu ore, ranging from +16 to +19, are modeled as resulting from contamination of the komatiitic magma with host graphite schist that contains sulfides with δ34S values ranging from +30 to +34. The relatively low grades of the ores are attributable to relatively low metal tenors, consistent with a magma: sulfide ratio (R factor) calculated between 300 and 400. High Ni-MgO-Zn content can be a geochemical exploration criteria guide to finding new targets for komatiite-associated Ni-Cu-(PGE) sulfide deposits in central Brazil.
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来源期刊
Journal of South American Earth Sciences
Journal of South American Earth Sciences 地学-地球科学综合
CiteScore
3.70
自引率
22.20%
发文量
364
审稿时长
6-12 weeks
期刊介绍: Papers must have a regional appeal and should present work of more than local significance. Research papers dealing with the regional geology of South American cratons and mobile belts, within the following research fields: -Economic geology, metallogenesis and hydrocarbon genesis and reservoirs. -Geophysics, geochemistry, volcanology, igneous and metamorphic petrology. -Tectonics, neo- and seismotectonics and geodynamic modeling. -Geomorphology, geological hazards, environmental geology, climate change in America and Antarctica, and soil research. -Stratigraphy, sedimentology, structure and basin evolution. -Paleontology, paleoecology, paleoclimatology and Quaternary geology. New developments in already established regional projects and new initiatives dealing with the geology of the continent will be summarized and presented on a regular basis. Short notes, discussions, book reviews and conference and workshop reports will also be included when relevant.
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