The Jabali nonsulfide Zn–Pb–Ag deposit, western Yemen

Mondillo, Nicola; Boni, Maria; Balassone, Giuseppina; Joachimski, Michael M.; Mormone, Angela

doi:10.1016/j.oregeorev.2014.02.003

Cited by 28 publications

(43 citation statements)

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“…Oxygen isotope values were corrected using the phosphoric acid fractionation factors given by Kim et al (2007) for calcite and Gilg et al (2003) for smithsonite and cerussite. As the phosphoric acid fractionation factor for hydrozincite has not been determined yet, we adopted the smithsonite acid fractionation factor (Gilg et al 2003) as in earlier studies (e.g., Mondillo et al 2014;Arfè et al 2017Arfè et al , 2018.…”

Section: Methodsmentioning

confidence: 99%

“…Concretionary calcite was precipitated after all the mentioned phases, occurring in the nonsulfide mineralization as final cavity-filling precipitate. From a genetic point of view, it is relevant that the oxidized Zn and Pb minerals mainly formed at direct expense of the sulfides, with a very small amount of nonsulfide ores showing wall-rock replacement features, e.g., Zn-bearing illite that likely formed by progressive "zincitization" of a preexisting Zn-barren illite (see for example Mondillo et al 2014). These facts suggest that the Zn-Pb-bearing solutions deriving from sulfide alteration were quickly neutralized by the carbonate environment, and did not migrate for long distances through the fractures of the host rock.…”

Section: Nonsulfide Genesis Nature Of the Fluids And Relationships mentioning

confidence: 99%

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From Alpine-type sulfides to nonsulfides in the Gorno Zn project (Bergamo, Italy)

et al. 2019

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Recent exploration of the Gorno Zn-Pb-Ag deposit in northern Italy identified 3.3 Mt of sulfides at 4.9% Zn, 1.3% Pb, and 27.2 g/ t Ag (indicated+inferred resources), and a further mineralized nucleus of mixed sulfides-nonsulfides in the Val Vedra area, currently under evaluation. The ores are hosted in Triassic limestone and shale. Sulfides (sphalerite, Ag-bearing galena, minor pyrite, and chalcopyrite) paragenetically follow Mn-Fe-bearing saddle dolomite and sparry calcite. The mineral association, and the carbon and oxygen isotope ratios of the sparry calcite (avg. δ 13 C = 1.0 ± 0.6‰ V-PDB; avg. δ 18 O = 19.63 ± 1.25‰ V-SMOW), are in agreement with precipitation from hydrothermal fluids in a deep burial setting. Sulfide emplacement occurred before the Alpine orogeny, likely during the Early-Middle Jurassic, in analogy to other Alpine-type deposits. The nonsulfide ore formed at the expense of sulfides, and mainly consists of smithsonite, hydrozincite, hemimorphite, and cerussite. The C-Oisotope values of the early generations of Zn-carbonates are characterized by δ 18 O between 24.1 and 26.8‰ V-SMOW and δ 13 C ratios between − 3.1 and 1.7‰ V-PDB. The later generations have lower δ 18 O (21.9 to 23.9‰) and lower δ 13 C (− 6.2 to − 3.9‰). These compositions, as those measured on cerussite (δ 13 C = −6.3 and − 7.7‰; δ 18 O = 14.0 and 15.3‰), agree with the formation of the nonsulfides in a supergene environment, under climatic conditions warmer than today. The δ 18 O decrease from early to late generations suggests progressive involvement of meteoric water sourced from higher altitudes. These characteristics indicate that the nonsulfides formed during the exhumation of the Gorno area from Miocene to Pliocene.

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Section: Methodsmentioning

confidence: 99%

Section: Nonsulfide Genesis Nature Of the Fluids And Relationships mentioning

confidence: 99%

From Alpine-type sulfides to nonsulfides in the Gorno Zn project (Bergamo, Italy)

et al. 2019

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“…The Jabali mixed sulfide-nonsulfide Zn mineralization is located about 110 km east of Sana'a (Yemen) (Mondillo et al, 2014a). The host rocks of both ore types are intensively dolomitized Jurassic carbonates.…”

Section: Yemenmentioning

confidence: 99%

A global assessment of Zn isotope fractionation in secondary Zn minerals from sulfide and non-sulfide ore deposits and model for fractionation control

et al. 2018

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“…Calcium reprecipitated in the supergene zone as calcite and gypsum; Mg was partly trapped into smithsonite (Mg 2+ and Zn 2+ have a very similar ionic radius). This partial-replacement phenomenon has been well documented in the Jabali (Yemen) and Sardinia (Italy) nonsulfi de deposits (Boni et al, 2013;Mondillo et al, 2014).…”

Section: Discussionmentioning

confidence: 71%

“…The isotope values of supergene smithsonites reported in literature show a much wider range and are signifi cantly depleted in 13 C (from 0‰ to -12‰). This large range in δ 13 C suggests different carbon sources, with high δ 13 C values indicating a contribution of inorganic carbon from the host-rock carbonates, whereas low δ 13 C values can be explained by the addition of isotopically light soil-gas CO 2 (Gilg et al, 2008, and references therein;Coppola et al, 2009;Mondillo et al, 2014). At Reef Ridge, negative δ 13 C values for smithsonite occur in only two samples.…”

Section: Discussionmentioning

confidence: 99%

A cold supergene zinc deposit in Alaska: The Reef Ridge case

Santoro

Boni

Mondillo

et al. 2015

Geological Society of America Bulletin

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The Reef Ridge deposit is a typical supergene "nonsulfi de" zinc mineralization, located in the Yukon-Koyukuk region of west-central Alaska (USA). It is hosted in sedimentary rocks of the Farewell terrane, a continental fragment sandwiched between the Siberian and Laurentian cratons during the early Paleozoic. The mineralization occurs in Lower-Middle Devonian shallowwater dolomite of a Paleozoic carbonate platform succession belonging to the Nixon Fork tectonic unit. The mineralization consists of oxidized minerals associated with minor remaining sulfi des (pyrite/marcasite and sphalerite). In the oxidation zone, smithsonite is the predominant mineral, mixed with Fe-(hydr)oxides (goethite and hematite).A complete petrographic and mineralogical study was performed. Samples were analyzed by X-ray diffraction, inductively coupled plasma-mass spectrometry and emission spectrometry, energy dispersive scanning electron microscopy, and QEMSCAN ® (quantitative evaluation of minerals by scanning electron microscopy). The most abundant mineral in the nonsulfi de ore is smithsonite. Similar to other nonsulfi de Zn deposits worldwide, the fi rst generation of smithsonite has replaced both primary sphalerite and the host carbonates. A second smithsonite generation precipitated as cement in vugs, cavities, and fractures. Minor zinc amounts also occur in the Fe-(hydr) oxides , and zinc traces have been identifi ed in clay minerals.The carbon and oxygen isotope values of smithsonite at Reef Ridge vary from -0.7 to 2.1‰ relative to Vienna Peedee belemnite (VPDB) and 19.1‰ to 21.9‰ relative to Vienna standard mean ocean water (VSMOW ). The δ 13 C values are similar to those of the host rock, suggesting that the predominant carbon source for smithsonite was the host carbonates, with only a limited contribution from organic carbon. The oxygen isotope ratios of Reef Ridge smithsonite are more depleted in 18 O compared to supergene nonsulfi des from other parts of the world formed under warm-humid, temperate, or semiarid climates. The oxygen isotope fractionation between water and smithsonite, which relates the δ 18 O value of the mineralizing solution, the formation temperature of smithsonite, and its δ 18 O composition, indicates that the δ 18 O composition of Reef Ridge smithsonite is related to very low formation temperatures (~10 °C), and strong depletion in 18 O of the precipitating waters.The δ 18 O smithsonite composition, the strong 18 O depletion, and the relationship of the formation of the Reef Ridge nonsulfi de deposit with the development of the Sleetmute upland surface (which started in the Late Tertiary and continues to the present) indicate that the formation of the Reef Ridge nonsulfi de deposit is probably related to cold/humid weathering episodes during a period comprised between Late Tertiary and Holocene.The "traditional" interpretation on the genesis of Zn nonsulfi de deposits in warmhumid, temperate, or semiarid conditions should be questioned where other climate zones are indicated.

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The Jabali nonsulfide Zn–Pb–Ag deposit, western Yemen

Cited by 28 publications

References 48 publications

From Alpine-type sulfides to nonsulfides in the Gorno Zn project (Bergamo, Italy)

From Alpine-type sulfides to nonsulfides in the Gorno Zn project (Bergamo, Italy)

A global assessment of Zn isotope fractionation in secondary Zn minerals from sulfide and non-sulfide ore deposits and model for fractionation control

A cold supergene zinc deposit in Alaska: The Reef Ridge case

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