Origin of the Breno and Esino dolomites in the western Southern Alps (Italy): Implications for a volcanic influence

Hou, Yong; Azmy, Karem; Berra, Fabrizio; Jadoul, Flavio; Blamey, Nigel; Gleeson, Sarah A.; Brand, Uwe

doi:10.1016/j.marpetgeo.2015.10.010

Cited by 30 publications

(29 citation statements)

References 77 publications

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“…The latest saddle dolomite DC generation is limited to filling vugs and late fractures (Fig. G) that cut through all earlier dolomite phases, which implies formation at the deepest diagenetic settings during progressive burial (Hou et al ., ), and this is also consistent with the high mean Th value (100 °C). Sometimes, a dolomite vein is cut by calcite veins (Fig.…”

Section: Discussionsupporting

confidence: 87%

“…The near micritic grain size (5–50 µm) fabric‐retention, subhedral ‐ euhedral (planar‐s) crystal habit and non to dull CL exhibited by RD1 has been documented for numerous case examples in the literature and is most often attributed to early dolomitization of lime mud in a shallow burial setting at near‐ surface, low temperature conditions, although such textures do occur occasionally in dolomites formed at elevated temperatures (Sibley and Gregg, ; Al‐Aasm and Packard, ; Qian and You, , Hou et al ., ). The large surface areas of carbonate mud, which increase the nucleation rate compared with the growth rate, led possibly to the precipitation of this fine crystalline dolomite (Sibley and Gregg, ).…”

Section: Discussionmentioning

confidence: 97%

“…The undulose extinction in RD4 and RD5 provides evidence of distorted crystal lattice caused by crystal growth at high temperatures (>60 °C) of deep burial settings (e.g. Warren, ; Hou et al ., ). Cross‐cutting relationships between RD4 and RD5 and the other replacement dolomites are not observed.…”

Section: Discussionmentioning

confidence: 97%

“…Some studies have shown that the dull red luminescence observed in the dolomite is commonly associated with early formed dolomite during shallow burial environment (Jiang et al ., ; Zohdi et al ., ). The zoned CL images of RD3, RD4 and RD5 reflect variations of the chemical composition of diagenetic fluids reflecting various redox conditions, particularly Fe and Mn contents, during the course of precipitation (Olanipekun et al ., ; Zohdi et al ., ; Hou et al ., ).…”

Section: Discussionmentioning

confidence: 97%

“…This may indicate that they formed at low temperatures and at a relatively early stage of diagenesis (Sibley and Gregg, ; Gregg et al ., ). Also, the lack of evaporite layers reflects dolomitization by diagenetic fluids that were possibly modified seawater or a mixture of meteoric and marine waters (Olanipekun et al ., ; Hou et al ., ). Similarly, the facies (such as mudstone and wackestone) replaced by RD1 dolomite in the Qal'eh Dokhtar Formation are poor in organic matter and contain no pyrite, indicating that bacterial sulphate reduction had no role in the formation of RD1.…”

Section: Discussionmentioning

confidence: 97%

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Multistage dolomitization in the Qal'eh Dokhtar Formation (Middle‐Upper Jurassic), Central Iran: petrographic and geochemical evidence

et al. 2016

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The late Jurassic Qal'eh Dokhtar Formation lithologically comprises three parts, from bottom to top, a lower sandstone unit, middle shale unit and an upper carbonate unit, which extend in a N–S direction over a wide area to the east of the Shotori Range and west of the Lut Block (Central Iran). This succession was deposited on a mixed carbonate–siliciclastic ramp. Carbonate rocks of the Qal'eh Dokhtar Formation vary from undolomitized, to partly dolomitized, to completely dolomitized. Field observations from two measured sections (the type section, 955 m thick, and the Sorond section, 639 m thick), combined with detailed petrographic and geochemical analyses, revealed the diverse types of dolomite in this formation. Five types of replacement dolomite and one type of dolomite cement were distinguished. Replacement dolomites (RD) consist of: (1) fine crystalline planar‐s (RD1); (2) medium crystalline planar‐s (RD2); (3) medium crystalline planar‐e (RD3); (4) coarse crystalline planar‐s (RD4); and (5) coarse crystalline planar‐e (RD5). Coarse crystalline planar dolomite cements (DC) were observed in low abundance and filling dissolution voids and fractures. Variation in dolomite types is mainly related to early to late diagenetic processes leading to changes in composition of the dolomitizing fluids. Replacement dolomites are non‐stoichiometric (Ca43‐56–Mg34‐45) with Sr, Mn and Fe concentrations of 41–138 ppm, 168–919 ppm and 5000–21000 ppm, respectively. These dolomites are characterized by δ18O values ranging from 0.0 to –11.8 ‰ VPDB and δ13C values of +1.1 to +3.2 ‰ VPDB. These values are depleted in δ18O relative to the postulated values for late Jurassic dolomites precipitated in equilibrium with seawater, while δ13C values are within the range of Jurassic seawater dolomite values. Fluid inclusion data of RD4, RD5 and DC yield homogenization temperatures of 72 to 118 °C. Based on petrographic, fluid inclusion microthermometric data and geochemical results, the replacement dolomites in the Qal'eh Dokhtar Formation are interpreted to have formed in the subsurface at shallow to intermediate burial depths. These dolomites were then recrystallized at increased burial depths and temperatures. Seawater was the major source of Mg2+ for early diagenetic dolomite (DR1), while Mg2+ for late diagenetic dolomites was provided from diagenesis of clay minerals in shales and mechanical compaction of mudstone in the Qal'eh Dokhtar Formation. The dolomite cement is postdated by coarsely crystalline mosaic calcite cement indicating that diagenetic fluids eventually became undersaturated with respect to dolomite and oversaturated with respect to calcite. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 97%

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Multistage dolomitization in the Qal'eh Dokhtar Formation (Middle‐Upper Jurassic), Central Iran: petrographic and geochemical evidence

et al. 2016

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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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Variation of geochemical data and sedimentary characteristics in the Upper Cretaceous Ilam Formation, a case study from southwest Iran

Mehmandosti

Abdolmaleki

Hormoz³

et al. 2022

Palaeobio Palaeoenv

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Origin of the Breno and Esino dolomites in the western Southern Alps (Italy): Implications for a volcanic influence

Cited by 30 publications

References 77 publications

Multistage dolomitization in the Qal'eh Dokhtar Formation (Middle‐Upper Jurassic), Central Iran: petrographic and geochemical evidence

Multistage dolomitization in the Qal'eh Dokhtar Formation (Middle‐Upper Jurassic), Central Iran: petrographic and geochemical evidence

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

Variation of geochemical data and sedimentary characteristics in the Upper Cretaceous Ilam Formation, a case study from southwest Iran

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