Petrogenesis of alkaline basalt-hosted sapphire megacrysts. Petrological and geochemical investigations of in situ sapphire occurrences from the Siebengebirge Volcanic Field, Germany

Baldwin, Lisa; Tomaschek, Frank; Ballhaus, Chris; Gerdes, Axel; Fonseca, Raúl O. C.; Wirth, Richard; Geisler, Thorsten; Nagel, T.

doi:10.1007/s00410-017-1362-0

Cited by 28 publications

(32 citation statements)

References 99 publications

(122 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Research over the last decade has greatly improved our knowledge of the genesis of sapphire-bearing lamprophyres in Montana Palke et al, 2016Palke et al, , 2017 and gem corundum-bearing alkali basalts (Graham et al, 2008;Uher et al, 2012;Baldwin et al, 2017;. The sapphires and/or rubies are xenocrysts and more rarely megacrysts in xenoliths formed under metamorphic and/or magmatic conditions (figures 4B, D).…”

mentioning

confidence: 99%

“…Studies of the BGY sapphires and ruby in alkali basalts (figure 4) focused on solid inclusions Baldwin et al, 2017;Palke et al, 2018), trace element geochemistry (Peucat et al, 2007), oxygen isotopes (Yui et al, 2003;Giuliani et al, 2005) (Rakotozamizanany et al, 2014) to show that the gem corundum may have different magmatic and metamorphic origins. Within a single gem province in Australia, variations in color observed for corundum found ~10 km apart suggest the existence of multiple sources for the gemstones (Sutherland et al, 1998a;Sutherland and Schwarz, 2001).…”

mentioning

confidence: 99%

“…Several hypotheses have been advanced to explain the formation of magmatic sapphires: crystallization from highly evolved melts, most likely syenites (Uher et al, 2012); partial melting of amphibole-bearing lithosphere (Sutherland et al, 1998b); reaction of a fractionated silicate melt with a carbonatitic melt (Guo et al, 1996); partial melting of Al-rich rocks of the crust (such as anorthosites; Palke et al, 2016Palke et al, , 2017; and a carbonatitic melt exsolved from highly evolved phonolites (Baldwin et al, 2017).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Geology of Corundum and Emerald Gem Deposits: A Review

Giuliani¹,

Groat²

2019

G&G

View full text Add to dashboard Cite

The great challenge of geographic origin determination is to connect the properties and features of individual gems to the geology of their deposits. Similar geologic environments can produce gems with similar gemological properties, making it difficult to find unique identifiers. Over the last two decades, our knowledge of corundum and emerald deposit formation has improved significantly.The mineral deposits are classically separated into primary and secondary deposits. Primary corundum deposits are subdivided into two types based on their geological environment of formation: (1) magmatic and (2) metamorphic. Magmatic deposits include gem corundum in alkali basalts as in eastern Australia, and sapphire in lamprophyre and syenite as in Montana (United States) and Garba Tula (Kenya), respectively. Metamorphic deposits are divided into two subtypes (1) metamorphic deposits sensu stricto (in marble; mafic and ultramafic rocks, or M-UMR), and (2) metamorphicmetasomatic deposits characterized by high fluid-rock interaction and metasomatism (i.e., plumasite or desilicated pegmatites in M-UMR and marble, skarn deposits, and shear zone-related deposits in different substrata, mainly corundum-bearing Mg-Cr-biotite schist). Examples of the first subtype include the ruby deposits in marble from the Mogok Stone Tract or those in M-UMR from Montepuez (Mozambique) and Aappaluttoq (Greenland). The second subtype concerns the sapphire from Kashmir hosted by plumasites in M-UMR.Secondary corundum deposits (i.e., present-day placers) result from the erosion of primary corundum deposits. Here, corundum is found in the following types of deposits: eluvial (derived by in situ weathering or weathering plus gravitational movement), diluvial (scree or talus), colluvial (deposited at the base of slopes by rainwash, sheetwash, slow continuous downslope creep, or a combination of these processes), and alluvial (deposited by rivers). Today, most sapphires are produced from gem placers related to alkali basalts, as in eastern Australia or southern Vietnam, while placers in metamorphic environments, such as in Sri Lanka (Ratnapura, Elahera) and Madagascar (Ilakaka), produce the highest-quality sapphires. The colluvial Montepuez deposit in Mozam bique provides a huge and stable supply of clean and very highquality rubies. Primary emerald deposits are subdivided into two types based on their geological environment of formation: (1) tectonic-magmatic-related (Type I) and (2)tectonic-metamorphic-related (Type II). Several subtypes are defined and especially Type IA, hosted in M-UMR, which accounts for about 70% of worldwide production (Brazil, Zambia, Russia, and others). It is characterized by the intrusion of pegmatites or quartz veins in M-UMR accompanied by huge hydrothermal fluid circulation and metasomatism with the formation of emerald-bearing desilicated pegmatite (plumasite) and biotite schist. Type IB in sedimentary rocks (China, Canada, Norway, Kazakhstan, and Australia) and Type IC in granitic rocks (Nigeria) are of minor importance.T...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Geology of Corundum and Emerald Gem Deposits: A Review

Giuliani¹,

Groat²

2019

G&G

View full text Add to dashboard Cite

show abstract

“…These findings were in accordance to those of Le Bas [52], who interpreted the presence of abundant primary carbonate and olivine inclusions in the zircon megacrysts to be indicative of the growth in a silica-undersaturated, carbonatite-like melt. The experimental work of Baldwin [53] demonstrates that corundum and olivine likely crystallize from carbonatitic melts during early phases. However, no carbonatite bodies were reported from the studied area in the Central Highlands, Vietnam.…”

Section: Discussionmentioning

confidence: 99%

Gem-Quality Zircon Megacrysts from Placer Deposits in the Central Highlands, Vietnam—Potential Source and Links to Cenozoic Alkali Basalts

et al. 2019

View full text Add to dashboard Cite

Gem-quality zircon megacrysts occur in placer deposits in the Central Highlands, Vietnam, and have euhedral to anhedral crystal shapes with dimensions of ~3 cm in length. These zircons have primary inclusions of calcite, olivine, and corundum. Secondary quartz, baddeleyite, hematite, and CO2 fluid inclusions were found in close proximity to cracks and tubular channels. LA-ICP-MS U-Pb ages of analyzed zircon samples yielded two age populations of ca. 1.0 Ma and ca. 6.5 Ma, that were consistent with the ages of alkali basalt eruptions in the Central Highlands at Buon Ma Thuot (5.80–1.67 Ma), Pleiku (4.30–0.80 Ma), and Xuan Loc (0.83–0.44 Ma). The zircon geochemical signatures and primary inclusions suggested a genesis from carbonatite-dominant melts as a result of partial melting of a metasomatized lithospheric mantle source, but not from the host alkali basalt. Chondrite-normalized rare earth element patterns showed a pronounced positive Ce, but negligible Eu anomalies. Detailed hyperspectral Dy3+ photoluminescence images of zircon megacrysts revealed resorption and re-growth processes.

show abstract

“…Collectively, there is a range in δ 18 O from 4.1% to 11.2% and a range in Ga/Mg of 0.3-10.4 (average range of 0.73-7.7) but no correlation or apparent relationship between Ga/Mg and the oxygen isotope values. Importantly, Baldwin et al (2017) [19] found that sapphire megacrysts from the Siebenbirge Volcanic Field of Germany had a wide Ga/Mg of 1.0-23.4 and ascribed this to the influence of a carbonatitic melt in the crystallization of the sapphires. The range in Ga/Mg values for Jujuy Province sapphires at 0.30-10.40 fits well within this range and, based on this alone, would tentatively suggest a similar mechanism of formation.…”

Section: Oxygen Isotope Groupingsmentioning

confidence: 99%

Enigmatic Alluvial Sapphires from the Orosmayo Region, Jujuy Province, Northwest Argentina: Insights into Their Origin from in situ Oxygen Isotopes

Graham¹,

Harris²,

Martin³

et al. 2019

Minerals

View full text Add to dashboard Cite

This study sought to investigate in situ oxygen isotopes (δ18O) within alluvial colorless-white to blue sapphires from the Orosmayo region, Jujuy Province, NW Argentina, in order to provide additional constraints on their origin and most likely primary geological environment. Analyses were conducted using the in situ SIMS oxygen isotope technique on the same grains that were analyzed for their mineral inclusions and major and trace element geochemistry using EMPA and LA–ICP–MS methods in our previous study. Results show a significant range in δ18O across the suite, from +4.1‰ to +11.2‰. Additionally, akin to their trace element chemistry, there is significant variation in δ18O within individual grains, reaching a maximum of 1.6‰. Both the previous analyses and δ18O results from this study suggest that these sapphires crystallized within the lower crust regime, involving a complex interplay of mantle-derived lamprophyres and carbonatites with crustal felsic rocks and both mantle- and crustal-derived metasomatic fluids. This study reinforces the importance of the in situ analysis of gem corundums, due to potential significant variation in major and trace element chemistry and ratios and even oxygen isotope ratios within discrete zones in individual grains.

show abstract

Petrogenesis of alkaline basalt-hosted sapphire megacrysts. Petrological and geochemical investigations of in situ sapphire occurrences from the Siebengebirge Volcanic Field, Germany

Cited by 28 publications

References 99 publications

Geology of Corundum and Emerald Gem Deposits: A Review

Geology of Corundum and Emerald Gem Deposits: A Review

Gem-Quality Zircon Megacrysts from Placer Deposits in the Central Highlands, Vietnam—Potential Source and Links to Cenozoic Alkali Basalts

Enigmatic Alluvial Sapphires from the Orosmayo Region, Jujuy Province, Northwest Argentina: Insights into Their Origin from in situ Oxygen Isotopes

Contact Info

Product

Resources

About