Major and Trace Element Geochemistry of Dayakou Vanadium-Dominant Emerald from Malipo (Yunnan, China): Genetic Model and Geographic Origin Determination

Abstract

Emerald from the deposit at Dayakou is classified as a vanadium-dominant emerald together with Lened, Muzo, Mohmand, and Eidsvoll emeralds. Although previous studies defined these V-dominant emeralds and traced the genesis of the Dayakou deposit, there has not been any systematic comparison or discrimination on V-dominant emeralds from these deposits. The origin of the parental fluid and the crystallization process of the Dayakou emerald remain controversial. In this study, both major and trace element signatures of 34 V-dominant samples from Dayakou are analyzed through electron microprobe analysis (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Dayakou emeralds are characterized by high ratios of V/Cr and the enrichment of Li, Cs, W, Sn, and As. These geochemical fingerprints indicate a parental fluid of an Early Cretaceous early-stage granitic fluid associated with Laojunshan granite. The considerable concentration variation of Rb, Cs, Ga and the presence of V-rich oxy-schorl-dravite inclusions in a color zoned sample suggest two generations of emerald precipitation. Thus, a more detailed idealized mineralization model for the Dayakou deposit is proposed. A series of plots, such as Rb vs. Cs, V vs. V/Cr, LILE vs. CTE, and Li vs. Sc, are constructed to discriminate the provenance of V-dominant emeralds. Minerals 2019, 9, 777 2 of 29 summarized emerald deposits worldwide and collected their chemical compositions. They defined Dayakou (China), Lened (Canada), Muzo (Colombia), Mohmand (Pakistan), and Eidsvoll (Norway) emeralds as typical V-dominant emeralds based on the greater content of V 2 O 3 than Cr 2 O 3 . Those V-dominant emeralds can be easily distinguished from Cr-dominant emeralds. However, there has not been a systematic comparison or discrimination of those V-dominant emeralds from various deposits. With regards to Dayakou emeralds, their chemical compositions have been recently reported [20], but not analyzed in detail. Trace elements of emerald are powerful indicators for determining the geographic provenance but the number of related studies is limited. For the first time, using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS) techniques, [21] and [16] determined the origin of emeralds from several deposits by trace elements data, such as Li, B, Rb, Cs, V, Cr, Sc, Ga, etc. So far, only [20] has reported trace elements of Dayakou emerald, but their work focused on the Al 3+ replacement degree and Cr/V ratio. The geochemical fingerprints of the Dayakou emerald are not yet determined.Besides, the trace element geochemistry of emeralds was used for building the genetic model. B, Ga, Ba, Sr, and alkali elements Li, Cs, and Rb are regarded as indicators of parental fluid and the fractionation and evolution for pegmatite [3,4,22,23]. Reference [24] reported the formation conditions of Dayakou emerald, but the crystallization process and the sources of emerald-forming fluids have yet to be determined.In thi...

Spectroscopy and Trace-Element Characteristics of Emeralds from Kamakanga, Zambia

“…According to the attribution of absorption peaks, the absorption peaks in the range of 3800 to 1400 cm −1 of the emerald infrared spectrum can be divided into three parts: the absorption peaks at 3800-3500 cm −1 are caused by channel water stretching vibration (Figure 4a); the absorption peaks at 3000-2000 cm −1 are caused by CO2 or cedarwood oil (Figure 4b); the absorption peaks at 1700-1500 cm −1 are caused by channel water bending vibration (Figure 4c) [23,24]. As shown in Figure 4, the peaks at 3590 cm −1 of type I H2O were sharp and strong, while the peaks at 3564 or 3566 cm −1 of type II H2O were sharp but weak.…”

Overview of Gemstone Resources in China

“…The Dayakou emeralds are green, bluegreen, yellow-green, and color zonations common, showing a light green and white core and a green rim. The crystal clarity is poor, with numerous healing cracks and fractures penetrating the surface and clusters of fluid inclusions [55,56]. The crystal is usually hexagonal columnar or plate-shaped, with obvious longitudinal lines, irregular erosion marks, and hexagonal pits on the cylindrical surface, and the particle size is generally 0.5~5 cm (Figure 3f).…”

“…The crystal is usually hexagonal columnar or plate-shaped, with obvious longitudinal lines, irregular erosion marks, and hexagonal pits on the cylindrical surface, and the particle size is generally 0.5~5 cm (Figure 3f). The major composition of Dayakou emerald is characterized by a higher concentration of V than Cr, defined as the V-dominant emerald [56]. The Al 3+ at the Y position of the octahedron in the lattice is unsaturated, mainly replaced by Mg 2+ , V 3+ , Fe 2+ ; the channel of the beryl crystal is dominated by Na.…”

Inclusion and Trace Element Characteristics of Emeralds from Swat Valley, Pakistan

“…Several published studies represent an early attempt to use trace elements for provenance purposes (Saeseaw et al, 2014(Saeseaw et al, , 2019Carlo et al, 2018), but the data for Swat emeralds is scarce. In this study, 27 spots on 11 regular Swat emeralds were analyzed via LA-ICP-MS. Logarithm plots of trace elements were applied to detect possible correlations when distinguishing geographic origin, so adding LA-ICP-MS data from other main emerald deposits in the world is necessary, such as Colombia, Kafubu from Zambia, Brazil (Zwaan et al, 2012), Panjshir from Afghanistan, Swat from Pakistan (Carlo et al, 2018), Khaltaro from Pakistan (Laurs et al, 1996), Russia (Saeseaw et al, 2019;Carlo et al, 2018;Karampelas et al, 2019;all averages), Ethiopia (Saeseaw et al, 2019;Carlo et al, 2018;Karampelas et al, 2019;all averages), Egypt (Carlo et al, 2018), India (Carlo et al, 2018, and Malipo from China (Zheng et al, 2019). The inclusions of Ethiopian and Russian emeralds (Saeseaw et al, 2019) Laurs et al (1996), Zwaan et al (2012), andZheng et al (2019).…”