Constraints on Crystallinity of Graphite Inclusions in Nephrite Jade from Xinjiang, Northwest China: Implications for Nephrite Jade Formation Temperatures
by
, and
Jifei Zheng
1,2,
Lei Chen
3,
Cun Zhang
4,
Yue Liu
4,
Ruicong Tian
5,
Jinlin Wu
6,
Yu Wu
7 and
Shouting Zhang
1,2,* 1
School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China
2
Frontiers Science Center for Deep-Time Digital Earth, China University of Geosciences (Beijing), Beijing 100083, China
3
Shandong Geological Survey Institute, 17 Jingshan Road, Jinan 250020, China
4
School of Materials Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), 3501 Daxue Road, Jinan 250353, China
5
School of Geography and Tourism, Qilu Normal University, Jinan 250020, China
6
National Gemstone Testing Center Shenzhen Laboratory Company Ltd., Shenzhen 518020, China
7
Gemological Inspection Institute of Xinjiang Zhongjian, Xinjiang 830002, China
*
Author to whom correspondence should be addressed.
Minerals 2023, 13(11), 1403; https://doi.org/10.3390/min13111403
Submission received: 21 September 2023
/
Revised: 16 October 2023
/
Accepted: 24 October 2023
/
Published: 1 November 2023
(This article belongs to the Special Issue Graphite Minerals and Graphene)
Abstract
:Graphite usually occurs in mineral/rock associations in the form of solid inclusions and plays an important role in tracing regional metamorphic degree, ore-forming temperature, fluid evolution, as well as the deep carbon cycle of the Earth. In this study, we investigate the placer black nephrite jade where the co-occurrence of abundant graphite inclusions and jade remains extraordinary. By employing petrographic, mineral-chemical, and Raman spectroscopic methods, we characterize the textures and crystallinity of graphite inclusions that exist in nephrite jade. EPMA and petrological data indicate that the main constituents of black jade are tremolite and graphite, with minor phases of diopside, calcite, dolomite, epidote, and apatite. Micro-Raman spectroscopic thermometry of carbonaceous material shows that most of the formation temperatures of graphite inclusions are between 378 and 556 °C, and only a few temperatures may be above 650 °C, indicating that graphite inclusions were formed at medium- to high-temperature metamorphic facies. The petrologic and spectral investigations of graphite inclusions in these nephrite jade samples show major metamorphic signatures with mixed features associated with fluid precipitation. Our results allow us to propose that primary nephrite jade was formed under multi-stage tectonic evolution conditions, and regional temperatures were predominately driven by the late continent–continent collision, while the ore-controlling temperatures of nephrite jade formation were found in a medium- to high-temperature environment.
1. Introduction
Nephrite jade with high economic values consists mainly of fibrous amphibole, which includes mostly tremolite and actinolite to ferro-actinolite together with minor accessory or secondary minerals [1,2,3]. Previous investigations have been carried out on world-class nephrite jade deposits to determine their genesis through gemological properties, geochronology, mineral chemistry, major and trace elements, as well as H-O and Sr isotopic compositions [4,5,6,7,8]. Recently, Zhang et al. [2] summarized the spatial and temporal distribution, metallogenic mechanisms, and genetic types of nephrite deposits in China, and provided insights for genetic discrimination, future exploration of the reserves, occurrence states of nephrite jade deposits, as well as tectonic models for nephrite jade formation. However, only a few studies have focused on mineral inclusions in nephrite jade, especially graphite inclusions, which exert important implications for evaluating geological evolution processes and non-metallic metallogenic tectonic settings [4,8]. Zhang et al. [9] indicated that the graphite inclusions in green nephrite jade from Liaoning Province, China, were formed either in high- or low-temperature metamorphic facies, suggesting the difference in the formation stages of nephrite jade. Moreover, Yui et al. [4] obtained temperature information of 410–430 °C for the Hualien green nephrite jade in Taiwan Province, China, indicating that the jade should have formed in a low P/T environment. These studies were limited to the crystallization characteristics and formation temperatures of graphite inclusions in green nephrite jade generated from the eastern nephrite jade belt along the Pacific Ocean based on Raman micro-thermometry [4,9]. In contrast, the graphite inclusions are especially enriched in white jade-type (WJ-type) nephrite jade, especially in placer black nephrite jade with high economic value from Xinjiang Province [4]. According to previous research, the two types of black nephrite jade can be defined as (1) jade with tremolite and actinolite as the main components; and (2) jade with tremolite and graphite as the main minerals [2,5,6]. Although the types and origin of black nephrite jade have been studied in detail, the formation temperatures, regional metamorphic degree, and the relationship between graphite inclusions and jade formation have not yet been fully investigated, and further research is needed.
The transformation of carbonaceous materials (CM) to graphite during metamorphism, a process termed as graphitization, is a function of the degree of metamorphism and can be quantitatively constrained by Raman spectroscopy [10,11,12]. This process provides robust information for studying graphitic carbon, which offers the significant advantages of rapid, minimal, non-destructive sample preparation and in situ analysis, thus preserving the original textural information. The approximate disorder mode (D1), disorder of edge carbon (D2), and ordered mode (G) structures, as well as quantitative parameters D1/G intensity ratio (R1), D1/(D1 + G) area ratio (R2), and the G band full width at half maximum (FWHM) of the Raman spectra of graphite can be used as indicators of the metamorphic grade and processes, as well as for determining the thermal alteration (maturity) of organic matter (OM) and aiding in the identification of fluid-precipitated graphite [9,13,14,15,16]. However, no detailed studies have been conducted so far to characterize the occurrence and genesis of these graphite inclusions by Raman spectroscopy in placer or secondary black nephrite jade.
The objective of this study is to characterize abundant graphite inclusions generated in placer black nephrite jade from Xinjiang, Northwest China, based on petrology, EPMA, and Raman spectroscopy, with a view to trace the nature of the graphite and the formation temperatures of graphite and nephrite jade. This paper presents interesting research samples and new thoughts on carbon sequestration and deep carbon cycling. Our approach also provides an indicative window in relation to graphite crystallization associated with the formation of nephrite jade at different stages of metamorphism.
2. Materials and Methods
2.1. Geological Background of Xinjiang Nephrite Jade Belt
The WJ-type nephrite jade deposits are mainly generated in the Nephrite Jade Belt of the West Kunlun and Altun Mountains in the southern Xinjiang province, China (Figure 1). The spatial distribution of these deposits in this area present NW–EW–NE linear structures, extending from Tashinkurgan to Ruoqiang County. A large number of primary deposits hosted in the 1300 km range of mountains were excavated, which can be subdivided into Shache-Yecheng, Hetian-Yutian, and Qiemo-Ruoqiang, respectively [2,5,6,17,18] (Figure 1b). Moreover, the Yurungkash River (White Jade River) and the Kharakash River (Black Jade River) are rich in high-quality placer or secondary nephrite jade (Figure 1b). Particularly, the black nephrite jade with abundant graphite inclusions is produced from the latter. Previous investigations suggest that their primary ore bodies generally occur in the contact zones of dolomitic marbles and intermediate-felsic rocks or mafic rocks, while the placer nephrite jade is transported by glacial meltwater and then deposited into a river (or bed) from the primary deposits in the Kunlun Mountains [2,5,6] (Figure 1b). Notably, the black nephrite jade with graphite inclusions could play an important role in revealing the complex cycle of graphite formation and tectonic evolutionary history of primary ore deposits.
2.2. Materials
Graphite-bearing nephrite jade samples (labeled as QHL) for this study were collected from Kharakash River (Black Jade River). The nephrite jade samples with a waxy-grease luster show fine textures and block structures, and the color is mostly gray-black to black, with some samples containing opaque white flocculi inside (Figure 2). In appearance, the color of nephrite jade is attributed to graphite inclusions instead of chemical elements, thus being defined as black nephrite jade. The graphite inclusions are mostly distributed in the white cryptocrystalline tremolite particles in the form of bands, and well-crystallized graphite crystals show flaky characteristics with semi-metallic luster. The whole placer materials present spheroidal or nearly elliptic features, with a small number of pores and cracks being observed on the surface (Figure 2). This is because nephrite jade has experienced fluvial abrasion and collision during the process of transportation from the primary ore to the river (or bed).
2.3. Methods
The electron microprobe analyses (EPMA) and backscattered electron (BSE) and surface scanning of the samples were performed at the Shandong Institute of Geological Sciences (SIGS) using a JEOL JXA-8230 microprobe with an accelerating voltage of 15 kV, a beam current of 2 × 10−8 A, and a beam spot diameter of 0.5 μm. The data collection time was 20–60 s. The ZAF method was used to correct the data, and the analysis accuracy was less than 1%. The chemical compositions of different samples were analyzed using Wavelength Dispersive Spectroscopy (WDS). The standard samples used were Canadian Astimex company series standard samples, and the detection standards were as follows: potassium feldspar (K), jadeite (Na), corundum (Al), quartz (Si), forsterite (Mg) and rutile (Ti), hematite (Fe), calcite (Ca), fluorite (F) and rock salt (Cl), apatite (P), huebnerite (Mn), chromic oxide (Cr), and nickelic (Ni) oxide.
Raman spectroscopy of graphite was performed at the National Gemstone Testing Center Shenzhen Lab., using a Renishaw instrument on glass plates. The wavelength used was 532 nm, and the instrument setup allowed a spectral resolution of 1 cm−1. We used a scanning time of 10 s of spectrum in an extending mode spanning 100~4000 cm−1 with a grating of 1800 I/mm and a 50× lens. Filters allowed us to set the laser power on the sample at around 1 mW to avoid degradation of the carbonaceous material (CM). Before each session, the spectrometer was calibrated with a silicon standard. Because the Raman analysis of graphite can be affected by several analytical mismatches, we closely followed the analytical protocol established by Beyssac et al. [10,11].
3. Results and Discussion
3.1. Petrology
Petrographic studies using a polarizing microscope show that the QHL samples occur predominantly in distinct textural associations. The main textures of nephrite jade are felt-like aphanoblastic and microfibrous, indicating its high-quality properties. The main mineral compositions of nephrite jade are tremolite, and the accessory or secondary minerals are diopside, calcite, apatite, epidote, and graphite (Figure 3a–f). Most of the graphite disseminations occur in association with the main minerals. Under reflected light, the graphite inclusions show a light yellow-brownish color (Figure 3d), and occur as platy or spotted crystals. They most commonly occur as flakes and lamellae, and some of the graphite crystals show “flow” textures, possibly from being filled along cracks or veins (Figure 3d). Generally, the graphite grains are distributed randomly among tremolite grains, suggesting the absence of obvious contacting reaction boundaries.
3.2. Mineral Chemistry
The mineral EPMA analysis results are presented in Figure 4 and Table 1, Table 2 and Table 3. The EPMA data suggest the mineral assemblages are tremolite, diopside, calcite, dolomite, and apatite, which is consistent with the assemblages observed in the petrographic study (Table 1 and Table 2). The predominant chemical components of the tremolite are SiO2, MgO, and CaO, in the ranges of 56.47–59.03 wt.%, 23.85–24.62 wt.% and 12.25–13.43 wt.%, with the average values of 58.34 wt.%, 24.28 wt.%, and 12.74 wt.%, respectively. The contents of FeO are low, ranging from 0.16–0.63 wt.% with average value of 0.36 wt.%, suggesting that it could not cause the samples to appear black colors. Calcic amphiboles are characteristically Mg-rich, with Mg2+/(Mg2+ + Fe2+) ranging between 0.99 and 1.00, which further indicates that the main mineral of black nephrite jade is tremolite (Figure 1; Table 1). The chemical compositions of apatite show that the contents of P2O5 range from 41.93 to 43.86 wt.%, with an average value of 42.75 wt.%. The contents of CaO range from 54.95 to 55.87 wt.%, with an average value of 55.42 wt.%. The contents of F range from 2.32 to 3.10 wt.%, with an average value of 2.67 wt.%, while the contents of Cl range from 0.06 to 0.23 wt.%, with an average value of 0.14 wt.% (Table 3). Generally, the contents of F are much higher than that of Cl, which indicates typical fluorapatite characteristics, suggesting indicating that the formation and evolution of primary nephrite jade was accompanied by complex F volatilization cycle.
3.3. Raman Spectroscopy: Structural Features of Graphite Inclusions
The results of the Raman spectroscopic analyses of graphite inclusions are displayed in Figure 5, Figure 6, Figure 7, Figure 8 and Figure 9, and the data are given in Table 4. Raman spectroscopy shows that peaks of 225 cm−1 are attributed to the lattice vibration of tremolite, but the 395 cm−1 is between cation to oxygen vib. (M-O) (e.g., Ca, Mg-O). The peak at 550 cm−1 represents the bending vibration of Si-O. The peaks at 673-679 cm−1 are due to the Si-O-Si stretching vibration and can be attributed to substituting Mg2+ with the heavier Fe2+ [20]. The peaks at 928–932 cm−1 are due to the stretching O-Si-O vibration, and peaks at 1025 to 1060 cm−1 are the antisymmetric Si-O-Si of tremolite. The peaks at 3669–3670 cm−1 belong to the OH stretching vibration [20]. The small difference in wave numbers indicates it may be related to the interionic substitution and occupation. The above spectral peaks indicate that the main mineral of black nephrite jade is tremolite, which is consistent with the results of petrographic studies.
Raman spectroscopy of graphite inclusions in black nephrite jade is mainly divided into two order regions: the first-order region (1100–1800 cm−1) and the second-order region (2300–3400 cm−1), respectively (Figure 5, Figure 6, Figure 7, Figure 8 and Figure 9). The first-order region mainly includes three main peaks: D1, G, and D2 peaks [21]. No disordered “graphitic carbon” peaks were detected at D3 and D4 in any of the nephrite jade samples [22]. The second-order region predominately consists of five peaks, namely S1, S2, S3, and S4. The G and S2 peak positions were determined at maximum intensity, and the results show that the sharp G peak is in the range of 1576–1580 cm−1, while the stable peak S2 varies from 2710 to 2716 cm−1. The band full width at half maximum of the G band of graphite varies from 16.31 to 59.56 (Table 4). These values indicate similar the structural features and good crystallinity of graphite, suggesting that it formed under medium- to high-temperature conditions [14]. Previous investigation suggested that metamorphic graphite in the forms of disordered to ordered flakes shows variable crystallinity, while the fluid-deposited graphite exhibits high crystallinity and homogeneity at high-temperature settings [23]. In this study, the petrographic features of most graphite types show affinity to regional metamorphic graphite [24]. The variation and differentiation in the spectroscopic characteristics of graphite inclusions in black nephrite jade reveal that the jade experienced gradual and progressive regional metamorphism during its formation processes. However, the obvious asymmetrical peak at 2710–2714 cm−1 of the S band in the sample QHL-4 indicates typically well-crystallized graphite, which has reached perfect three-dimensional ordering, revealing hydrothermal graphitic C [25,26,27]. These features are similar to graphite precipitated from carbonic fluid infiltration during higher-temperature metamorphism.
3.4. Formation Temperatures of Graphite Inclusions
The first order region of Raman spectrum of graphite was decomposed by Lorentz function peak fitting method using software Origin 9.0, and the results are presented in Table 4. However, the graphite Raman geothermometers used do not work for the carbon spectrum without the D band, indicating that the formation temperature was above the upper limit. In this study, the metamorphic temperatures of graphite inclusions of black nephrite jade are estimated using the quantitative parameter of area ratio (R2), which is defined as D1/(G + D1 + D2) (R2), while the D2 peak area is generally negligible [10,11,23,28,29]. The decomposition peak in the first order region of graphite Raman spectrum show that the R2 varies by 0.28–0.59 with an average value of about 0.41, except for partial QHL-4 samples that exceeded its working limit. The graphite inclusions formation temperatures were calculated by Equations (1) and (2), based on Beyssac et al. [10,11] and Aoya et al. [29], respectively.
T(°C) = −445 × R2 + 641 (330 < T < 650), R2 = 0.96 ± 50 °C
T(°C) = 91.4 × (R2) 2 − 556.3 × R2 + 676.3 ± 30 °C
Most metamorphic temperatures ranged from 378 to 556 °C as calculated by the above equations, indicating that the graphite inclusions that existed in nephrite jade were formed in a moderate- to high-temperature environment. (Table 4). Previous investigations speculated that the P/T conditions for the formation of the primary nephrite jade deposit in Xinjiang were medium to low pressure (100–200 MPa) and at temperatures of 330–550 °C based on nephrite zonal structure and minor minerals [5,6,23]. The results of our present study are consistent with the previous conjecture, which further confirms the reliability of the temperature constraint. The sample QHL-4 shows a high degree of crystallization with similar properties to fluid-precipitated graphite, which may represent peak metamorphism.
Table 4.
Quantitative parameters of Raman spectroscopy and formation temperatures of different graphite inclusions in placer black nephrite jade samples.
Table 4.
Quantitative parameters of Raman spectroscopy and formation temperatures of different graphite inclusions in placer black nephrite jade samples.
| Sample | Peak D1I1 | Peak GI2 | D1/G Intensity R1 Ratio | Peak D1A1 | Peak GA2 | D1/(G + D1 + D2) R2 Area Ratio | Position of the G | Position of the S2 | G FWHM | Equation (1)/T (°C) | Equation (2)/T (°C) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| QHL-1/1-1 | 10,451 | 17,881 | 0.58 | 530,407 | 416,809 | 0.56 | 1580 | 2711 | 23.39 | 391.82 | 393.45 |
| QHL-1/1-2 | 10,408 | 17,809 | 0.58 | 530,813 | 417,109 | 0.56 | 1579 | 2711 | 23.43 | 391.81 | 393.45 |
| QHL-1/1-3 | 23,643 | 59,248 | 0.40 | 1,241,670 | 1,265,554 | 0.50 | 1577 | 2711 | 18.57 | 420.62 | 423.22 |
| QHL-1/1-4 | 15,269 | 39,202 | 0.39 | 236,027 | 813,779 | 0.22 | 1578 | 2714 | 16.84 | 540.95 | 555.85 |
| QHL-2/1-1 | 13,930 | 48,465 | 0.29 | 910,337 | 2,213,573 | 0.29 | 1580 | 2717 | 13.90 | 511.32 | 521.95 |
| QHL-2/1-2 | 12,153 | 22,997 | 0.53 | 681,820 | 785,513 | 0.46 | 1580 | 2711 | 29.03 | 434.22 | 437.54 |
| QHL-2/2-1 | 18,099 | 53,542 | 0.34 | 1,061,735 | 2,768,686 | 0.28 | 1579 | 2711 | 18.76 | 517.65 | 529.12 |
| QHL-2/2-2 | 18,388.2 | 42,488 | 0.43 | 658,790 | 1,026,631 | 0.39 | 1579 | 2712 | 17.12 | 467.06 | 472.82 |
| QHL-2/3-1 | 21,422 | 75,648 | 0.28 | 727,249 | 1,826,157 | 0.28 | 1579 | 2716 | 16.31 | 514.26 | 525.27 |
| QHL-3/1-1 | 30,507 | 50,849 | 0.60 | 1,665,856 | 1,138,157 | 0.59 | 1579 | 2715 | 20.83 | 376.63 | 378.06 |
| QHL-3/1-2 | 26,394 | 44,506 | 0.59 | 1,057,764 | 2,848,420 | 0.28 | 1579 | 2711 | 19.90 | 520.50 | 532.36 |
| QHL-3/1-3 | 21,925 | 30,496 | 0.72 | 1,135,422 | 928,298 | 0.55 | 1579 | 2713 | 26.97 | 396.17 | 397.90 |
| QHL-4/1-1 | 14,453 | 63,097 | 0.23 | 1,274,335 | 3,005,349 | 0.30 | 1579 | 2711 | 14.94 | 508.50 | 518.76 |
| QHL-4/1-2 | 0 | 41,639 | 0.00 | n. d. | n. d. | n. d. | 1577 | 2714 | n. d. | 641.00 | 676.30 |
| QHL-4/1-3 | 0 | 39,422 | 0.00 | n. d. | 295,479 | n. d. | 1577 | 2711 | 16.33 | 641.00 | 676.30 |
| QHL-4/1-4 | 0 | 38,924 | 0.00 | n. d. | 254,790 | n. d. | 1579 | 2712 | 18.13 | 641.00 | 676.30 |
| QHL-4/1-5 | 0 | 44,316 | 0.00 | n. d. | n. d. | n. d. | 1577 | 2714 | n. d. | 641.00 | 676.30 |
| QHL-5/1-1 | 47,844 | 83,589 | 0.64 | 4,161,000 | 4,449,380 | 0.49 | 1576 | 2711 | 59.56 | 425.95 | 428.81 |
T (°C) = −445 × R2 + 641, R2 = 0.96 (1); T (°C) = 91.4 × (R2) 2 − 556.3 × R2 + 676.3 (2) [10,11,29]. Note: D1I1: intensity of D1, GI2: intensity of G, D1A1: peak area of D1, GA1: peak area of G, Full width at half maximum (FWHM), R2 area ratio of graphite spectrums were obtained using the Peakfit software Origin 9.0. n. d. = not discernible S. E. = Standard Error. In sample QHL-4/1-2 to QHL-4/1-5, the graphite Raman geothermometers used do not work for the carbon spectrum without the D band.
3.5. Implication for Graphite Growth and Nephrite Jade Formation
Graphite usually generated in meta-sediments, meta-carbonates, and skarn rocks can be attributed to distinct processes, and its carbon sources and the structural characteristics of Raman spectroscopy show different properties [27,30,31]. Generally, the WJ-type nephrite jade from Xinjiang was formed through the skarn-type metasomatism of intermediate-felsic granitic rocks and Precambrian dolomite marble [2,5,6,8]. Our recent work proposes that the formation mechanism model of WJ-type nephrite jade was formed through metamorphism/metasomatism during continent–continent collision [29]. The original carbon-bearing material may have been deposited in the carbonate rocks and subsequently subducted. The low crystallinity of graphite may also be due to the rapid deposition kinetics, possibly playing an underestimated role in the structural transformation of carbon. The micro and cryptocrystalline texture of the jade reflects conditions of high supersaturation of amphibole crystallization, probably caused by the rapid infiltration of SiO2-rich fluid with a non-equilibrium composition. Defective carbon can also precipitate from the fluid at high supersaturation [32]. In our present investigation, it can be assumed the crystalline graphite inclusions were finally formed at medium- to high-temperature metamorphic facies driven by late continental collisions, revealing the temperature changes experienced by the main minerals during the formation processes. Moreover, previous studies have confirmed that the graphite structures tend to record the peak metamorphic temperatures and do not recrystallize under retrograde conditions except in some extreme cases where they will be destroyed [12,23]. The metamorphic temperatures of 378~556 °C obtained from graphite Raman micro-thermometry provide a new perspective depicting the formation temperatures of nephrite jade.
4. Conclusions
Abundant graphite inclusions are enriched in the placer black nephrite jade in Xinjiang Province, Northwest China, which mostly show the characteristics of bands and flakes. This type of nephrite jade is colored by graphite inclusions instead of chemical elements. The Raman spectroscopic analyses show that the graphite inclusions generally present a good degree of crystallization, and the mineralization temperature of most of the graphite inclusions is under ~380–560 °C, indicating the regional metamorphic temperature in different stages or facies. Only a few crystalline graphite inclusions show fluid-related characteristics, and their carbon sources may be derived from magmatic intrusion during orogeny. The association of graphite inclusions and nephrite jade indicates that the metamorphic grade of primary nephrite deposits is situated in the facies of medium- and high-temperature transformation.
Author Contributions
Conceptualization, J.Z., C.Z. and S.Z.; methodology, C.Z., Y.L. and J.W.; writing—original draft preparation, J.Z., L.C., C.Z., Y.L., R.T., J.W., Y.W. and S.Z.; writing—review and editing, J.Z. and C.Z.; supervision, S.Z. and C.Z.; funding acquisition, S.Z and C.Z. All authors have read and agreed to the published version of the manuscript.
Funding
This research was jointly supported by “Deep-time Digital Earth” Science and Technology Leading Talents Team Funds for the Central Universities for the Frontiers Science Center for Deep-time Digital Earth, China University of Geosciences (Beijing) (Fundamental Research Funds for the Central Universities; grant number: 2652023001) to Shouting Zhang and basic research project of science, education and production integration pilot project of Qilu University of Technology (Shandong Academy of Sciences) (grant number: 11240455) to Cun Zhang.
Data Availability Statement
All data are contained within the work.
Acknowledgments
We are grateful to the Editor-in-Chief and the Academic Editors, as well as two anonymous reviewers for their constructive comments and suggestions that greatly improve this manuscript.
Conflicts of Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Figure 1.
(a) Generalized geological and tectonic framework of China, showing different sub-division units. The sampling locality for this study is also shown (modified after Zhang et al. [18]). (b) Geological sketch of Nephrite Jade Belts in Xinjiang, northwest China (after Liu et al. [5,6]; Tang et al. [19]). The placer nephrite jade deposits are located at Yurungkash River (White Jade River) and the Kharakash River (Black Jade River). While, the sampling area for our present study is shown in the red box.
Figure 1.
(a) Generalized geological and tectonic framework of China, showing different sub-division units. The sampling locality for this study is also shown (modified after Zhang et al. [18]). (b) Geological sketch of Nephrite Jade Belts in Xinjiang, northwest China (after Liu et al. [5,6]; Tang et al. [19]). The placer nephrite jade deposits are located at Yurungkash River (White Jade River) and the Kharakash River (Black Jade River). While, the sampling area for our present study is shown in the red box.
Figure 2.
Representative hand specimen photographs of the different types of graphite in this study: (a) The cut placer nephrite jade sample is composed of banded graphite inclusions, showing “flow” characteristics. (b) The cut black nephrite jade sample is composed of disseminated graphite inclusions. (c) Abundant of well-crystallized flaky graphite existed in placer nephrite jade. (d) Nephrite jade with weathered skins or crust shows good roundness, showing typical placer characteristics. The yellow dotted lines in Figure (a,c) represent the distribution of graphite inclusions.
Figure 2.
Representative hand specimen photographs of the different types of graphite in this study: (a) The cut placer nephrite jade sample is composed of banded graphite inclusions, showing “flow” characteristics. (b) The cut black nephrite jade sample is composed of disseminated graphite inclusions. (c) Abundant of well-crystallized flaky graphite existed in placer nephrite jade. (d) Nephrite jade with weathered skins or crust shows good roundness, showing typical placer characteristics. The yellow dotted lines in Figure (a,c) represent the distribution of graphite inclusions.
Figure 3.
Representative photomicrographs under cross-polarized light (a–c) and plane-polarized light (d–f), respectively, showing enrichments of graphite inclusions in placer nephrite jade. (a) Graphite occurs in association with tremolite and calcite. (b) Graphite occurs in association with apatite. (c) Tremolite showing porphyrioblastic texture. (d–f) Graphite inclusions occurs in random distribution in terms of flakes and spots. Tr: tremolite Cal: calcite Gr: graphite Ap: apatite Ep: epidote.
Figure 3.
Representative photomicrographs under cross-polarized light (a–c) and plane-polarized light (d–f), respectively, showing enrichments of graphite inclusions in placer nephrite jade. (a) Graphite occurs in association with tremolite and calcite. (b) Graphite occurs in association with apatite. (c) Tremolite showing porphyrioblastic texture. (d–f) Graphite inclusions occurs in random distribution in terms of flakes and spots. Tr: tremolite Cal: calcite Gr: graphite Ap: apatite Ep: epidote.
Figure 4.
The ratios Mg2+/(Mg2+ + Fe2+) vs. Si4+ are shown in red square demonstrate that the placer nephrite jade is composed only of tremolite. Tr, tremolite.
Figure 4.
The ratios Mg2+/(Mg2+ + Fe2+) vs. Si4+ are shown in red square demonstrate that the placer nephrite jade is composed only of tremolite. Tr, tremolite.
Figure 5.
Representative Raman spectra of QHL-1 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite; Cal: calcite.
Figure 5.
Representative Raman spectra of QHL-1 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite; Cal: calcite.
Figure 6.
Representative Raman spectra of QHL-2 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite.
Figure 6.
Representative Raman spectra of QHL-2 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite.
Figure 7.
Representative Raman spectra of QHL-3 nephrite jade samples, showing graphite and minor tremolite peaks. Tr: tremolite.
Figure 7.
Representative Raman spectra of QHL-3 nephrite jade samples, showing graphite and minor tremolite peaks. Tr: tremolite.
Figure 8.
Representative Raman spectra of QHL-4 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite.
Figure 8.
Representative Raman spectra of QHL-4 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite.
Figure 9.
Representative Raman spectra of QHL-5 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite.
Figure 9.
Representative Raman spectra of QHL-5 nephrite jade samples, showing graphite and tremolite peaks. Tr: tremolite.
Table 1.
Representative Electron probe microanalysis of tremolite in different black nephrite jade samples.
Table 1.
Representative Electron probe microanalysis of tremolite in different black nephrite jade samples.
| Sample Num. | QHL-1/6-5 | QHL-2/2-2 | QLH-2/2-3 | QLH-2/2-4 | QHL-3/1-1 | QHL-3/1-2 | QHL-3/1-5 | QHL-3/1-7 | QHL-3/1-11 | QHL-3/1-12 | QHL-6/1-2 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| SiO2 | 58.210 | 58.997 | 58.786 | 58.711 | 57.778 | 56.472 | 58.698 | 57.980 | 59.033 | 58.970 | 58.075 |
| Al2O3 | 0.419 | 0.434 | 0.460 | 0.387 | 0.663 | 2.218 | 0.600 | 0.954 | 0.280 | 0.247 | 0.498 |
| TiO2 | 0.039 | 0.021 | 0.004 | 0.000 | 0.068 | 0.315 | 0.000 | 0.000 | 0.071 | 0.000 | 0.000 |
| Cr2O3 | 0.000 | 0.000 | 0.000 | 0.020 | 0.018 | 0.009 | 0.000 | 0.004 | 0.000 | 0.000 | 0.025 |
| FeO | 0.392 | 0.234 | 0.223 | 0.302 | 0.628 | 0.164 | 0.487 | 0.515 | 0.306 | 0.255 | 0.487 |
| MnO | 0.026 | 0.198 | 0.152 | 0.073 | 0.033 | 0.000 | 0.059 | 0.013 | 0.192 | 0.152 | 0.073 |
| NiO | 0.015 | 0.000 | 0.000 | 0.000 | 0.000 | 0.020 | 0.000 | 0.023 | 0.018 | 0.013 | 0.000 |
| MgO | 23.852 | 24.401 | 24.348 | 24.485 | 24.617 | 24.022 | 24.111 | 24.158 | 24.260 | 24.548 | 24.325 |
| CaO | 12.867 | 12.663 | 12.951 | 12.639 | 12.249 | 13.430 | 12.254 | 13.349 | 12.679 | 12.788 | 12.309 |
| Na2O | 0.051 | 0.068 | 0.121 | 0.077 | 0.103 | 0.240 | 0.104 | 0.109 | 0.052 | 0.113 | 0.186 |
| K2O | 0.050 | 0.046 | 0.056 | 0.055 | 0.076 | 0.164 | 0.154 | 0.023 | 0.060 | 0.033 | 0.076 |
| Total | 95.921 | 97.062 | 97.101 | 96.749 | 96.233 | 97.054 | 96.467 | 97.128 | 96.951 | 97.119 | 96.054 |
| Si | 8.018 | 8.022 | 8.001 | 8.011 | 7.941 | 7.731 | 8.029 | 7.914 | 8.039 | 8.020 | 7.990 |
| Al | 0.068 | 0.070 | 0.074 | 0.062 | 0.107 | 0.358 | 0.097 | 0.153 | 0.045 | 0.040 | 0.081 |
| Ti | 0.004 | 0.002 | 0.000 | 0.000 | 0.007 | 0.032 | 0.000 | 0.000 | 0.007 | 0.000 | 0.000 |
| Cr | 0.000 | 0.000 | 0.000 | 0.002 | 0.002 | 0.001 | 0.000 | 0.000 | 0.000 | 0.000 | 0.003 |
| Fe3+ | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 | 0.000 |
| Fe2+ | 0.045 | 0.027 | 0.025 | 0.034 | 0.072 | 0.019 | 0.056 | 0.059 | 0.035 | 0.029 | 0.056 |
| Mn | 0.003 | 0.023 | 0.018 | 0.008 | 0.004 | 0.000 | 0.007 | 0.002 | 0.022 | 0.018 | 0.009 |
| Ni | 0.002 | 0.000 | 0.000 | 0.000 | 0.000 | 0.002 | 0.000 | 0.003 | 0.002 | 0.001 | 0.000 |
| Mg | 4.894 | 4.942 | 4.936 | 4.977 | 5.040 | 4.899 | 4.913 | 4.912 | 4.921 | 4.973 | 4.985 |
| Ca | 1.898 | 1.844 | 1.888 | 1.847 | 1.803 | 1.969 | 1.795 | 1.951 | 1.849 | 1.863 | 1.814 |
| Na | 0.014 | 0.018 | 0.032 | 0.020 | 0.027 | 0.064 | 0.028 | 0.029 | 0.014 | 0.030 | 0.050 |
| K | 0.009 | 0.008 | 0.010 | 0.010 | 0.013 | 0.029 | 0.027 | 0.004 | 0.010 | 0.006 | 0.013 |
| Total | 14.955 | 14.954 | 14.983 | 14.972 | 15.017 | 15.103 | 14.950 | 15.026 | 14.944 | 14.978 | 15.000 |
| Mg/(Fe + Mg) | 0.991 | 0.995 | 0.995 | 0.993 | 0.986 | 0.996 | 0.989 | 0.988 | 0.993 | 0.994 | 0.989 |
| Ca/(Ca + Na + K) | 0.988 | 0.986 | 0.978 | 0.984 | 0.978 | 0.955 | 0.971 | 0.983 | 0.987 | 0.981 | 0.966 |
| Mineral | Tremolite | Tremolite | Tremolite | Tremolite | Tremolite | Tremolite | Tremolite | Tremolite | Tremolite | Tremolite | Tremolite |
Table 2.
Representative Electron probe microanalysis of accessory minerals in different black nephrite jade samples.
Table 2.
Representative Electron probe microanalysis of accessory minerals in different black nephrite jade samples.
| Sample Num. | QHL-1/2-1 | QHL-1/6-4 | QHL-6/1-1 | QHL-1/6-7 | QHL-1/1-1 | QHL-1-1-6 | QHL-6/1-1 |
|---|---|---|---|---|---|---|---|
| SiO2 | 0.042 | 55.490 | 54.602 | 56.106 | 0.029 | 0.000 | 54.602 |
| TiO2 | 0.000 | 0.018 | 0.000 | 0.000 | 0.022 | 0.019 | 0.000 |
| Al2O3 | 0.008 | 0.259 | 0.085 | 0.176 | 0.000 | 0.000 | 0.085 |
| Cr2O3 | 0.014 | 0.025 | 0.000 | 0.032 | 0.000 | 0.023 | 0.000 |
| FeO | 0.000 | 0.052 | 0.101 | 0.196 | 0.022 | 0.000 | 0.101 |
| MnO | 0.000 | 0.040 | 0.020 | 0.000 | 0.007 | 0.040 | 0.020 |
| MgO | 0.024 | 18.620 | 18.922 | 18.213 | 12.682 | 0.855 | 18.922 |
| CaO | 52.499 | 25.216 | 25.423 | 25.291 | 41.915 | 58.270 | 25.423 |
| NiO | 0.000 | 0.000 | 0.000 | 0.020 | 0.000 | 0.000 | 0.000 |
| Na2O | 0.027 | 0.033 | 0.046 | 0.100 | 0.014 | 0.000 | 0.046 |
| K2O | 0.000 | 0.000 | 0.004 | 0.003 | 0.000 | 0.004 | 0.004 |
| Total | 52.614 | 99.753 | 99.203 | 100.137 | 54.691 | 59.211 | 99.203 |
| Mineral | Calcite | Diopside | Diopside | Diopside | Dolomite | Calcite | Diopside |
Table 3.
Representative Electron probe microanalysis of Apatite in different black nephrite jade samples.
Table 3.
Representative Electron probe microanalysis of Apatite in different black nephrite jade samples.
| Sample Num. | QHL-6/1-3 | QHL-1-6-6 | QHL-2-2-1 | QHL-1/1-3 |
|---|---|---|---|---|
| P2O5 | 42.914 | 41.928 | 42.291 | 43.858 |
| SiO2 | 0.059 | 0.084 | 0.136 | 0.048 |
| TiO2 | 0.063 | 0.037 | 0.000 | 0.000 |
| Al2O3 | 0.001 | 0.000 | 0.005 | 0.000 |
| FeO | 0.000 | 0.000 | 0.000 | 0.000 |
| MnO | 0.018 | 0.018 | 0.036 | 0.018 |
| MgO | 0.027 | 0.038 | 0.000 | 0.051 |
| CaO | 54.948 | 55.108 | 55.745 | 55.866 |
| Na2O | 0.000 | 0.031 | 0.033 | 0.038 |
| K2O | 0.009 | 0.008 | 0.001 | 0.013 |
| SO3 | 0.011 | 0.000 | 0.000 | 0.004 |
| F | 2.582 | 2.322 | 2.696 | 3.095 |
| Cl | 0.227 | 0.173 | 0.080 | 0.061 |
| Total | 99.721 | 98.730 | 99.870 | 101.735 |
| Mineral | Apatite | Apatite | Apatite | Apatite |
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Zheng, J.; Chen, L.; Zhang, C.; Liu, Y.; Tian, R.; Wu, J.; Wu, Y.; Zhang, S. Constraints on Crystallinity of Graphite Inclusions in Nephrite Jade from Xinjiang, Northwest China: Implications for Nephrite Jade Formation Temperatures. Minerals 2023, 13, 1403. https://doi.org/10.3390/min13111403
AMA Style
Zheng J, Chen L, Zhang C, Liu Y, Tian R, Wu J, Wu Y, Zhang S. Constraints on Crystallinity of Graphite Inclusions in Nephrite Jade from Xinjiang, Northwest China: Implications for Nephrite Jade Formation Temperatures. Minerals. 2023; 13(11):1403. https://doi.org/10.3390/min13111403
Chicago/Turabian StyleZheng, Jifei, Lei Chen, Cun Zhang, Yue Liu, Ruicong Tian, Jinlin Wu, Yu Wu, and Shouting Zhang. 2023. "Constraints on Crystallinity of Graphite Inclusions in Nephrite Jade from Xinjiang, Northwest China: Implications for Nephrite Jade Formation Temperatures" Minerals 13, no. 11: 1403. https://doi.org/10.3390/min13111403
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