Microdiamonds in Alkalic Dolerites from the North China Craton
-
Abstract:
Diamonds on the Earth mainly occur in volcanic rocks such as kimberlites and lamproites[1-8], but can also be found in ultrahigh-pressure metamorphic rocks[9-10], meteorites[11] and alluvial deposits[12]. In recent years, diamonds have been recovered from ophiolites[13-16] and alkalic dolerites[17-18]. The discovery of ophiolitic diamonds and alkalic dolerites diamonds has drawn significant research interests to explore the origin of this new class of diamond source and to infer the evolution of their hosting rocks[19-21]. This new type of diamond had been initially considered as a result of contamination. However, more and more evidences either directly or indirectly demonstrate that these diamonds are of natural origin[16, 18, 19, 22-24].
During a geological survey from 2012 to 2015, the geologists from Nanjing Centre of China Geological Survey discovered a large number of yellow microdiamonds in the Langan area in northern Anhui Province[18, 25-29]. The diamond-bearing rocks of these microdiamonds mainly include dolerite and olivine basalt. From 2016 to 2018, four microdiamonds in basic rocks were recovered again in the prospecting work for primary diamond deposits in the Tashan and Zhangji areas in Xuzhou, which is geographically close to Langan[30]. All these microdiamonds are similar in colour and shape to ophiolite type diamonds[31], and show different characteristics of kimberlite and lamproite type diamonds.
Cai, et al. (2019) reported the petrological characteristics of the diamondiferous rocks[17, 21, 30]. In this paper, the morphology, infrared spectrum, and carbon isotope compositions of microdiamonds were analysed and discussed by Fourier infrared spectroscopy and carbon isotope test. The types of microdiamonds found in the North China Craton, the age of mantle occurrence, and the source of carbon isotopes were revealed.
In the past, many deposits of macro-diamonds, mostly of TypeⅠ a or Ⅱ a, were found in the North China Craton, and they have been extensively studied. Microdiamonds recovered from the alkalic dolerites of the North China Craton were studied by FTIR and carbon isotopic.
These diamonds are usually light yellow to yellow, with a few colourless, and cubic, octahedral or rhomboidal dodecahedron, and octahedron in shape. The surface characteristics of diamonds, such as dissolution, can be observed. The overall N concentration is not high, with an average of 173×10-6. The infrared spectra show that most of these diamonds are Type Ⅰ b, and C centres are found at 1 344 cm-1. Three diamond samples are classified as Type Ⅰ a/Ⅰ b, because of A centres and C centres in these diamonds. Two diamonds are classified as type Ⅰ aAB because B, B′ and A centres are found co-existing. FTIR microscopic measurements from the core to the edge of the Type Ⅰ aAB diamond suggest a mantle residence time of approximately 550 Ma. The C isotopic analysis reveals that these diamonds are strongly depleted in 13C. These low δ13C values of dolerites-hosted diamonds overlap with the lower ends of peridotitic diamonds and metamorphic diamonds, and the upper end of the ophiolitic diamonds. Additionally, the reason for the strong deficit δ13C shown by the carbon isotope should be studied in the future.
-
Keywords:
- microdiamond /
- FTIR /
- carbon isotopic /
- alkalic dolerite /
- North China Craton
-
Table 1. Types of tested microdiamonds and the data of the IR spectrua
Sample No. Major Peak/cm-1 Type of C-N Type N Concentration /10-6 Ntotal/10-6 AD1 1 280, 1 344, 1 976, 2 852, 2 925 A, C ⅠaA/Ⅰb 143.0(C centre) 143.0 AD2 1 172, 1 288, 1 361, 1 650, 1 976, 1 851, 2 919 A, B', B ⅠaAB 60.9(A centre), 134.2(B centre) 195.1 AD3 1 650, 1 976, 2 850, 2 919 A Ⅰa 4.5(A centre) 4.5 AD4 1 130, 1 344, 1 976 C Ⅰb 10.7(C centre) 10.7 AD5 1 128, 1 344, 1 650, 1 976, 2 850, 2 919, 3 290 C Ⅰb 76.9(C centre) 76.9 AD5 1 130, 1 284, 1 345, 1 645, 1 977, 2 848, 2 920, 3 201, 3 394 A, C ⅠaA/Ⅰb 23.6(C centre) 23.6 AD7 1 128, 1 272, 1 344, 1 976, 2 848, 2 921 C Ⅰb 393.5(C centre) 393.5 AD8 1 128, 1 282, 1 344, 1 596, 1 976, 2 854, 2 919 A, C ⅠaA/Ⅰb 240.9(C centre) 240.9 AD9 1 344, 1 645, 1 976, 2 848, 2 919, 3 191, 3 394 C Ⅰb 137.0(C centre) 137.0 AD10 1 128, 1 272, 1 344, 1 600, 1 976, 2 848, 2 917 C Ⅰb 503.5(C centre) 503.5 -
Table 1 Types of tested microdiamonds and the data of the IR spectrua
Sample No. Major Peak/cm-1 Type of C-N Type N Concentration /10-6 Ntotal/10-6 AD1 1 280, 1 344, 1 976, 2 852, 2 925 A, C ⅠaA/Ⅰb 143.0(C centre) 143.0 AD2 1 172, 1 288, 1 361, 1 650, 1 976, 1 851, 2 919 A, B', B ⅠaAB 60.9(A centre), 134.2(B centre) 195.1 AD3 1 650, 1 976, 2 850, 2 919 A Ⅰa 4.5(A centre) 4.5 AD4 1 130, 1 344, 1 976 C Ⅰb 10.7(C centre) 10.7 AD5 1 128, 1 344, 1 650, 1 976, 2 850, 2 919, 3 290 C Ⅰb 76.9(C centre) 76.9 AD5 1 130, 1 284, 1 345, 1 645, 1 977, 2 848, 2 920, 3 201, 3 394 A, C ⅠaA/Ⅰb 23.6(C centre) 23.6 AD7 1 128, 1 272, 1 344, 1 976, 2 848, 2 921 C Ⅰb 393.5(C centre) 393.5 AD8 1 128, 1 282, 1 344, 1 596, 1 976, 2 854, 2 919 A, C ⅠaA/Ⅰb 240.9(C centre) 240.9 AD9 1 344, 1 645, 1 976, 2 848, 2 919, 3 191, 3 394 C Ⅰb 137.0(C centre) 137.0 AD10 1 128, 1 272, 1 344, 1 600, 1 976, 2 848, 2 917 C Ⅰb 503.5(C centre) 503.5 -
[1] Zhang, P. (1998). Actively explore a new type diamond primary deposit. Manag. Geol. Sci. Technol., 15: 1-8.
[2] Zhang, P. (1998). New knowledge of some important questions about diamond deposit genesis. Hunan Geol., 17: 204-210.
[3] Tappert, R., Tappert, M. C. (2011). The morphology of diamonds. In Diamonds in Nature. Springer: Berlin/Heidelberg, Germany; GmbH & Co. K: Berlin, Germany, 13-22.
[4] Tappert, R., Tappert, M. C. (2011). The origin of diamonds. In Diamonds in Nature. Springer: Berlin/Heidelberg, Germany; GmbH & Co. K: Berlin, Germany, 1-14.
[5] Murphy, K. (2014). Diamond Pipeline. SNL Metals Economics Group: Halifax, NS, Canada, 1-13.
[6] Fedortchouk, Y., McIsaac, E. (2012). Surface dissolution features on kimberlitic chromites as indicators of magmatic fluid and diamond quality. In Proceedings of the 10th International Kimberlite Conference, Bangalore, India, 5-11, 297-308.
[7] Hutchison, M. T. (2013). In diamond exploration and regional prospectivity of the northern territory of Australia. In Proceedings of the 10th International Kimberlite Conference, Bangalore, India, 5-11, 257-280.
[8] Kogarko, L. N., Ryabchikov, I. D. (2013). Diamond potential versus oxygen regime of carbonatites. Petrology, 21: 316-335. doi: 10.1134/S0869591113040048
[9] Ogasawara, Y. (2005). Microdiamonds in ultrahigh-pressure metamorphic rocks. Elements, 1: 91-96. doi: 10.2113/gselements.1.2.91
[10] Yang, J., Xu, Z., Dobrzhinetskaya, L. F., et al. (2003). Discovery of metamorphic diamonds in central China: An indication of a >4000-km-long zone of deep subduction resulting from multiple continental collisions. Terra Nova, 15: 370-379. doi: 10.1046/j.1365-3121.2003.00511.x
[11] Huss, G. R. (2005). Meteoritic nanodiamonds: Messengers from the stars. Elements, 1: 97-100. doi: 10.2113/gselements.1.2.97
[12] Tappert, R., Foden, J., Stachel, T., et al. (2009). Deep mantle diamonds from South Australia: A record of Pacific subduction at the Gondwanan margin. Geology, 37: 43-46.
[13] Yang, J., Xu, X., Li, Y., et al. (2012). Diamonds recovered from peridotite of the Purang ophiolite in the Yarlung-Zangbo suture of Tibet: A proposal for a new type of diamond occurrence. Acta Petrol. Sin., 27: 3 171-3 178.
[14] Yang, J., Xu, X., Bai, W., et al. (2014). Features of diamond in ophiolite. Acta Petrol. Sin., 30: 2 113-2 124.
[15] Rong, H., Yang, J., Zhang, Z., et al. (2013). A preliminary study of FT-IR on the diamonds from the Luobusa chromitites of Tibet and the eclogite of CCSD-MH, China. Acta Petrol. Sin., 29: 1 861-1 866.
[16] Yang, J., Wu, W., Lian, D., et al. (2021). Peridotites, chromitites and diamonds in ophiolites. Nat. Rev. Earth Environ., 2: 198-212. doi: 10.1038/s43017-020-00138-4
[17] Cai, Y., Zhang, J., Dong, Z., et al. (2018). Neoproterozoic basic magmatism in the north of Anhui Province: Evidence from whole-rock geochemistry and U-Pb geochronology of Diabase in Langan area. Geol. China, 45: 351-366.
[18] Zhang, J., Cai, Y., Dong, Z., et al. (2015). Investigation on mineral characteristic of diamond and geochemical characteristic of its host in the Langan area, Anhui Province. J. Gems Gemmol., 17: 1-11.
[19] Lian, D., Yang, J. (2019). Ophiolite-hosted diamond: A new window for probing carbon cycling in the deep mantle. Engineering, 5: 406-420. doi: 10.1016/j.eng.2019.02.006
[20] Cai, Y., Yang, X., Kang, C. (2017). Understanding of the present study of the diamond at domestic and overseas. East China Geol., 38: 95-102.
[21] Wang, X., Xiao, Y., Sun, H., et al. (2020). Initiation of the North China Craton destruction: Constraints from the diamond-bearing alkaline basalts from Lan'gan, China. Gondwana Res., 80: 228-243. doi: 10.1016/j.gr.2019.11.003
[22] Yang, J., Simakov, S. K., Moe, K., et al. (2020). Comment on "comparison of enigmatic diamonds from the Tolbachik arc volcano (Kamchatka) and Tibetan ophiolites: Assessing the role of contamination by synthetic materials" by Litasov et al. 2019. Gondwana Res., 79: 301-303. doi: 10.1016/j.gr.2019.09.010
[23] Lian, D., Yang, J., Wiedenbeck, M., et al. (2018). Carbon and nitrogen isotope, and mineral inclusion studies on the diamonds from the Pozanti-Karsanti chromitite, Turkey. Contrib. Mineral. Petrol., 173: 72. doi: 10.1007/s00410-018-1499-5
[24] Howell, D., Griffin, W. L., Yang, J., et al. (2015). Diamonds in ophiolites: Contamination or a new diamond growth environment? Earth Planet. Sci. Lett., 430: 284-295. doi: 10.1016/j.epsl.2015.08.023
[25] Cai, Y., Xu, M., Shi, J., et al. (2019). Mineral chemistry characteristics of clinopyroxene and ilmenite in basite of Langan area, northern Anhui Province. Geol. Bull. China, 38: 1-13.
[26] Cai, Y., Zhang, J., Kang, C., et al. (2019). Mineral chemistry characteristics of garnets in diamondiferous basite of Langan area, Anhui Province. Geol. Bull. China, 38: 18-28.
[27] Zhang, J., Lu, F., Cai, Y. (2016). Characteristic of alkali-basic rock type diamond ore's Remote Sensing in the Langan area, Anhui province. J. Gems Gemmol., 19: 1-9.
[28] Cai, Y., Chen, G., Zhang, J., et al. (2014). Geochemical features of the olivine-gabbros and its relationship with diamond-forming in the Langan area, Anhui province. Resour. Surv. Environ., 35: 245-253.
[29] Zhuang, J. (2013). Study of magnetic anomaly features and its implications for diamond exploration in the Langan-Chualan area, Suzhou City. Geol. Anhui, 23: 123-125.
[30] Cai, Y., Shi, J., Zhou, Q., e al. (2021). Study on the geochemistry of the diamondiferous olivine basalt and magma evolution in Bailushan area, Xuzhou. China Geol., 48: 1 850-1 864.