瓦兹利石

瓦兹利石
瓦兹利石
基本资料
类别	双硅酸盐矿物
化学式	Mg2SiO4
晶体分类	斜方双锥晶类
晶体空间群	Imma
晶胞	a = 5.7 Å, b = 11.71 Å ; c = 8.24 Å; Z = 8
性质
颜色	浅灰棕色
晶体惯态	呈显微晶质集合体
晶系	正交晶系
比重	3.84
光学性质	二轴晶
折射率	n = 1.76

瓦兹利石（英语：Wadsleyite）^[1]是一种斜方晶系矿物，分子式为 ${\ce {\beta -(Mg,Fe)2SiO4}}$ 。在加拿大艾伯塔省的皮斯河陨石中被发现，为橄榄石 ${\ce {\alpha -(Mg,Fe)2SiO4}}$ 在增加压力下相变而成，并随着压力增加最终转变为尖晶石结构的尖晶橄榄石( ${\ce {\gamma -(Mg,Fe)2SiO4}}$ ) ^[2]。其晶胞参数约为：

a = 5.7 Å

b = 11.71 Å

c = 8.24 Å^[3]

瓦兹利石于1966年由Ringwood和Major首次发现，于1968年被Akimoto和Sato确认为稳定相^[4]，该相最初被称为 ${\ce {\beta -Mg2SiO4}}$ 或“β相”。Wadsleyite以矿物学家 Arthur David Wadsley（1918年-1969年）的名字命名。

组成

纯镁质的瓦兹利石，按氧化物的重量百分比为 42.7% ${\ce {SiO2}}$ 和 57.3% ${\ce {MgO}}$ 。瓦兹利石中的微量元素包括：铷 (Rb)、锶 (Sr)、钡 (Ba)、钛 (Ti)、锆 (Zr)、铌 (Nb)、铪 (Hf)、钽 (Ta)、钍 (Th) 和铀 (U) ^[5]。这些元素的浓度可能比地球上地幔过渡带中假设的浓度要大。此外，这些分析结果有助于了解地球内部的化学分异和岩浆作用^[6]。虽然分子式是无水的，但瓦兹利石可以包含超过3%（重量）的 ${\ce {H2O}}$ ^[7]。

成因及产状

瓦兹利石是在加拿大艾伯塔省和平河的L6超铅橄榄石球粒陨石中发现的。据信，该瓦兹利石是在陨石撞击地球时，由陨石内富硫化物脉中的橄榄石在高压下形成的。呈微晶岩石碎片，直径通常不超过0.5毫米。瓦兹利石的伴生矿物有尖晶橄榄石、橄榄石、斜方辉石、斜长石、陨硫铁^[8]。

瓦兹利石在地幔过渡带的上部（深度410-520 公里之间）为稳定相，由于在瓦兹利石分子结构 ${\ce {Si2O7}}$ 中的氧原子未与硅完全结合，因此一些氧原子很容易和氢结合成水，从而使矿物中含有高浓度的氢原子。由于此种未键合的氧原子具低静电势。含水瓦兹利石被认为是地幔中储水的潜在场所^[7]。尽管瓦兹利石在其化学式中不含氢(H)，但它可能含有超过3%（重量）的 ${\ce {H2O}}$ ，并且可能在过渡区压力－温度条件下与含水熔体共存，水的溶解度和瓦兹利石的密度取决于地球的温度和压力。根据正常地热梯度，瓦兹利石的最大储水能力可能会沿降低至约0.5-1 wt%^[9]。

参见

以人名命名的矿物列表

参考文献

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ Tokár, Kamil; Jochym, Paweł T.; Piekarz, Przemysław; Łażewski, Jan; Sternik, Małgorzata; Parlinski, Krzysztof (2013). "Thermodynamic properties and phase stability of wadsleyite II". Physics and Chemistry of Minerals. 40 (3): 251–257. Bibcode:2013PCM....40..251T. doi:10.1007/s00269-013-0565-9. ISSN 0342-1791.
^ Mindat.org
^ Akimoto, Syun-iti; Sato, Yosiko (1968). "High-pressure transformation in Co2SiO4 olivine and some geophysical implications". Physics of the Earth and Planetary Interiors. 1 (7): 498–504. Bibcode:1968PEPI....1..498A. doi:10.1016/0031-9201(68)90018-6. ISSN 0031-9201.
^ Webmineral data
^ Mibe, Kenji; Orihashi, Yuji; Nakai, Shun'ichi; Fujii, Toshitsugu (2006). "Element partitioning between transition-zone minerals and ultramafic melt under hydrous conditions". Geophysical Research Letters. 33 (16). Bibcode:2006GeoRL..3316307M. doi:10.1029/2006gl026999. ISSN 0094-8276.
^ ^7.0 ^7.1 Inoue, Toru; Yurimoto, Hisayoshi; Kudoh, Yasuhiro (1995). "Hydrous modified spinel, Mg1.75SiH0.5O4: A new water reservoir in the mantle transition region". Geophysical Research Letters. 22 (2): 117–120. Bibcode:1995GeoRL..22..117I. doi:10.1029/94gl02965. ISSN 0094-8276.
^ Price, Geoffrey D. (1983). "The nature and significance of stacking faults in wadsleyite, natural β-(Mg, Fe)2SiO4 from the Peace River meteorite". Physics of the Earth and Planetary Interiors. 33 (2): 137–147. Bibcode:1983PEPI...33..137P. doi:10.1016/0031-9201(83)90146-2. ISSN 0031-9201.
^ Ohtani, Eiji; Litasov, Konstantin; Hosoya, Tomofumi; Kubo, Tomoaki; Kondo, Tadashi (2004). "Water transport into the deep mantle and formation of a hydrous transition zone". Physics of the Earth and Planetary Interiors. 143–144: 255–269. Bibcode:2004PEPI..143..255O. doi:10.1016/j.pepi.2003.09.015. ISSN 0031-9201.

[”1”-1] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.

[”1a”-2] Tokár, Kamil; Jochym, Paweł T.; Piekarz, Przemysław; Łażewski, Jan; Sternik, Małgorzata; Parlinski, Krzysztof (2013). "Thermodynamic properties and phase stability of wadsleyite II". Physics and Chemistry of Minerals. 40 (3): 251–257. Bibcode:2013PCM....40..251T. doi:10.1007/s00269-013-0565-9. ISSN 0342-1791.

[”1b”-3] Mindat.org

[”7”-4] Akimoto, Syun-iti; Sato, Yosiko (1968). "High-pressure transformation in Co2SiO4 olivine and some geophysical implications". Physics of the Earth and Planetary Interiors. 1 (7): 498–504. Bibcode:1968PEPI....1..498A. doi:10.1016/0031-9201(68)90018-6. ISSN 0031-9201.

[”8a”-5] Webmineral data

[”8”-6] Mibe, Kenji; Orihashi, Yuji; Nakai, Shun'ichi; Fujii, Toshitsugu (2006). "Element partitioning between transition-zone minerals and ultramafic melt under hydrous conditions". Geophysical Research Letters. 33 (16). Bibcode:2006GeoRL..3316307M. doi:10.1029/2006gl026999. ISSN 0094-8276.

[”9”-7] 7.0 ^7.1 Inoue, Toru; Yurimoto, Hisayoshi; Kudoh, Yasuhiro (1995). "Hydrous modified spinel, Mg1.75SiH0.5O4: A new water reservoir in the mantle transition region". Geophysical Research Letters. 22 (2): 117–120. Bibcode:1995GeoRL..22..117I. doi:10.1029/94gl02965. ISSN 0094-8276.

[”10”-8] Price, Geoffrey D. (1983). "The nature and significance of stacking faults in wadsleyite, natural β-(Mg, Fe)2SiO4 from the Peace River meteorite". Physics of the Earth and Planetary Interiors. 33 (2): 137–147. Bibcode:1983PEPI...33..137P. doi:10.1016/0031-9201(83)90146-2. ISSN 0031-9201.

[”6”-9] Ohtani, Eiji; Litasov, Konstantin; Hosoya, Tomofumi; Kubo, Tomoaki; Kondo, Tadashi (2004). "Water transport into the deep mantle and formation of a hydrous transition zone". Physics of the Earth and Planetary Interiors. 143–144: 255–269. Bibcode:2004PEPI..143..255O. doi:10.1016/j.pepi.2003.09.015. ISSN 0031-9201.

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