瓦茲利石

瓦茲利石
瓦茲利石
基本資料
類別	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
性質
顏色	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
光學性質	二轴晶
折射率	n = 1.76

瓦茲利石（英語：Wadsleyite）^[1]是一種斜方晶系礦物，分子式為 ${\ce {\beta -(Mg,Fe)2SiO4}}$ 。在加拿大艾伯塔省的皮斯河隕石中被發現，為橄欖石 ${\ce {\alpha -(Mg,Fe)2SiO4}}$ 在增加壓力下相變而成，並隨著壓力增加最終轉變為尖晶石結構的尖晶橄欖石( ${\ce {\gamma -(Mg,Fe)2SiO4}}$ ) ^[2]。其晶胞參數約為：

a = 5.7 Å

b = 11.71 Å

c = 8.24 Å^[3]

瓦茲利石於1966年由Ringwood和Major首次發現，於1968年被Akimoto和Sato確認為穩定相^[4]，該相最初被稱為 ${\ce {\beta -Mg2SiO4}}$ 或「β相」。Wadsleyite以礦物學家 Arthur David Wadsley（1918年-1969年）的名字命名。

組成

純鎂質的瓦茲利石，按氧化物的重量百分比為 42.7% ${\ce {SiO2}}$ 和 57.3% ${\ce {MgO}}$ 。瓦茲利石中的微量元素包括：銣 (Rb)、鍶 (Sr)、鋇 (Ba)、鈦 (Ti)、鋯 (Zr)、鈮 (Nb)、鉿 (Hf)、鉭 (Ta)、釷 (Th) 和鈾 (U) ^[5]。這些元素的濃度可能比地球上地幔過渡帶中假設的濃度要大。此外，這些分析結果有助於了解地球內部的化學分異和岩漿作用^[6]。雖然分子式是無水的，但瓦茲利石可以包含超過3%（重量）的 ${\ce {H2O}}$ ^[7]。

成因及產狀

瓦茲利石是在加拿大艾伯塔省和平河的L6超鉛橄欖石球粒隕石中發現的。據信，該瓦茲利石是在隕石撞擊地球時，由隕石内富硫化物脈中的橄欖石在高壓下形成的。呈微晶岩石碎片，直徑通常不超過0.5毫米。瓦茲利石的伴生礦物有尖晶橄榄石、橄榄石、斜方辉石、斜长石、陨硫铁^[8]。

瓦茲利石在地幔過渡帶的上部（深度410-520 公里之間）為穩定相，由於在瓦茲利石分子結構 ${\ce {Si2O7}}$ 中的氧原子未與硅完全結合，因此一些氧原子很容易和氫結合成水，從而使礦物中含有高濃度的氫原子。由於此種未鍵合的氧原子具低靜電勢。含水瓦茲利石被認為是地幔中儲水的潛在場所^[7]。儘管瓦茲利石在其化學式中不含氫(H)，但它可能含有超過3%（重量）的 ${\ce {H2O}}$ ，並且可能在過渡區壓力－溫度條件下與含水熔體共存，水的溶解度和瓦茲利石的密度取決於地球的溫度和壓力。根據正常地熱梯度，瓦茲利石的最大儲水能力可能會沿降低至約0.5-1 wt%^[9]。

参见

以人名命名的矿物列表

參考文獻

^ 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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