Mid-Ocean ridge peridotites revisited: homogeneity/heterogeneity and the nature of the Oceanic plate

• Project/Area Number: 26287134
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Kanazawa University
• Principal Investigator: Morishita Tomoaki 金沢大学, 自然システム学系, 教授 (80334746)
• Co-Investigator(Kenkyū-buntansha): 仙田 量子 国立研究開発法人海洋研究開発機構, 地球内部物質循環研究分野, 研究員 (50377991) ; 浜田 盛久 (濱田 盛久) 国立研究開発法人海洋研究開発機構, 地球内部物質循環研究分野, 研究員 (60456853) ; 鈴木 勝彦 国立研究開発法人海洋研究開発機構, 海底資源研究開発センター, グループリーダー (70251329) ; 針金 由美子 国立研究開発法人産業技術総合研究所, 地質情報研究部門, 研究員 (90569360)
• Co-Investigator(Renkei-kenkyūsha): TAMURA Akihiro 金沢大学, 自然システム学系, 博士研究員 (80401884)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥15,860,000 (Direct Cost: ¥12,200,000、Indirect Cost: ¥3,660,000); Fiscal Year 2016: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000); Fiscal Year 2015: ¥5,330,000 (Direct Cost: ¥4,100,000、Indirect Cost: ¥1,230,000); Fiscal Year 2014: ¥5,980,000 (Direct Cost: ¥4,600,000、Indirect Cost: ¥1,380,000)
• Keywords: 海洋プレート / 海洋マントル / 部分溶融 / かんらん岩 / マントルかんらん岩 / 再肥沃化 / 島弧下マントル / 交代作用 / 中央海嶺 / マントル / 物質循環 / メルトーマントル反応 / モホ面 / 元素循環 / 深海性かんらん岩 / 地殻物質リサイクリング / モホ / マントル掘削

Outline of Final Research Achievements

Results of this research on the sub-oceanic mantle peridotites are summarized as follows. 1)　We suggested possibility of existence of ancient melted residue in abyssal peridotites recovered from mid-ocean ridge system (Indian Ocean) and its “crustallization” processes by melt-residual peridotite interactions. Addition to this, melting processes selectively accumulated ancient melting geochemical signatures by melt-rock interactions. 2) We clarified mid-ocean ridge type peridotite origin for mantle section of the Eastern end of the Jurassic-Cretaceous ophiolite belt (Tethys ophiolite belt), Andaman Ophiolite, and its modification at subduction setting during the initiation of subduction. 3) We examined back-arc magmatic processes deduced from peridotite xenolith in back arc region (Japan Sea). Our results suggest that the late stage of magma process is similar to those expected beneath Mid-ocean ridge setting, resulting in the similar depleted peridotites in both tectonic settings.

Research Products

• [Int'l Joint Research] University of Culcutta(インド)
• [Int'l Joint Research] University of Pavia(イタリア)
• [Int'l Joint Research] Tanta University(エジプト)
• [Int'l Joint Research] University of Hawaii(USA)
• [Int'l Joint Research]
• [Journal Article] Reaction microtextures in entrapped xenoliths in alkali basalts from the Deccan large igneous province, India: Implications to the origin and evolution (2017)
  • Author(s): Chattopadhaya, S., Ghosh, B., Morishita, T., Nandy, S., Tamura, A., Bandyopadhyay, D.,
  • Journal Title: Journal of Asian Earth Sciences Volume: 138 Pages: 291-305
  • DOI: 10.1016/j.jseaes.2017.01.028
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] 古い海洋プレートの沈み込み直前での屈曲断層形成に伴う加水作用解明に向けた海洋掘削計画概要 (2017)
  • Author(s): 森下知晃・藤江 剛・山野 誠・中西正男・尾鼻浩一郎・中村恭之・斎藤実篤・小平秀一・木村純一・黒田潤一郎・小野重明
  • Journal Title: 地学雑誌 Volume: -
  • NAID: 130005696815
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] 中央海嶺産海洋プレート深部起源岩石掘削の成果と展望 (2017)
  • Author(s): 森下知晃
  • Journal Title: 地質学雑誌 Volume: -
  • NAID: 130005858673
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Mantle hornblendites of Naein ophiolite (Central Iran): Evidence of deep high temperature hydrothermal metasomatism in an upper mantle section (2017)
  • Author(s): Torabi, G., Arai, S., Morishita, T., Tamura, A.
  • Journal Title: Petrology Volume: 25 Pages: 114-137
  • DOI: 10.1134/s0869591117010076
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Adakite metasomatism in a back-arc mantle peridotite xenolith from the Sea of Japan (2017)
  • Author(s): Ichiyama, Y., Morishita, T., Tamura, A., Arai, S.
  • Journal Title: American Mineralogist Volume: 102 Pages: 341-346
  • DOI: 10.2138/am-2017-5720
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Chapter 7 Andaman?Nicobar Ophiolites, India: origin, evolution and emplacement (2017)
  • Author(s): Ghosh, B., Bandyopadhyay, B., Morishita, T.
  • Journal Title: Geological Society, London, Memoirs Volume: 47 Pages: 95-110
  • DOI: 10.1144/m47.7
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Ancient Melting Residual Peridotites Producing Variable Source Mantle beneath Mid-ocean Ridges: Detection and Geodynamic Implications (2016)
  • Author(s): 森下知晃
  • Journal Title: J. Geogr. Volume: 124 Issue: 3 Pages: 333-354
  • DOI: 10.5026/jgeography.124.333
  • NAID: 130005087139
  • Year and Date: 2016-03-16
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Peridotite xenoliths from the Shiribeshi Seamount, Japan Sea: insights into mantle processes in a back-arc basin (2016)
  • Author(s): Ichiyama, Y., Morishita, T., Tamura, A., Arai, S.
  • Journal Title: Contributions to Mineralogy and Petrology Volume: 171 Pages: 86-86
  • DOI: 10.1007/s00410-016-1300-6
  • Peer Reviewed
• [Journal Article] Compositional variations in spinel-hosted pargasite inclusions in the olivine-rich rock from the oceanic crust?mantle boundary zone (2016)
  • Author(s): Tamura, A., Morishita, T., Ishimaru, S., Hara, K., Sanfilippo, A., Arai, S.
  • Journal Title: Contributions to Mineralogy and Petrology Volume: XX Pages: 39-39
  • DOI: 10.1007/s00410-016-1245-9
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Melt-rock interactions and fabric development of peridotites from North Pond in the Kane area, Mid-Atlantic Ridge: Implications of microstructural and petrological analyses of peridotite samples from IODP Hole U1382A (2016)
  • Author(s): Harigane Y., Abe N., Michibayashi K., Kimura J.-I., and Chang Q.
  • Journal Title: Geochemistry, Geophysics, Geosystems Volume: 17 Pages: 1-15
  • DOI: 10.1002/2016gc006429
  • Peer Reviewed / Open Access / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Ancient depleted mantle as a source of boninites in the Izu-Bonin-Mariana arc: evidence from Os isotopes in Cr-spinel and magnetite (2016)
  • Author(s): R. Senda, K. Shimizu, and K. Suzuki
  • Journal Title: Chemical Geology Volume: 439 Pages: 110-119
  • DOI: 10.1016/j.chemgeo.2016.06.018
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Andaman-Nicobar ophiolites, India: Origin, Evolution and Emplacement (2016)
  • Author(s): Biswajit, G., Bandyopadhyay, B., Morishita, T.
  • Journal Title: Journal of Geological Society of London Volume: xx
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Rhenium-osmium isotope fractionateon at the oceanic crust-mantle boundary (2016)
  • Author(s): Sanfilippo, A., Morishita, T., Senda, R.
  • Journal Title: Geology Volume: 44 Pages: 167-170
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Hybrid troctolites from Mid-Ocean Ridges: inherited mantle in the lower crust (2015)
  • Author(s): Sanfilippo, A., Morishita, T., Kumagai, H., Okino, K., Hara, K., Tamura, A., Arai, S.
  • Journal Title: Lithos Volume: 232 Pages: 124-130
  • DOI: 10.1016/j.lithos.2015.06.025
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Measurement of whole-rock trace-element composition by flux-free fused glass and LA-ICP-MS: evaluation of simple and rapid routine work (2015)
  • Author(s): Tamura, A., Akizawa, N., Otsuka, R., Kanayama, K., Python, M., Morishita, T., Arai, S.
  • Journal Title: GEOCHEMICAL JOURNAL Volume: 49 Issue: 3 Pages: 233-241
  • DOI: 10.2343/geochemj.2.0353
  • NAID: 130005074561
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] A record of spontaneous subduction initiation in the Izu-Bonin-Mariana arc (2015)
  • Author(s): Arculus, R.J., Ishizuka, O., Bogus, K.A., Gurnis, M., Hickey-Vargas, R., Aljahdali, M.H., Bandini-Maeder, A.N., Barth, A.P., Brandl, P.A., Drab, L., do Monte Guerra, R., Hamada, M., et al.
  • Journal Title: Nature Geoscience Volume: 8 Pages: 728-733
  • DOI: 10.1038/ngeo2515
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Geochemistry of spinel-hosted amphibole inclusions in abyssal peridotite: insight into secondary melt formation in melt- peridotite reaction. (2014)
  • Author(s): Tamura, A., Morishira, T., Ishimaru, S. and Arai. S.
  • Journal Title: Contributions to Mineralogy and Petrology Volume: 167 Pages: 1-16
  • DOI: 10.1007/s00410-014-0974-x
  • Peer Reviewed
• [Journal Article] Grain-scale plastic deformation of chromite from podiform chromitite of the Naga-Manipur ophiolite belt, India; Implication to mantle dynamics (2014)
  • Author(s): Ghosh, B., Ray, J., Morishita, T.
  • Journal Title: Ore Geology Reviews Volume: 56 Pages: 199-208
  • DOI: 10.1016/j.oregeorev.2013.09.001
  • Peer Reviewed
• [Journal Article] Moho Transition Zone in the Cretaceous Andaman ophiolite, India: a passage from the mantle to the crust. (2014)
  • Author(s): Ghosh, B., Morishita, T., Gupta, B.S., Tamura, A., Arai, S. and Bandyopadhyay, D.
  • Journal Title: Lithos Volume: 198-199 Pages: 117-128
  • DOI: 10.1016/j.lithos.2014.03.027
  • Peer Reviewed
• [Journal Article] Polybaric crystallization differentiation of H2O-saturated island arc low-K tholeiite magmas: A case study of the Izu-Oshima volcano in the Izu arc (2014)
  • Author(s): Hamada Morihisa, Okayama Yuko, Kaneko Takayuki, Yasuda Atsushi and Fujii Toshitsugu
  • Journal Title: Earth, Planets and Space Volume: 66 Pages: 15-15
  • DOI: 10.1186/1880-5981-66-15
  • URL: http://www.jamstec.go.jp/jir/infolib/meta_pub/detail-jp
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] Volatile (F and Cl) concentrations in Iwate olivine-hosted melt inclusions indicating low-temperature subduction (2014)
  • Author(s): Estelle Rose-Koga, Kenneth Koga, Morihisa Hamada, Thomas Helois, Martin Whitehouse and Nobumichi Shimizu
  • Journal Title: Earth, Planets and Space Volume: 66 Pages: 81-81
  • DOI: 10.1186/1880-5981-66-81
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] Water content in arc basaltic magma in the Northeast Japan and Izu arcs: an estimate from Ca/Na partitioning between plagioclase and melt (2014)
  • Author(s): Ushioda, M., Takahashi,E., Hamada, M., and Suzuki, T.
  • Journal Title: Earth, Planets and Space Volume: 66 Pages: 1-10
  • DOI: 10.1186/1880-5981-66-127
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] Re-evaluating digestion methods for highly siderophile element and 187Os isotope analysis: Evidence from geological reference materials (2014)
  • Author(s): Ishikawa, A., Senda, R., Suzuki, K., Dale, C. W., Meisel, T.
  • Journal Title: Chemical Geology Volume: 384 Pages: 27-46
  • DOI: 10.1016/j.chemgeo.2014.06.013
  • Peer Reviewed
• [Journal Article] Microstructures, composition, and seismic properties of the Ontong Java Plateau mantle root (2014)
  • Author(s): Tommasi, A., Ishikawa, A.
  • Journal Title: Geochemistry, Geophysics, Geosystems Volume: 15 Pages: 4547-4569
  • DOI: 10.1002/2014gc005452
  • Peer Reviewed / Open Access
• [Presentation] Petrogenesis of serpentinized peridotites from the northern Mariana forearc area (2016)
  • Author(s): Harigane, Y., Ishizuka, O., Maekawa, H., Ghosh, T. And Snow, J. E.
  • Organizer: American Geophysical Union
  • Place of Presentation: Moscone Center (San Francisco, USA)
  • Year and Date: 2016-12-12
  • Int'l Joint Research
• [Presentation] Petrology and geochemistry of the Central Indian Ridge Peridotites: Ridge processes and prehistory (2016)
  • Author(s): Morishita, T. and Senda, R.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research
• [Presentation] Subduction initiation deduced from peridotites of the Izu-Bonin-Mariana Forearc and ophiolites: impolications for ARC MOHO diversity (2016)
  • Author(s): Morishita, T.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research / Invited
• [Presentation] Microstructural and Petrological Analyses Peridotites and Gabbros from IODP Hole U1382A at North Pond in the Kane Area of Mid-Atlantic Ridge (2016)
  • Author(s): Harigane, Y., Abe, N., Michibayashi, K., Kimura, J. and Chang, Q.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research / Invited
• [Presentation] IODP Exp.351 Izu-Bonin-Mariana Arc Origins: Refertilization of Mantle Inferred from Melt Inclusion (2016)
  • Author(s): Hamada, M., Brandl, P.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research / Invited
• [Presentation] Diffusive Infiltration of Hydrogen into Plagioclase Xenocryst Taken by H2O-Rich Rear-Arc Basaltic Melt (2016)
  • Author(s): Hamada, M.
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research
• [Presentation] PGE Signature of an EM-1 Mantle Source, Evidence from Pitcairn Basalts (2016)
  • Author(s): Senda R, Ishikawa A, Hanyu T, Kawabata H, Takahashi T & Suzuki K
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research
• [Presentation] Mantle Origin of Natural Polycrystalline Diamond, Carbonado, Inferred from Inclusion Chemistry (2016)
  • Author(s): Kagi H, Shiraishi N, Senda R, Suzuki K, Asano N & Ohfuji H
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research / Invited
• [Presentation] Re-Os Isotope and Highly Siderophile Element Constraints on the Origin of Ancient Depleted Domains in the Modern Convecting Mantle (2016)
  • Author(s): Ishikawa A, Senda R, Tani K-I, Suzuki K & Ishii T
  • Organizer: Goldschmidt Conference
  • Place of Presentation: Pacifico Yokohama (Yokohama, Japan)
  • Int'l Joint Research
• [Presentation] 北極海ガッケル海嶺かんらん岩の記載岩石学 (2016)
  • Author(s): 橋本 諭，森下 知晃，田村 明弘，曽田 祐介
  • Organizer: 日本鉱物科学会年会
  • Place of Presentation: 金沢大学（金沢市，日本）
• [Presentation] Os同位体比と白金族元素から見たEM-1成分の由来 (2016)
  • Author(s): 仙田 量子、石川 晃、羽生 毅、川畑 博、高橋 俊郎、鈴木 勝彦
  • Organizer: 地球惑星科学連合大会
  • Place of Presentation: 幕張メッセ（千葉市、日本）
• [Presentation] IODP Exp. 360速報：南西インド洋海海嶺、超低速拡大海域の下部地殻;モホ掘削 (SloMo) (2016)
  • Author(s): ディック ヘンリー、マックレオド クリストファー、ブルム ピーター、*阿部 なつ江、森下 知晃、野坂 俊夫、サンフィリッポ アレッシオ、IODP Exp.360 乗船研究者
  • Organizer: 地球惑星科学連合大会
  • Place of Presentation: 幕張メッセ（千葉市、日本）
• [Presentation] Osmium isotope variations in the Pacific mantle: implications for the distribution of heterogeneity in the convecting mantle. (2015)
  • Author(s): Ishikawa, A., Senda, R. Suzuki, K., Tani, K., Ishii, T.
  • Organizer: American Geophysical Union
  • Place of Presentation: San Francisco, USA
  • Year and Date: 2015-12-12
  • Int'l Joint Research / Invited
• [Presentation] IODP Expedition 351 Izu- Bonin-Mariana Arc Origins: Temporal evolution of arc volcanism inferred from melt inclusions (2015)
  • Author(s): Hamada, M., Brandl, P.A., IODP Exp.351 Scientists
  • Organizer: American Geophysical Union
  • Place of Presentation: San Francisco, USA
  • Year and Date: 2015-12-12
  • Int'l Joint Research
• [Presentation] インド洋中央海嶺の深海性かんらん岩：マントルの不均質性と海洋プレート形成への影響 (2015)
  • Author(s): 森下知晃，仙田量子，曽田祐介，伊藤加寿也，中村謙太郎，熊谷英憲，沖野郷子，佐藤暢
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 幕張
  • Year and Date: 2015-05-23
• [Presentation] Investigation into hydrology along bending-induced faults by off-Tohoku incoming plate sampling (2015)
  • Author(s): Morishita, T., Morgan, J.P., Fujie, G., Abe, N, Ono, S.,
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 幕張
  • Year and Date: 2015-05-23
• [Presentation] Maturing processes of ARC MOHO deduced from the Izu-Bonin and Ophiolites and implications for economic chromitite formations (2015)
  • Author(s): Morishita, T.
  • Organizer: The 11nd International Conference for Geosciences, Riyadh, Saudi Arabia
  • Place of Presentation: Riyadh, Saudi Arabia
  • Year and Date: 2015-05-12
  • Int'l Joint Research / Invited
• [Presentation] Back-arc mantle evolution inferred from Peridotite Xenoliths from the Japan Sea (2014)
  • Author(s): Morishita, T., Ichiyama, Y., Tamura, A. and Arai, S.,
  • Organizer: American Geophysical Union
  • Place of Presentation: San Francisco
  • Year and Date: 2014-12-19
• [Presentation] Insight into the uppermost mantle section of nascent arc (2014)
  • Author(s): Morishita, T., Tani, K., Dilek, Y., Tamura, A. and Arai, S.
  • Organizer: Ophiolite Symposium
  • Place of Presentation: Damghan, Iran
  • Year and Date: 2014-09-18
  • Invited
• [Presentation] Example from harzburgite in Izu-Bonin forearc area (2014)
  • Author(s): Harigane, Y., Michibayashi, K., Morishita, T., Dick, H.J.B., Ishiduka, O.
  • Organizer: Ophiolite Symposium
  • Place of Presentation: Damghan, Iran
  • Year and Date: 2014-09-18
  • Invited
• [Presentation] オスミウム同位体比と白金族元素組成から見た海洋プレー ト下部地殻トロクトライトの形成 (2014)
  • Author(s): Ryoko Senda, Akira Ishikawa, Tomoaki Morishita, Katsuhiko Suzuki, Teruaki Ishii
  • Organizer: 日本地球化学会年会
  • Place of Presentation: 富山
  • Year and Date: 2014-09-16 – 2014-09-18
• [Presentation] マントル融解過程に伴う強親鉄性元素の挙動 (2014)
  • Author(s): 石川晃
  • Organizer: 資源地質学会第64回年会学術講演会
  • Place of Presentation: 東京都
  • Year and Date: 2014-06-25 – 2014-06-27
  • Invited
• [Presentation] Petrological evidence for arc-metasomatized peridotites beneath the mid-ocean ridges (2014)
  • Author(s): Morishita, T.
  • Organizer: 6th Orogenic Lherzolite Coference
  • Place of Presentation: Marrakesh, Morocco
  • Year and Date: 2014-05-09
• [Presentation] Osmium isotope heterogeneity in the Pacific uppermost mantle (2014)
  • Author(s): Ishikawa, A., Senda, R., Tani, K., Suzuki, K., Ishii, T.
  • Organizer: 6th International Orogenic Lherzolite Conference
  • Place of Presentation: Marrakech, Morocco.
  • Year and Date: 2014-05-09
• [Presentation] PGE abundances and Os isotope ratios of troctolite from the Pacific oceanic lithosphere (2014)
  • Author(s): Ryoko Senda, Akira Ishikawa, Tomoaki Morishita, Katsuhiko Suzuki, Teruaki Ishii
  • Organizer: 6th International Orogenic Lherzolite Conference
  • Place of Presentation: Marrakech, Morocco.
  • Year and Date: 2014-05-09
• [Presentation] 中央海嶺下に存在する島弧マントル物質の物質学的証拠 (2014)
  • Author(s): 森下知晃・仙田量子・鈴木勝彦・中村謙太郎・佐藤暢・沖野郷子
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 横浜
  • Year and Date: 2014-04-28
• [Presentation] H2Oに飽和した島孤ソレアイトマグマの結晶分化作用：伊豆大島火山における事例研究 (2014)
  • Author(s): 浜田盛久，岡山悠子，金子隆之，安田敦，藤井敏嗣
  • Organizer: 日本地球惑星科学連合大会
  • Place of Presentation: 横浜
  • Year and Date: 2014-04-28
• [Book] Subseafloor Biosphere Linked to Hydrothermal Systems: TAIGA Concept (2015)
  • Author(s): Morishita, T., Nakamura, K., Shibuya, T., Kumagai, H., Sato, T., Okino, K., Sato, H., Nauchi, R., Hara, K. and Takamaru, R.
  • Total Pages: 666
  • Publisher: Springer
• [Book] Subseafloor Biosphere Linked to Hydrothermal Systems: TAIGA Concept (2015)
  • Author(s): Morishita, T., Nakamura, K., Shibuya, T., Kumagai, H., Sato, T., Okino, K., Sato, H., Nauchi, R., Hara, K. and Takamaru, R
  • Total Pages: 666
  • Publisher: Springer