{"created":"2021-03-01T06:09:12.503053+00:00","id":5355,"links":{},"metadata":{"_buckets":{"deposit":"5f0e2679-d4c3-4538-bdd8-3038f750757b"},"_deposit":{"id":"5355","owners":[],"pid":{"revision_id":0,"type":"depid","value":"5355"},"status":"published"},"_oai":{"id":"oai:niigata-u.repo.nii.ac.jp:00005355","sets":["453:455","468:563:564"]},"item_6_alternative_title_1":{"attribute_name":"その他のタイトル","attribute_value_mlt":[{"subitem_alternative_title":"海洋地殻中に発達した島弧地殻の最初期形成プロセス : オマーンオフィオライトにおける後期貫入岩類の地質学、地球化学、地質年代学的研究"}]},"item_6_biblio_info_6":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"2013-03-25","bibliographicIssueDateType":"Issued"},"bibliographicPageEnd":"154","bibliographicPageStart":"1","bibliographic_titles":[{}]}]},"item_6_date_granted_51":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2013-03-25"}]},"item_6_degree_grantor_49":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_name":"新潟大学"}]}]},"item_6_degree_name_48":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（理学）"}]},"item_6_description_4":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"本研究では中東アラビア半島北東部に露出するオマーンオフィオライトの北部、Fizh 岩体北部地域（Rajmi地域）において、南北25km、東西12kmの範囲で斑れい岩質下部地殻部における地質図の作成を行い、後期貫入岩類を対象に記載岩石学、地球化学、地質年代学的解析を行った。本調査地域では、層状・葉状・上部塊状斑れい岩類、シート状岩脈群、噴出岩層から構成されるオフィオライト地殻中に、多様な深成岩類・火山岩岩脈が後期貫入している。後期貫入する深成岩類の岩相は、ダナイト～単斜輝岩からなる超塩基性集積岩類、かんらん石斑れい岩から含Fe-Ti 酸化物ガブロノーライトより構成される斜方輝石に富む斑レイ岩類（ガブロノーライト類）、閃緑岩～トロニエム岩からなる斜長花崗岩類に大別され、これらは早期に結晶化した斑れい岩地殻の中部に厚さ～4-5km、幅20km以上に及ぶ複合深成岩岩体を形成している。後期深成岩類の大規模な貫入は地殻の厚化をもたらし、全地殻層厚は～8-9kmに達する。また、後期貫入深成岩類に貫入する最後期の貫入岩として、WNW走向を持った数百のボニナイト質岩脈が４帯の平行岩脈群を形成している。後期の超塩基性集積岩類およびガブロノーライト類は、単斜輝石が斜長石よりも早期に晶出する結晶化順序を示し、単斜輝石のMg値(=100*Mg/[Mg/Fe])と斜長石のAn%(=100*Na/[Ca+Na])の組成共生関係において高いAn％を持つこと、単斜輝石の不適合元素濃度が早期の斑れい岩類に比べ枯渇していることなどから、後期火成活動の起源マグマが中央海嶺玄武岩（MORB）質マグマに比べて水に富み、より枯渇した組成であったと考えられる。また後期貫入超塩基性岩類の一部には、不適合元素濃度がより強度に枯渇したボニナイト的な輝石・クロムスピネルを伴うものが認められた。一方で、ガブロノーライト類に伴われる斜長花崗岩類は、海嶺起源の斜長花崗岩類に比べ不適合元素に枯渇しており島弧花崗岩類、およびオマーンオフィオライトにおける後期沈み込み帯起源タイプに区分される。これら後期の斜長花崗岩類はしばしば、玄武岩質マグマと斜長花崗岩質マグマの液相状態での混交関係を示す玄武岩質包有岩を伴う。それら包有岩はMORB に比べ不適合元素濃度に枯渇した組成を持ち、ガブロノーライト類から推定される親マグマ組成に調和的な組成傾向をもつことから、斜長花崗岩マグマに注入した玄武岩質マグマとガブロノーライト類の親マグマとは同起源であると推定される。したがって、後期貫入複合岩体を構成する超塩基性集積岩類、ガブロノーライト類、斜長花崗岩類は、枯渇した含水マグマからの一連の結晶分化プロセスで形成されたと結論づけられる。また、後期の斜長花崗岩類から抽出されたジルコンのU-Pb 年代測定値から94.0±0.7Ma前後の結晶化年代が見積もられた。これは、オフィオライトの衝上に伴って形成されたメタモルフィックソールの最高変成条件の年代値とされる94.5±0.2Maとほぼ同年代であり、後期貫入岩類の結晶化時には既に沈み込み帯の形成が開始されていたと解釈される。","subitem_description_type":"Abstract"},{"subitem_description":"最後期に貫入するボニナイト質岩脈群は、後期貫入コンプレックスの基底部付近の超塩基性岩類を根とし、斑晶の沈積・分別に由来する組成トレンドを持つことから、ボニナイト質の超塩基性集積岩類は斑晶鉱物の集積を伴うマグマ溜まりであったと考えられる。また、岩脈の組成傾向が未分化側でAlleyユニット中のボニナイト溶岩に類似すること、分化した高Mg 玄武岩・安山岩組成岩脈がAlley 溶岩類と調和的な組成を持つ事から、岩脈群がAlley 溶岩層の供給岩脈群であったと考えられる。初生的な岩脈は高Caボニナイトに分類され、後期貫入岩類の起源マグマよりもさらに不適合元素に枯渇し、M～HREEに対してTh およびLREE に富む特徴的な微量元素パターンを示す。これは、ボニナイト質岩脈群の起源となる枯渇マントルに、メタモルフィックソールから生じた堆積岩メルトが付加した痕跡として解釈される。本調査地域の下部地殻の火成史は次の通りに総括される。98-95Maと推定される海洋地殻層序の形成後、94.5Ma 以前に始まった沈み込み帯の形成に伴い、94Ma前後に含水枯渇マグマによる後期貫入深成岩類の形成が行われ、その後堆積岩起源メルトの付加を伴う部分溶融によって生成されたボニナイトメルトが岩脈群を形成した。後期貫入深成岩類の起源マグマV2 type-I or Lasail 溶岩層の火成活動に、ボニナイト質岩脈群はV2-type-II or Alley 溶岩層の火成活動にそれぞれ対比される。この後期貫入岩類形成は、伊豆マリアナ前弧域に代表される海洋性島弧の発生過程の海洋底内での沈み込み帯形成直後からボニナイト火成活動以前に相当する最初期の地殻発達プロセスとして解釈されることから、本調査地域は沈み込み帯の発生直後に～10km厚へと急激に厚化した海洋性島弧地殻断面の好例である。","subitem_description_type":"Abstract"},{"subitem_description":"Oman ophiolite is the largest ophiolite in the world, which is exposed as Oman Mountains on the northeast of Arabian Peninsula, Middle East. In order to discuss the evolution of late intrusive rocks in the crustal section, we have drawn new geological map, with about 25 km long and 12 km width, of the Rajmi area, which is located in the Fizh block in the northern part of Oman ophiolite. The crustal sequence of the Rajmi area contains large amount of various types of late intrusive plutonics and dikes into the early-crystalized ophiolitic crustal rocks that consists of layered, foliated and upper gabbros, sheeted dike complex and lava sequence, from bottom to top. The late intrusive plutonics are ultramafic cumulates from dunite to clinopyroxenite, gabbronorites (orthopyroxene-rich gabbros) and plagiogranites from diorite to trondhjemite. These lithologies formed late intrusive plutonic complex with ~ 4-5 km thick and over 30 km length into between the layered gabbro and foliated gabbro, contributing crustal thickening to ~8-9 km, which is apparently thicker than those of the other area. As the latest intrusion, WNW-trending boninitic dikes formed four bands of dike swarm, intruding into both of the early crustal rocks and the late intrusive plutonics. The late ultramafic cumulates and gabbronorites represent crystallization order of Ol > Cpx > Opx and Pl and the mineral chemical compositions with higher An% (=100*Na/[Ca+Na]) in plagioclase and lower concentrations in incompatible elements in clinopyroxene than those of the early gabbros. These indicate that the parental melts of the late plutonics are more hydrous and depleted than those of MORBs. Some ultramafic cumulates has highly depleted characteristics in mineral chemical compositions, which are corresponding to those of boninites. On the other hand, the plagiogranites associated with the late gabbronorites has depleted composition in incompatible elements, which are classified into volcanic arc granites and corresponds with subduction-related late plagiogranites in the ophiolite. These late plagiogranite often enclose basaltic enclave, which represent magma mingling relationship due to basaltic melt injection into plagiogranitic magma. The basaltic enclaves also have depleted compositions in the incompatible elements and its compositional trend is corresponding to those of the estimated parental melts from the gabbronorites, indicating that the basaltic enclaves originate in the parental melts of the late intrusive complex. It is concluded that a sequential fractional crystallization process from hydrous and depleted melts, which is corresponding to the Lasail or V2 type-I lavas, formed the late intrusive plutonics from ultramafic cumulate, gabbronorites to dioritic plagiogranites and enclaves. In addition, the crystallization age of 94.1±0.7 Ma was obtained from zircon U-Pb dating from the late plagiogranites, which is estimated as contemporaneous to 94.5±0.2 Ma at the peak metamorphic age of the metamorphic sole. This is considered that subduction beneath the ophiolite already started at the crystallization of the late intrusive plutonics.","subitem_description_type":"Abstract"},{"subitem_description":"As the latest intrusion, the boninitic dike swarms are rooted in the ultramafic cumulate of the late intrusive complex and they represent magmatic evolution through the lower crustal by fractional crystallization and phenocryst settling. The boninitic ultramafic cumulates are considered as plutonic phase of the boninitic dikes. The whole rock compositional trends of the less evolved dikes are cover those of boninite lavas within the upper lava unit (Alley unit), on the other hand, the evolved dike covers basaltic to dacitic lavas of the Alley unit. Thus the boninitic dike swarms were considered as feeders of the Alley lavas. The near primitive dikes, which are classified into high-Ca boninite, have highly depleted compositions with the enrichments in Th and LREE relative to M- to HREE. Trace element modeling demonstrates that these enrichments originate in involvements of sediment components from metamorphic sole into highly depleted source mantle. The magmatic history in the lower crust of the Rajmi area is summarized as follows; after the crystallization of the early crustal rocks from MORB beneath spreading ridge at 98-95 Ma, the crustal thickening by hydrated and depleted melts occurred around 94 Ma presumable due to subduction initiation before 94.5 Ma, and boninite magmatism subsequently occurred by partial melting of highly depleted mantle with influx of sediment melts and formed dike swarms. The magmatism formed late intrusive plutonics is comparable to the V2 type-I or Lasail unit, and the boninite dikes and cumulates are to the V2 type-II or Alley unit. The formation of the late intrusive complex, which occurred after subduction initiation and before boninite magmatism, is comparable to the nascent stage of crustal formation of oceanic island arc such as Izu-Mariana fore arc. The Rajmi area is good example for oceanic island arc crustal section, which rapidly developed to ~10 km thick immediately after subduction initiation event.","subitem_description_type":"Abstract"}]},"item_6_description_5":{"attribute_name":"内容記述","attribute_value_mlt":[{"subitem_description":"学位の種類: 博士（理学）. 報告番号: 甲第3773号. 学位記番号: 新大院博（理）甲第373号. 学位授与年月日: 平成25年3月25日","subitem_description_type":"Other"}]},"item_6_description_53":{"attribute_name":"学位記番号","attribute_value_mlt":[{"subitem_description":"新大院博（理）甲第373号","subitem_description_type":"Other"}]},"item_6_dissertation_number_52":{"attribute_name":"学位授与番号","attribute_value_mlt":[{"subitem_dissertationnumber":"13101A3773"}]},"item_6_full_name_3":{"attribute_name":"著者別名","attribute_value_mlt":[{"nameIdentifiers":[{"nameIdentifier":"50141","nameIdentifierScheme":"WEKO"}],"names":[{"name":"山崎, 秀策"}]}]},"item_6_publisher_7":{"attribute_name":"出版者","attribute_value_mlt":[{"subitem_publisher":"新潟大学"}]},"item_6_select_19":{"attribute_name":"著者版フラグ","attribute_value_mlt":[{"subitem_select_item":"ETD"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"Yamazaki, Shusaku"}],"nameIdentifiers":[{"nameIdentifier":"50140","nameIdentifierScheme":"WEKO"}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2019-08-05"}],"displaytype":"detail","filename":"D_S_R_K373.pdf","filesize":[{"value":"26.8 MB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"本文","url":"https://niigata-u.repo.nii.ac.jp/record/5355/files/D_S_R_K373.pdf"},"version_id":"a6736d89-33cf-4266-8127-62ba60937e6e"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"thesis","resourceuri":"http://purl.org/coar/resource_type/c_46ec"}]},"item_title":"Incipient island arc crust formation within oseanic crustal sequence : Geology, Geochemistry and Geochronology of late intrusive rocks in the Oman ophiolite","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Incipient island arc crust formation within oseanic crustal sequence : Geology, Geochemistry and Geochronology of late intrusive rocks in the Oman ophiolite"},{"subitem_title":"Incipient island arc crust formation within oseanic crustal sequence : Geology, Geochemistry and Geochronology of late intrusive rocks in the Oman ophiolite","subitem_title_language":"en"}]},"item_type_id":"6","owner":"1","path":["455","564"],"pubdate":{"attribute_name":"公開日","attribute_value":"2013-11-20"},"publish_date":"2013-11-20","publish_status":"0","recid":"5355","relation_version_is_last":true,"title":["Incipient island arc crust formation within oseanic crustal sequence : Geology, Geochemistry and Geochronology of late intrusive rocks in the Oman ophiolite"],"weko_creator_id":"1","weko_shared_id":2},"updated":"2022-12-15T03:38:21.176023+00:00"}