Rb-Sr, Sm-Nd ages of the Phalaborwa Carbonatite Complex, South Africa

We analyzed Rb-Sr and Sm-Nd isotopic compositions of whole-rock and minerals from syenite, biotite gneiss xenolith, dolerite dyke, phoscorite, and carbonatite from the Phalaborwa Carbonatite Complex located in northeastern Transvaal, South Africa. Syenite does not give significant Rb-Sr and Sm-Nd whole-rock and mineral isochron ages. Dolerite gives an Rb-Sr whole-rock and mineral isochron age of 2062±74Ma. This age overlaps with the timing of the magmatism of the Phalaborwa Carbonatite Complex. Biotite gneiss and phoscorite do not also give significant Rb-Sr and Sm-Nd isochrons. The Rb-Sr whole-rock and mineral isochron of phoscorite, however, gives an age of 2013±93Ma. The age is clearly the cooling age of this complex. Carbonatites are divided into two groups, having low and high initial Sr isotopic ratios. This coordinates with the result of S.C. Eriksson (Carbonatites, ed. by K. Bell, 1989). In addition, these groups indicate different initial Nd isotopic ratios. These suggest that carbonatite and related rocks were formed by mixing of two source magmas having different Sr and Nd isotopic compositions

Geochemistry of syenite of the Phalaborwa Carbonatite Complex, South Africa

We surveyed the Spitskop syenite pipe,one of the satellite bodies of the Phalaborwa Carbonatite Complex located in northeastern Transvaal,South Africa. This pipe is composed of the inner cumulus syenite and outer ring syenite.The brecciation zone between these syenites includes many blocks of syenite,pyroxenite, melanocratic rock,biotite gneiss and granitic rocks.Dolerite dykes intruded into the plug and brecciation zone.Fine-and coarse-grained syenites,melanocratic rock, alkali-feldspar granite and dolerite were collected from the brecciation zone of this pipe.The whole-rock and mineral chemistry suggests that syenites and melanocratic rocks of the brecciation zone were derived from the inner cumulus syenite magma. These rocks do not indicate any clear isochron.It may be a result of mixing of various rocks at the brecciation stage

Resetting and closing codition of Rb-Sr whole-rock isochron system: some samples of metamorphic and granitic rocks from the Gondwana super-continent and Japan Arc

The closure temperature of the Rb-Sr whole-rock system for felsic rocks has been generally considered to be ca. 700゜C, but it falls to ca. 400゜C, as a result of efficient action of fluids,especially H_2O. Thus,the Rb-Sr whole-rock ages obtained by rocks collected from a single outcropto specimen-size are not always coincident with those of emplacement of granitic magma or partial melting under high grade metamorphism.Although the Rb-Sr whole-rock isochron ages of metamorphic rocks collected from a wide area have been sometimes interpreted as those of metamorphism,careful consideration for these ages is needed

Mineral paragenesis and its implications in the högbomite-bearing skarn, Sør Rondane Mountains, East Antarctica

第2回極域科学シンポジウム/第31回極域地学シンポジウム 11月17日（木） 国立極地研究所　2階大会議

ヒガシ ドロンイングモードランド, セール・ロンダーネ サンチ チガク チョウサタイ ホウコク 2008-2009 (JARE-50)

第50次日本南極地域観測隊(JARE-50)夏隊・セール・ロンダーネ山地地学調査隊は,山地西部地域の地質調査を実施した(国立極地研究所一般研究プロジェクト,P-5-1:代表・本吉洋一).調査地へは,ドロンイングモードランド航空ネットワークを利用して空路ケープタウンから山地に入った.メンバーの構成は,地質調査担当5名とフィールドアシスタント1名である.調査地では三つのキャンプ(ベースキャンプ,前進キャンプ1および前進キャンプ2)を設営し,75日間すべてテントで生活した.本報告では,セール・ロンダーネ山地地学調査隊の設営,西部の気象条件および野外調査結果を含め,調査計画から実施に至る過程について記述する.The Sør Rondane Mountains field party, part of the summer party of the 50th Japanese Antarctic Research Expedition (JARE-50), consisted of five geologists and one field assistant, and conducted geological fieldwork in the western Sr Rondane Mountains, Eastern Dronning Maud Land, as part of a research project of the National Institute of Polar Research (#P-5-1). The field party accessed the mountains using the Dronning Maud Land Air Network (DROMLAN) from Cape Town to a runway close to the Belgian base, via the Novolazarevskaya runway. The field party made three campsites (Base Camp, Camp 1, and Camp 3) and stayed on the snowfield for 75 days. Here, we report the detailed operation plans and present a summary of the fieldwork, including information on logistics and weather reports for the western Sør Rondane Mountains

Whole-rock chemical compositions of granitic dykes in western part of the Sør Rondane Mountains, East Antarctica

第6回極域科学シンポジウム[OG] 地圏11月16日（月）　国立極地研究所１階交流アトリウ

Zirconolite from högbomite-bearing metamorphic rocks from the Koyubi-Ridge, Sør Rondane Mountains, East Antarctica

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月30日（金） 国立極地研究所 ３階ラウン

ナンキョク ヤガイ チョウサ ニ オケル タイヨウコウ ハツデン システム ノ カツヨウ ダイ50ジ ニホン ナンキョク チイキ カンソクタイ セール・ロンダーネサンチ チガク チョウサタイ ノ レイ

第50次日本南極地域観測隊(第50次隊)夏隊のセール・ロンダーネ山地地学調査隊は67日間におよぶ野外調査を行い,その間に必要な電力を太陽光発電で賄った.今回使用した太陽光発電システム(出力電圧約12 V)の1日あたりの発電量は6724 Ahであった.そして,この調査によって以下の3つの重要なことが明らかとなった.1)南極での野外調査生活に必要な電力は太陽光発電システムにより得ることが可能である.2)最大出力電流2.3 Aの太陽パネルは1日あたり910 Ahを発電する.3)夏季の南極は白夜のために日照が途絶える事はないが,当山地では0000 LTから0500 LT (昭和基地時刻) の間に太陽光発電ができない.The field party in the Sør Rondane Mountains, a part of the summer party of the 50th Japanese Antarctic Research Expedition (JARE-50), performed as outdoor survey using a solar-electric system for field camping over a period of 67 days. The total amount of power generation (output: ca 12V) varied from 67 to 24 Ah/day. We obtained three important conclusions: 1) Electric power is sufficiently supplied from the solar-electric system in the field camp. 2) The solar panel (maximum output 2.3 A) used by JARE-50 generates 9-10Ah/day. 3) The solar panel did not produce electric power during the midnight sun (0000-0500 LT; the time for Showa Station area) in the Antarctic summer season

Late Proterozoic juvenile arc metatonalite and adakitic granitoids in the Sør Rondane Mountains, East Antarctica

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月30日（金） 国立極地研究所 ３階ラウン