Proterozoic Mobile Belts of Gondwana -Comparative study of Precambrian geology between India and Antarctica-

在本研究项目（两年，1993-1994年）下，资助了25名日本科学家和13名印度科学家的实地活动和有关开支，共计813人日（资金总额为21，000，000日元）。实地调查覆盖了印度半岛南部至东南部的前寒武纪地形，并收集了地质数据，包括重量超过3,000公斤的岩石样本。我们工作的初步结果出现在约26篇论文（全部为英文）和32个口头报告，主要是在国际研讨会上。这些工作的要点如下。(1)对印度、南极洲和斯里兰卡的近期地质资料进行了认真总结和对比。晚元古代冈瓦纳大陆与中生代冈瓦纳大陆基本相似。(2)新近报道了Palghat-Cauvery构造线以南麻粒岩的几种矿物等时线年龄，约为500 Ma。因此，印度半岛的前寒武纪被划分为构造线以北的侏罗纪地体和以南的以约500 Ma事件为主的元古代地体。(3)首次报道了典型的马德拉斯麻粒岩的Sm-Nd矿物等时线年龄为3.0Ga。首次从戈达瓦里河谷以南的Karimnagar麻粒岩带获得了几个岩石Pb-Pb等时线年龄，表明麻粒岩形成于早于约2.6Ga的中生代。(4)在印度南部、斯里兰卡和南极洲发现了泛非期麻粒岩的形成和变质事件。对麻粒岩事件提出了与地幔脱气有关的CO_2喷流的伸展构造模式。(5)指出了东南极周围约1.1Ga带的重要性，并提出了环东南极移动的带的概念。该带被认为主要与东冈瓦纳大陆的诞生有关。

Under the present research project (2 years, 1993-1994), 25 scientists from Japan and 13 scientists in India, totalizing 813 man-days, were funded for the field activities and related expenditures (total fund was 21,000,000 yen). The field survey covered Precambrian terrains in southern to southeastern Peninsular India and collected geologic data including rock samples of more than 3,000 kg in weight. Preliminary results of our work appeared in about 26 papers (all in English) and 32 oral presentations mostly in international symposiums. Important points of these works are given below.(1) Recent geologic informations of India, Antarctica and Sri Lanka were critically summarized and correlated. The Gondwana during late Proterozoic is found to be principally similar to that of Mesozoic.(2) Several mineral isochron ages of ca 500 Ma have been newly reported for granulites south of the Palghat-Cauvery tectonic line. Thus, the Precambrian of Peninsular India is divided into the Archaean terrain north of the tectonic line and the Proterozic terrain with dominant ca 500 Ma events to the south.(3) A Sm-Nd mineral isochron age of 3.0 Ga was first reported from the classic Madras granulite. Several Pb-Pb rock isochron ages were first obtained from rocks of the Karimnagar Granulite Belt south of Godavari Valley, and indicated that the granulites were formed during Archaean older than ca 2.6 Ga.(4) The granulite formation and correlatable events during the Pan African stage were identified in South India, Sri Lanka and Antarctica. An extensional tectonic model associated with the CO_2 flushing related with the mantle degassing was presented for the granulite events in the above areas.(5) Importance of the ca 1.1 Ga belt surrounding East Antarctica was pointed out and the term Circum East Antarctic Mobile Belt has been proposed. The belt is suggested to be principally related to the birth of the East Gondwana.