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，日本25名科学家和印度13名科学家共813个人日获得了实地活动和有关支出的经费(资金总额为2100万日元)。实地考察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3000公斤的岩石样本。我们工作的初步成果发表在大约26篇论文(均为英文)和32篇口头报告中，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最新地质信息进行了批判性的总结和对比。晚元古代冈瓦那与中生代基本相似。(2)Palghat-Cauvery构造线以南麻粒岩的矿物等时线年龄为500 Ma左右。因此，印度半岛前寒武纪被划分为构造线以北的太古代地体和以500 Ma左右事件为主的元古宙地体。(3)首次从经典的马德拉斯麻粒岩中获得了3.0Ga的Sm-Nd矿物等时线年龄。首次从哥达瓦里谷南Karimnagar麻粒岩带岩石中获得了几个等时线年龄，表明麻粒岩形成于太古代，年龄大于2.6Ga。(4)在南印度、斯里兰卡和南极洲发现了泛非洲阶段麻粒岩的形成和相关事件。对上述地区麻粒岩事件提出了与地幔脱气相关的CO_2冲刷相关的伸展构造模式。(5)指出了东南极周缘Ca1.1Ga带的重要性，并提出了东南极活动带的概念。该带被认为主要与东冈瓦那的诞生有关。

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.