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

在本研究项目（2年，1993-1994年）下，来自日本的25名科学家和印度的13名科学家，共计813个工作日，用于实地活动和相关支出（资金总额为2 100万日元）。实地调查覆盖了印度半岛南部到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。我们工作的初步结果发表在大约26篇论文（全部是英文）和32个口头报告中，主要是在国际研讨会上。这些作品的要点如下。(1)对印度、南极洲和斯里兰卡最近的地质资料进行了批判性总结和对比。发现晚元古代的冈瓦纳与中生代的冈瓦纳基本相似。(2)在Palghat-Cauvery构造线以南的麻粒岩中，新报道了几个约500 Ma的矿物等时线年龄。因此，将印度半岛前寒武纪划分为构造线以北的太古宙地形和以500 Ma事件为主的元古代地形。(3)在经典马德拉斯麻粒岩中首次发现了3.0 Ga的Sm-Nd矿物等时线年龄。首次从戈达瓦里谷南Karimnagar麻粒岩带的岩石中获得了Pb-Pb等时线年龄，表明麻粒岩形成于约2.6 Ga以上的太古代。(4)确定了南印度、斯里兰卡和南极洲泛非期麻粒岩的形成和相关事件。对该区麻粒岩事件提出了一个与地幔脱气相关的CO_2冲洗相关的伸展构造模型。(5)指出了围绕东南极洲的约1.1 Ga带的重要性，提出了“环东南极洲活动带”的概念。该带被认为主要与东冈瓦纳的诞生有关。

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.