Petrochemistry of Kimberlites, Lamproites and Diamonds in India

Haggertyoung-0106187钻石首次发现于大约400万年前的印度。许多世界上最著名的钻石（大莫卧儿，奥尔洛夫，沙阿，达里亚-i-努尔，摄政王，尼扎姆），以及许多臭名昭著的石头（如希望，光-i-努尔），都是从南部安得拉邦克里希纳河沿岸的冲积矿床中发现的。这些钻石和许多其他非凡钻石的主要来源，就大小和净度而言，尚未找到。与全世界钻石矿床的地质背景一样，印度的钻石也位于火山和移动的带上。两个著名的钻石区是Majhgawan（自公元13世纪以来就被称为）和Wajrakarur，前者是位于Bundelkand邦（中央邦）的一个正在开采的钻石矿，后者位于Andra Pradesh邦的Dharwar邦。这两个地区的侵入体的年龄都是元古代的，大约在1.1 Ga的年龄与南非的Premier金伯利岩（库利南的来源，有史以来报道的最大的金刚石钻石）和澳大利亚的阿盖尔钾镁煌斑岩（世界上最大的生产者，超过40百万克拉/年）相似。这两个地点沿着中非和巴西的元古代冲积层，位于重建的Rodinia超大陆的主要线性构造沿着。这被解释为与羽流有关。在过去的十年中，印度发现了50多个新的侵入体，这些古老的侵入体是研究地幔状态及其与地壳演化关系（TTG）的重要新实验室。印度的金刚石寄主岩既不是经典的金伯利岩，也不是传统的钾镁煌斑岩，并被不同地描述为具有金伯利岩（矿物学）和钾镁煌斑岩（地球化学）的亲和力。这是地幔岩石化学研究的一个新的重大挑战。许多侵入体具有丰富的地幔捕虏体，有的是强烈的榴辉岩，有的是以橄榄岩为主，这两种侵入体都将为亚俯冲岩石圈龙骨的成分和热状态提供新的认识。印度的地幔图绘制得很好，地幔数据库将提供一套独立的约束条件来模拟深部地幔。将对32个侵入体的地幔样品进行显微镜研究，并使用电子显微束和X射线荧光技术进行分析，以分别获得矿物和大块岩石的成分。金刚石形态将通过立体和扫描电子显微镜，并通过拉曼和红外光谱检查。这些数据将提供印度元古代地幔侵入岩的第一次全面研究。重要的新见解的预测和重要的新的解释预计，不仅在印度，但在更广泛的背景下，钻石矿床在Rodinia。

HaggertyEAR-0106187Diamonds were first discovered in India some four millinnia ago. Many of the world's most famous diamonds (Great Mogul, Orloff, Shah, Darya-i-Noor, Regent, Nizam), as well as many infamous stones (e.g. Hope, Koh-i-Noor), were recovered from alluvial deposits on the banks of the Krishna River in the southern state of Andra Pradesh. The primary sources of these and many other extraordinary diamonds, in terms of size and clarity, have not been located. In common with the geological setting of diamond deposits worldwide, diamonds in India are also on cratons and in mobile belts. The two prominent diamond districts are Majhgawan (known since the 13th C), which is an operating mine in the Bundelkand Craton (Madhya Pradesh), and Wajrakarur in the Dharwar Craton of Andra Pradesh. The ages of intrusions in both districts are Proterozoic, and at about 1.1 Ga are similar in age to the Premier kimberlite (source of the Cullinan, the largest diamond diamond ever reported) in South Africa, and the Argyle lamproite (the world's largest producer, over 40 M cts/yr) in Australia. These two sites, along with Proterozoic alluvial deposits in central Africa and Brazil, lie along major lineaments in the reconstructed supercontinent of Rodinia. This is interpreted to be plume related. With over 50 new intrusives discovered in India over the past decade, these ancient cratons are an important new laboratory to study the state of the mantle, and its evolutionary relation the crust (TTG). The diamond host rocks in India are neither classical kimberlites nor conventional lamproites and are variously described as having both kimberlitic (mineralogically), and lamproitic (geochemically) affinities. This is a significant new challenge in mantle petrochemistry. Many intrusions have abundant mantle xenoliths, some are intensely eclogitic, and others are dominantly peridotitic, and both will provide new insights to compositions and thermal states of subcratonic lithospheric keels. India is well mapped geophysically and the mantle data base will provide an independent set of constraints to model the deep mantle. Mantle samples from 32 intrusions will be studied microscopically and analysed using electron microbeam and x-ray fluoresence techniques to obtain mineral and bulk rock compositions, respectively. Diamond morphologies will be examined by stereo- and scanning electron microscopy, and by Raman and infrared spectroscopy. These data will provide the first comprehensive study of Proterozoic mantle intrusives in India. Significant new insights are predicted and important new interpretations are anticipated, not only in India but in the broader context of diamond deposits in Rodinia.