Pyrochlore-group minerals are common accessory rare-metal bearing minerals in the calcite and ankerite carbonatites of the Amba Dongar complex (India). Pyrochlore from the Amba Dongar carbonatites differs from that in other Indian complexes in Ta, Zr, Ti, rare earth element (REE) and Pb contents, but is similar with respect to Ca, Ba and Sr abundances. The evolution of pyrochlore composition was studied to understand the alteration processes and the formation of late-stage pyrochlores enriched in REE and Pb. The early magmatic pyrochlore are calcio- and niobium-dominant types and were replaced by secondary cation-deficient varieties as a consequence of the action of hydrothermal fluids and supergene weathering. These processes produce changes mainly at the A site, rarely at the B site, and the original F is replaced by OH– groups. Calcium and Na can be extracted from the structure at the alteration stage and charge balance is achieved by the introduction of REE, Th, U, Ba or Sr. At the latest supergene stages, marginal and fractured zones of pyrochlore grains are altered to Pb-rich, Si-rich and cation-deficient hydrated varieties. The magmatic pyrochlore was crystallised in a highly alkaline environment at a high activity of Ca and at temperatures near 600°C, the alteration of pyrochlore began in a hydrothermal environment at temperatures below 350°C. The major compositional changes that are associated with the alteration are summarised by the following reactions: Ca2+ + Nb5+→ REE3+ + Ti4+; Nb5+ + Fe3+ → Ti4+ + Zr4+; and 2Nb5+ + Ca2+ → Ti4+ + Si4+ + U4+.

烧绿石族矿物是Amba Dongar 复合体（印度）的方解石和铁长石碳酸岩中常见的含稀有金属的副矿物。来自 Amba Dongar 碳酸盐岩的烧绿石在 Ta、Zr、Ti、稀土元素 (REE) 和 Pb 含量方面不同于其他印度复合物中的烧绿石，但在 Ca、Ba 和 Sr 丰度方面相似。研究烧绿石成分的演变，以了解富含 REE 和 Pb 的后期烧绿石的蚀变过程和形成。早期的岩浆烧绿石以钙和铌为主导类型，由于热液作用和表生风化作用而被次生缺乏阳离子的品种所取代。这些过程主要在A点产生变化，很少在B点产生变化位点，原来的 F 被替换为 OH -基团。在蚀变阶段可以从结构中提取钙和钠，通过引入 REE、Th、U、Ba 或 Sr 来实现电荷平衡。在最新的表生阶段，烧绿石颗粒的边缘和断裂带被蚀变为 Pb-富、富硅和缺乏阳离子的水合品种。岩浆烧绿石在高Ca活度和600℃附近的高碱性环境中结晶，烧绿石的蚀变开始于350℃以下的热液环境。与变化相关的主要成分变化总结为以下反应：Ca 2+ + Nb 5+ → REE 3+ + Ti4+ ; Nb 5+ + Fe 3+ → Ti 4+ + Zr 4+；和2Nb 5+ + Ca 2+ → Ti 4+ + Si 4+ + U 4+。