An integrated petrographic, fluid inclusion, noble gas, and stable isotope study was performed for the Late Oligocene, spatially associated Sukulu and Tororo carbonatite complexes in SE Uganda in order to understand their genesis and provide additional constraints on the evolution of the East African Rift System (EARS). Both carbonatite complexes comprise mainly ring-shaped calcio‑carbonatites with accessory primary magmatic phases, including olivine, phlogopite, aegirine and pyrochlore. Absent or low Na deficiency on the A-site and high F contents (0.4–1.2 apfu) reveal the magmatic origin of pyrochlore. In contrast, the corroded rims of olivine, Sr-enrichments of the rims of apatite, as well as the occurrence of Sr- and Mg-rich lamellae in calcite, coupled with the presence of barite, REE-witherite, siderite, pyrite, bastnäsite and galena as secondary phases imply a hydrothermal overprint of the primary magmatic mineral assemblage.

Fluid inclusions found in the cores of clustered apatite crystals are primary, two-phase H₂O + NaCl aqueous inclusions in Sukulu-, and two-, or multi-phase H₂O + NaCl ± NaHCO₃ ± other solid inclusions in Tororo Complex. In the gas phase of some inclusions small amounts of CO₂ or CH₄ have been detected by micro-Raman analysis. The estimated trapping temperature of 330–425 °C and pressure of 465–1330 bars using the accepted denudation rates calculated for the EARS as independent barometers, reveal subsolidus crystallization conditions for the intercrystalline clustered apatite aggregates. Stable C-O isotope compositions of both carbonatite complexes suggest ultimately a mantle origin for the carbonate phase.

Helium, neon and argon isotope compositions, liberated by crushing of bulk rock, apatite and calcite samples, show a systematic variation between the analyzed phases. Relatively low ³He/⁴He ratios of apatite and pyroxene separates (<5.3 R_a) are accounted for by radiogenic production of ⁴He in these minerals, whereas the air-corrected values in calcite reach as high as 9.6 R_a, characteristic for plume sources. Whole-rock Ne isotope ratios provide evidence for a depleted MORB mantle (DMM) trend. Combined (²¹Ne/²²Ne)_EX (air-corrected ²¹Ne/²²Ne ratio extrapolated to Ne-B composition Holland and Ballentine, 2006; Trieloff et al., 2000) versus ⁴He/³He are indicative of mixing of a plume-like and a DMM-like component in the source region of the parental carbonatite magmas, which is in contrast to some recent interpretations of recent/sub-recent magmas in the EARS. Based on new noble gas data from this study we argue that in the early phase of the magmatic activity of the EARS, a low-viscosity carbonatite magma may have intruded into the shallow crust rapidly, without any significant contamination by the sub-continental lithospheric mantle.

Combined fluid inclusion data and noble gas results collectively imply that the carbonatites worldwide are carbothermal (hydrothermal) rather than purely magmatic products and that they crystallized at sub-solidus temperatures from dominantly magma-derived fluids.

对乌干达东南部晚渐新世，空间相关的Sukulu和Tororo碳酸盐复合体进行了岩石学，流体包裹体，稀有气体和稳定同位素的综合研究，以了解其成因并为东非裂谷系统的发展提供其他限制（耳朵）。两种碳酸盐复合物均主要为环形钙碳质碳酸盐，并伴有初级岩浆相，包括橄榄石，金云母，a色氨酸和烧绿石。A位缺乏或低Na缺乏和高F含量（0.4–1.2 apfu））揭示烧绿石的岩浆成因。相比之下，橄榄石的轮缘腐蚀，磷灰石轮缘的Sr富集以及方解石中富Sr和Mg的片晶的出现，以及重晶石，REE堇青石，菱铁矿，黄铁矿，黄铁矿的存在和方铅矿作为次生相暗示着主要岩浆矿物组合的热液叠印。

在簇状磷灰石晶体芯中发现的流体夹杂物是Sukulu-中的初级，两相H ₂ O + NaCl含水夹杂物，以及 Tororo络合物中的两相或多相H ₂ O + NaCl±NaHCO ₃ ±其他固体夹杂物。在某些夹杂物的气相中，少量的CO ₂或CH₄已通过微拉曼分析检测到。使用为EARS计算的公认剥蚀率作为独立的晴雨表，估计的捕集温度为330–425°C，压力为465–1330 bar，揭示了晶间簇状磷灰石聚集体的亚固相结晶条件。两种碳酸盐配合物的稳定的CO同位素组成最终表明碳酸盐相的地幔成因。

通过破碎大块岩石，磷灰石和方解石样品释放出的氦，氖和氩同位素组成显示了分析相之间的系统变化。磷灰石和辉石分离物的³ He / ⁴ He比率相对较低（<5.3 R _a）是由这些矿物的放射成因产生⁴ He引起的，而方解石中的空气校正值高达9.6 R _a，这是矿物的特征。羽流来源。全岩的Ne同位素比率为MORB地幔（DMM）枯竭趋势提供了证据。组合（²¹ Ne / ²² Ne）_EX（空气校正的²¹ Ne / ²²Ne比率推断为Ne-B组成荷兰和巴伦丁，2006年；Trieloff et al。，2000）与⁴ He / ³ He的关系表明在母岩质碳酸盐岩浆源区混合了羽状成分和DMM成分，这与最近对近/次岩浆的一些解释相反。耳中最近的岩浆。根据这项研究的新的惰性气体数据，我们认为在EARS岩浆活动的早期，低粘度的碳酸盐岩浆可能已迅速侵入浅层地壳，而没有受到陆下岩石圈地幔的任何重大污染。 。

流体包裹体数据和稀有气体的综合结果共同表明，全世界的碳酸盐岩是碳热（热液）而不是纯岩浆产品，并且它们在低于固相线的温度下从主要来自岩浆的流体中结晶。