Rubidium-Strontium Whole-Rock Ages of Kataragama and Pottuvil Charnockites and East Vijayan Gneiss: Indication of a 2 Ga Metamorphism in the Highlands of Southeast Sri Lanka: A Discussion
Rubidium-Strontium Whole-Rock Ages of Kataragama and Pottuvil Charnockites and East Vijayan Gneiss: Indication of a 2 Ga Metamorphism in the Highlands of Southeast Sri Lanka: A Discussion
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Kataragama 和 Pottuvil Charnockites 以及 East Vijayan 片麻岩的铷-锶全岩年龄：斯里兰卡东南部高地 2 Ga 变质作用的迹象：讨论
DOI：
10.1086/629540
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
V. Mathavan
中科院分区：
文献类型：
--
作者：
V. Mathavan
de Maesschalck 等人提出的新的 Rb-Sr 全岩同位素数据。 (1990)关于斯里兰卡东南部的霞岩和片麻岩的研究是对斯里兰卡前寒武纪地质年代演化持续争论的及时贡献。 1987-1990 年期间在斯里兰卡岩石上产生的大量同位素数据造成了一个令人困惑的情况，其中 (a) 高地群麻粒岩相变质作用的年龄被确定为 1100 Ma（Kroner 等人，1987）、650-720 Ma（Kroner 1990）、600 Ma（Liew 等人，1990）； Holzl 和 KOhler 1990）、500-400 Ma（Kagami 等人 1990），以及早先获得的 2000-2500 Ma 日期（Crawford 和 Oliver 1969；Wickremasinghe 1969；以及 cf. Holland 1985）； (b) 麻粒岩的地壳停留时间经计算长至 2 Ga（Kroner 等人，1987 年；Liew 等人，1990 年），短至 0.3 Ga（Holland，1985 年）； (c) 钙镁铁矿的发育停滞，其明显晚于主要的区域变质作用，已确定为 746 ± 25 Ma（Baur 等人，1987 年）。 de Maesschalck 等人的工作。证实了 Crawford 和 Oliver (1969) 和 Wickremasinghe (1969) 为斯里兰卡高地群麻粒岩相变质作用早期获得的 Rb-Sr 全岩等时线日期。作者通过从采石场或露头仔细收集与岩石成因相关的样本来回应早期的批评，即“克劳福德和奥利弗的样本无关，并且是在一个偏远地区收集的”。然而，这
The new Rb-Sr whole-rock isotopic data presented by de Maesschalck et al. (1990) on the charnockites and gneisses of southeast Sri Lanka is a timely contribution to the continuing debate on the geochronological evolution of the Precambrian of Sri Lanka. The burst of isotopic data produced on the Sri Lankan rocks during the period 1987-1990 has created a confusing scenario where (a) the age of granulite facies metamorphism of the Highland Group has been dated as 1100 Ma (Kroner et al. 1987), 650-720 Ma (Kroner 1990), 600 Ma (Liew et al. 1990; Holzl and KOhler 1990), and 500-400 Ma (Kagami et al. 1990), in addition to the earlier obtained date of 2000-2500 Ma (Crawford and Oliver 1969; Wickremasinghe 1969; and cf. Holland 1985); (b) the crustal residence time of the granulites has been calculated to be as long as 2 Ga (Kroner et al. 1987; Liew et al. 1990) and as short as 0.3 Ga (Holland 1985); (c) the arrested development of charnockite, which clearly postdates the main regional metamorphism, has been dated as 746 ± 25 Ma (Baur et al. 1987). The work of de Maesschalck et al. confirms the earlier Rb-Sr whole-rock isochron date obtained by Crawford and Oliver (1969) and Wickremasinghe (1969) for the granulite facies metamorphism in the Highland Group of Sri Lanka. The authors have responded to the earlier criticism that "Crawford and Oliver's samples were unrelated and collected over a regional area," by carefully collecting petrogenetically linked samples from a quarry or an outcrop. However, this