Terminal Gondwana assembly occurred along the Cambrian Kuunga suture with the collision of the late Neoproterozoic Greater India–Enderbia plate and the combined North Australian–Mawson-Crohn cratonic block, supported by paleomagnetic latitudinal positions from India between 750 and 500 Ma. As the scale of the collision would have resulted in far-field intraplate orogenesis, one likely locale to be affected is the 990–940 Ma Eastern Ghats Belt (EGB) in southeastern India, exposing reworked granulitic middle to lower crust. The EGB (conjugate to the Rayner Complex, East Antarctica) is a collage of Archean and Paleoproterozoic crustal provinces separated by high-grade ductile shear zones. From the ∼933 Ma polydeformed Bolangir anorthosite in a Paleoproterozoic EGB province, an attempt was made to constrain the time of the amphibolite facies reworking to test possible Cambrian synchronicity of exhumation of middle to lower crust with the 530–490 Ma Kuunga orogeny. Anorthosites have Paleoproterozoic depleted-mantle model ages (∼1.9 Ga, with ε Nd ( 930 Ma ) = −3.6 and −4.9) implying significant crustal assimilation. Combined anorthosite-garnet isochrons of samples PN 581e and PN 604 yielded an age of 495 ± 9 Ma, with Ndi of 0.51150 ± 0.00003 and MSWD of 2.9 ( n = 4 ). The isochron age from ferrodiorite PN 581e and PN 589 garnet fraction b and its leachate was 481 ± 12 Ma, with Ndi of 0.51155 ± 0.00005 and MSWD of 0.02 ( n = 3 ), whereas this age from multigrain garnet fraction c and its leachate was 475 ± 16 Ma, with Ndi of 0.51180 ± 0.00006 . The ∼500 Ma garnet ages from the anorthosite and ferrodiorite are interpreted as a regional upper amphibolite facies tectonothermal event. Localization, strain partitioning, and tectonic exhumation of middle to lower crust during Cambrian intraplate orogeny were due to (1) interaction of the in-plane stress field with the heterogeneous terranes comprising the Tonian-age EGB–Rayner Complex orogeny, (2) juxtaposition with a rheologically contrasted cratonic domain, and (3) thermal weakening due to the high-crustal-heat-flow regime.

中文翻译：

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来自印度东高止山脉多变形 Bolangir 斜长岩复合体的寒武纪石榴石 Sm-Nd 同位素年龄：冈瓦纳组装期间板内造山运动与 Kuunga 造山运动同期的意义

随着晚新元古代大印度-恩德比亚板块和北澳大利亚-莫森-克罗恩克拉通地块的碰撞，冈瓦纳末期组装发生在寒武纪库恩加缝合带，并得到印度 750 至 500 Ma 之间的古地磁纬度位置的支持。由于碰撞的规模会导致远场板内造山作用，一个可能受到影响的地点是印度东南部 990-940 Ma 东高止山脉带 (EGB)，暴露了重新加工的麻粒质中下地壳。EGB（与东南极洲的 Rayner Complex 共轭）是太古代和古元古代地壳区的拼贴，被高等级韧性剪切带分隔开。来自古元古代 EGB 省的 ∼933 Ma 多变形 Bolangir 斜长岩，试图限制角闪岩相改造的时间，以测试可能的寒武纪中下地壳剥蚀与 530-490 Ma Kuunga 造山运动的同步性。斜长岩具有古元古代耗尽地幔模型年龄（~1.9 Ga，ε Nd（930 Ma）= -3.6 和 -4.9），这意味着显着的地壳同化作用。PN 581e 和 PN 604 样品的斜长岩-石榴石等时线组合得出的年龄为 495 ± 9 Ma，Ndi 为 0.51150 ± 0.00003，MSWD 为 2.9 (n = 4)。铁闪长岩 PN 581e 和 PN 589 石榴石级分 b 及其浸出液的等时线年龄为 481 ± 12 Ma，Ndi 为 0.51155 ± 0.00005，MSWD 为 0.02 ( n = 3 )，而该多粒石榴石级分 c 及其浸出液的等时线年龄为475 ± 16 Ma，Ndi 为 0.51180 ± 0.00006。来自斜长岩和铁闪长岩的约 500 Ma 石榴石年龄被解释为区域上角闪岩相构造热事件。寒武纪板内造山运动期间中下地壳的定位、应变分配和构造剥露是由于（1）面内应力场与包含托尼阶EGB-Rayner复合造山运动的非均质地体的相互作用，（2）并置具有流变学对比的克拉通域，以及 (3) 由于高地壳热流状态而导致的热减弱。