The ancestral South Sandwich arc (ASSA) records evidence of Oligocene – Miocene intra-oceanic island arc volcanism in the central Scotia Sea and potentially formed an important topographic barrier to deep ocean currents during the early development of the Antarctic Circumpolar Current. New geochemistry and geochronology of dredged basaltic samples from multiple sites across Discovery Bank, in the southern part of the ASSA, provide key information about this poorly understood volcanic arc in the Scotia Sea. Two new ⁴⁰Ar/³⁹Ar ages confirm volcanism was active in the Discovery Bank segment from 14 to 10 Ma, overlapping with the initial phase of spreading along the East Scotia Ridge. These ages are younger than previously determined for the ASSA and the island arc chain would have influenced deep ocean pathways in the southern Scotia Sea during the mid-Miocene. Geochemical analysis indicates that magmatism was derived from a depleted asthenospheric source, modified by subduction, akin to the present day South Sandwich island arc. Evidence from across Discovery Bank suggests that arc volcanism developed on pre-existing basaltic crust potentially related to Weddell Sea subduction, although the submerged bank is dominated by Miocene arc volcanic rocks. Evidence for an intra-oceanic island arc setting is also provided by the identification and imaging of a linear chain of rear-arc seamounts, characteristic of several volcanic centres in the present day South sandwich island arc. Mafic volcanic rocks, including ultramafic lithologies, from the neighbouring Bruce Bank topographic high have also been investigated and are demonstrated to have been generated in a different tectonic setting to the volcanic rocks of Discovery Bank. They are interpreted to be associated with the opening of Scan Basin during the Late Eocene, or potentially distal evidence of the gabbroic Pacific Margin Anomaly.

祖先的南桑威奇弧（ASSA）记录了斯科舍海中部渐新世-中新世洋内岛弧火山活动的证据，并可能在南极绕极流的早期发展过程中形成了一个重要的深洋流地形障碍。来自 ASSA 南部发现银行多个地点的疏浚玄武岩样品的新地球化学和地质年代学提供了关于这个在斯科舍海知之甚少的火山弧的关键信息。两个新的⁴⁰ Ar/ ³⁹Ar 年龄证实了从 14 到 10 Ma，Discovery Bank 段的火山活动活跃，与沿东斯科舍海脊蔓延的初始阶段重叠。这些年龄比先前为 ASSA 确定的年龄要年轻，岛弧链将影响中中新世期间南斯科舍海的深海通道。地球化学分析表明，岩浆活动来自一个枯竭的软流圈源，经过俯冲改造，类似于今天的南桑威奇岛弧。来自 Discovery Bank 的证据表明，弧火山作用在预先存在的玄武质地壳上发展，可能与威德尔海俯冲有关，尽管淹没的海岸以中新世弧火山岩为主。弧后海山线性链的识别和成像也提供了海洋内岛弧环境的证据，这是当今南三明治岛弧中几个火山中心的特征。来自邻近布鲁斯班克地形高地的基性火山岩，包括超基性岩性，也已被调查，并被证明是在与探索班火山岩不同的构造环境中生成的。它们被解释为与晚始新世期间扫描盆地的开放有关，或者与辉长岩太平洋边缘异常的潜在远端证据有关。来自邻近布鲁斯班克地形高地的火山岩也已被调查，并被证明是在与探索班克火山岩不同的构造环境中生成的。它们被解释为与晚始新世期间扫描盆地的开放有关，或者与辉长岩太平洋边缘异常的潜在远端证据有关。来自邻近布鲁斯班克地形高地的火山岩也已被调查，并被证明是在与探索班克火山岩不同的构造环境中生成的。它们被解释为与晚始新世期间扫描盆地的开放有关，或者与辉长岩太平洋边缘异常的潜在远端证据有关。