Geology, Mineralogy and Geochemistry of the Late Cenozoic McMurdo Volcanic Group, Victoria Land, Antarctica
Geology, Mineralogy and Geochemistry of the Late Cenozoic McMurdo Volcanic Group, Victoria Land, Antarctica
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南极洲维多利亚地晚新生代麦克默多火山群的地质学、矿物学和地球化学
DOI：
10.26686/wgtn.16945573
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发表时间：
1976
影响因子：
4
通讯作者：
P. Kyle
中科院分区：
文献类型：
--
作者：
P. Kyle
麦克默多火山群的岩石以成层火山、盾状火山、火山渣锥、火山塞、火山流和火山堆的形式出现，最高可达沿着南极洲山脉罗斯海边缘的4000米，构成了南极洲大陆边缘以北300公里处的巴莱尼群岛。岩石主要是不饱和的，范围从碱性玄武岩和碧玄岩粗面岩和响岩。四个火山省被确认; Balleny，Hallett，墨尔本和埃里伯斯。巴莱尼火山区位于南太平洋转换断层的沿着。岩石主要是碧玄岩。哈雷特火山区沿着维多利亚州北方海岸，由四个细长的火山堆组成，它们由大量的玻璃碎屑岩、凝灰岩、角砾岩组成，并被陆上喷发产物覆盖。熔岩是碧玄岩/碱性玄武岩-粗面岩-石英粗面岩组合，在过去的7百万年中被挤出。墨尔本火山省横跨北方维多利亚地的跨南极山脉，年龄从0到7百万年不等一个中间和粗面质熔岩的中央岩套形成了成层火山、火山锥和火山塞，而许多小的碧玄岩露头构成了一个局部岩套。三个熔岩谱系，从分化产生的，是公认的。1)昂宿星团和霸王山的熔岩由温和含钾的粗安岩-三甲石-钾粗面岩-过碱性钾粗面岩谱系组成。主要，微量和稀土元素（REE）数据表明，演化的橄榄石，单斜辉石，磁铁矿，磷灰石和长石的分离结晶。2)在昂宿星团发现的碧玄岩-霞石夏威夷岩-霞石mugarite-霞石benmoreite谱系被认为是橄榄石、单斜辉石、钾霞石、磁铁矿、磷灰石和长石的分离结晶的结果。3)仅在墨尔本山出现过饱和（Q = 0 ~ 18%）的强钾质石英粗安岩-石英粗面岩谱系。埃里伯斯火山区覆盖了维多利亚地南部所有的麦克默多火山群岩石。埃里伯斯山本身仍然活跃，但该省包括1500万年前的岩石。两个熔岩谱系非常相似的化学被确认：1）Erebus谱系由强烈的斑状霞石夏威夷-霞石benmocalonite-斜长岩响岩。长石、单斜辉石、橄榄石、磁铁矿和磷灰石的斑晶是其特征。该谱系的化学性质与斑晶相的分步结晶相容。2)钾霞石谱系由碧玄岩-霞石夏威夷岩-霞石莫杰拉岩-霞石钠闪石-钾霞石响岩-辉石响岩组成。单斜辉石（Wo 44 -48 En 40 -48 Fs 7 -14）普遍存在，钾霞石常见于所有中间熔岩中，原生橄榄石（Fa 12至Fa 26）仅限于碧玄岩中。从小屋点半岛熔岩的主要元素质量平衡模型建议形成的橄榄石，单斜辉石，尖晶石（包括磁铁矿和钛铁矿），钾霞石，长石和磷灰石的分离结晶。中稀土元素明显亏损，与钾镁矾分馏作用一致。稀土元素丰度进行了评估，使用的质量平衡模型和公布的分配系数。计算的稀土元素丰度与实测值吻合良好。“不相容”元素Pb、Rb、Cs、Th和U的丰度与模型不一致，并援引“挥发物富集”过程来解释其丰度。在埃里伯斯火山区，钾霞石系的中间熔岩非常罕见，仅出现在赫特角半岛和布朗半岛。其他地区以碧玄岩和响岩熔岩为主。然而，这些被认为是通过类似于小屋点半岛熔岩的分离结晶过程形成的。Erebus谱系熔岩分化在较高的温度和较低的PH 2 O比那些kaersutite谱系，其特征的罗斯岛的外围。稀土元素丰度和实验熔融研究的比较表明，DVDP碧玄岩起源于低程度的部分熔融（1-5%）的含水石榴橄榄岩地幔在25-30千巴的压力。这些数据表明，罗斯岛是地幔柱的所在地，直径约100公里，中心位于埃里伯斯山。
Rocks of the McMurdo Volcanic Group occur as stratovolcanoes, shield volcanoes, scoria cones, plugs, flows and volcanic piles up to 4000 m high along the Ross Sea margin of the Transantarctic Mountains and make up the Balleny Islands 300 km north of the Antarctic continental margin. The rocks are predominantly undersaturated and range from alkali basalt and basanite to trachyte and phonolite. Four volcanic provinces are recognised; Balleny, Hallett, Melbourne and Erebus. The Balleny volcanic province is situated along a transform fault in the South Pacific Ocean. The rocks are predominantly basanite. Hallett volcanic province occurs along the coast of northern Victoria Land as four elongate piles formed extensive of hyaloclastites, tuffs, breccias and capped by subaerial eruptive products. The lavas are a basanite/alkali basalt-trachyte-quartz trachyte association, and were extruded over the last 7 m.y. Melbourne volcanic province stretches across the Transantarctic Mountains in northern Victoria Land and ranges in age from 0 to 7 m.y. A Central Suite of intermediate and trachytic lavas form stratovolcanoes, cones and plugs, while many small basanite outcrops constitute a Local Suite. Three lava lineages, resulting from differentiation, are recognised. 1) Lavas at The Pleiades and Mt Overlord consist of a mildly potassic trachyandesite-tristanite-K-trachyte-peralkaline K-trachyte lineage. Major, trace and rare earth element (REE) data suggest evolution by fractional crystallization of olivine, clinopyroxene, magnetite, apatite and feldspar. 2) A basanite-nepheline hawaiite-nepheline mugearite-nepheline benmoreite lineage, found at The Pleiades is believed to result from fractional crystallization of olivine, clinopyroxene, kaersutite, magnetite, apatite and feldspar. 3) An oversaturated (Q = 0 to 18%) strongly potassic quartz trachyandesite-quartz tristanite-quartz trachyte lineage occurs at only Mt Melbourne. The Erebus volcanic province covers all McMurdo Volcanic Group rocks in south Victoria Land. Mt Erebus itself is still active, but the province includes rocks as old as 15 m.y. Two lava lineages very similar chemically are recognised: 1) The Erebus lineage consists of strongly porphyritic nepheline hawaiite-nepheline benmoreite-anorthoclase phonolite. Phenocrysts of feldspar, clinopyroxene, olivine, magnetite and apatite are characteristic. The chemistry of the lineage is compatible with fractional crystallization of the phenocryst phases. 2) A kaersutite lineage consists of basanite-nepheline hawaiite-nepheline mugearite-nepheline benmoreite-kaersutite phonolite-pyroxene phonolite. Clinopyroxene (Wo44-48 En40-48 Fs7-14) is ubiquitous, kaersutite is common in all intermediate lavas and primary olivine (Fa12 to Fa26) is confined to the basanites. Major element mass balance models for lavas from Hut Point Peninsula suggest formation by fractional crystallization of olivine, clinopyroxene, spinel (includes magnetite and ilmenite), kaersutite, feldspar and apatite. Middle REE show a marked depletion consistent with kaersutite fractionation. REE abundances were evaluated using the mass balance models and published partition coefficients. Calculated REE abundances show excellent agreement with the measured values. Abundances of "incompatible" elements Pb, Rb, Cs, Th and U are not consistent with the models and "volatile enrichment" processes are invoked to explain their abundances. Intermediate lavas of the kaersutite lineage are rare in the Erebus volcanic province, occurring only at Hut Point Peninsula and Brown Peninsula. At other areas basanite and phonolite lavas predominate. However these are considered to form by fractional crystallization processes similar to Hut Point Peninsula lavas. Erebus lineage lavas differentiated at higher temperatures and, lower PH2O than those of the kaersutite lineage, which characterize the periphery of Ross Island. REE abundances and comparison with experimental melting studies indicate DVDP basanite originated by a low degree of partial melting (1-5%) of a hydrous garnet peridotite mantle at pressures of 25-30 kbars. These data suggest that Ross Island is the site of a mantle plume with a diameter of, about 100 km and centred on Mt Erebus.