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该地区中新世——渐新世火山作用是广泛分布于澳大利亚东部范围更大的第三纪火山省的一部份。在昆士兰东南部,火山作用明显地表现出双峰特点,它们喷发自6个主要的以及许多较小的火山中心。在体积上镁铁质熔岩占优势,在成份上,从霞石—标准矿物分子连续地过渡到石英—标准矿物分子(以下简称ne型熔岩,Q型熔岩),以中长石—标准矿物分子熔岩占优势;Mg/Mg+∑Fe(原子比)的变化范围为30—60;K_2O为0.42—2.93%,而TiO_2是0.81—3.6%。斑晶含量低(以体积计,平均为6.7%),有橄榄石(Fa_(18-75);在富镁斑晶中局部含有Cr-尖晶石包体)、斜长石(An25—68),普通辉石一般少见。在斯普林休尔(Springsure)火山中心熔岩中见到的普通辉石相对高铝。在某些Q型熔岩中产出很少的铝古铜辉石。基质矿物由普通辉石、橄榄石(Fa33—77)、长石(从拉长石到歪长石及透长石)、Fe-Ti氧化物及磷灰石组成。在许多Q-型熔岩中,虽普遍产出亚钙质及易变辉石质的辉石,但斜方辉石仍相对少见。在矿物学上,很难区分ne型和Ol型熔岩以及某些Q型熔岩,从化学分类观点看,这些熔岩都可归入夏威夷岩(hawaiite)这一术语中。在本文中,拉斑玄武质安山岩这一术语是指含有贫钙辉石基质相的Q型熔岩。
The Miocene-Oligocene volcanism in the area is part of a larger Tertiary Volcano that is widely distributed in the eastern part of Australia. In southeastern Queensland, volcanism clearly showed bimodal characteristics, erupting from six major and many smaller volcanic centers. In terms of volume, the mafic lava predominates, and on the composition, from nepheline-standard mineral molecules to the quartz-standard mineral molecules (hereinafter referred to as ne-type lava, Q-type lava) Lava dominant; Mg / Mg + ΣFe (atomic ratio) of the range of 30-60; K_2O 0.42-2.93%, while the TiO_2 is 0.81-3.6%. The content of plagins was low (average 6.7% by volume), with olivine (Fa_ (18-75); locally Cr-rich spinel inclusions in Mg-rich platyclasts), plagioclase (An25-68 ), Ordinary pyroxenes are rare. The pyroxenes found in the lava in the volcanic center of Springsure are relatively high in aluminum. In some Q lavas, few aluminum-copper pyroxenes are produced. The matrix minerals are composed of pyroxene, olivine (Fa33-77), feldspar (from labradorite to plagioclase and peridotite), Fe-Ti oxide and apatite. In many Q-type lavas, orthopyroxene remains relatively rare, although calcite and peridotite are widely produced. Mineralogically, it is difficult to distinguish between Ne and Ol lavas and some Q lavas, which, from the chemical classification point of view, can be classed as the term hawaiite. In this paper, the term tholeiite andesite refers to Q-type lava that contains a poorly doped pyroxene matrix phase.