Lost primordial continents
Lost primordial continents
复制标题
DOI：
10.1016/j.gr.2009.05.012
复制
发表时间：
2009-12
影响因子：
6.1
通讯作者：
K. Kawai;T. Tsuchiya;J. Tsuchiya;S. Maruyama
中科院分区：
文献类型：
--
作者：
K. Kawai;T. Tsuchiya;J. Tsuchiya;S. Maruyama
根据组成矿物相的压力-体积-温度状态方程，研究了下地幔中一些代表性成分的体积密度变化。在300 K温度和下地幔压力条件下，研究了软锰矿、黑锰矿、海中脊玄武岩（MORB）、闪长岩（TTG）、花岗闪长岩（TTG）和斜长岩的密度变化。整个下地幔中MORB的密度大于软锰矿的密度，而黑锰矿的密度略低于软锰矿的密度。下地幔中斜长岩的密度一般与软锰矿相当，且最下层地幔密度较大，而整个下地幔中TTG的密度均低于软锰矿。上述结果对原始大陆、TTG和斜长岩地壳的命运具有重要意义。虽然俯冲的TTG可能停滞在地幔过渡带，但密集的俯冲斜长地壳可能下沉到核幔边界（CMB），因此可能是紧邻CMB上方的D”层的主要组成部分。因此，我们提出，除了地球表面的大陆之外，在过渡带和紧接在CMB上方的地幔中可能存在大量的大陆物质。
We investigate the bulk density variations of some representative compositions for the lower mantle based on the pressure–volume–temperature equation of state of the constituent mineral phases. The density variations of pyrolite, harzburgite, mid-ocean ridge basalt (MORB), tonalite–trondhjemite–granodiorite (TTG), and anorthosite are studied at a temperature of 300 K and at lower mantle pressures. The density of MORB is greater than that of pyrolite throughout the lower mantle, while the density of harzburgite is slightly lower than that of pyrolite. The density of anorthosite is comparable to that of pyrolite in the lower mantle in general, and greater in the lowermost mantle, while the density of TTG is lower than pyrolite throughout the lower mantle. The above results have important implications for the fate of primordial continents, TTG and anorthosite crust. While subducted TTG might be stagnant in the mantle transition zone, dense subducted anorthositic crust could be expected to sink to the core–mantle boundary (CMB) and thus might be a major component of the D" layer immediately above the CMB. Thus, we propose that significant bodies of continental material could be present in the mantle in the transition zone and immediately above the CMB, in addition to the continents on the Earth's surface.