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通常认为大洋岩石圈俯冲到地球深部，从而导致地幔的对流并产生地幔的不均一性。然而，大洋岩石圈作为一个整体可能并非均匀地俯冲：即由于化学成分、密度和熔融温度的差异，玄武岩壳与其下伏橄榄岩层俯冲到地球深部后的情况可能有所不同。有人认为俯冲的玄武岩壳可能在地幔中６６０ ｋｍ 处的不连续面附近形成一个浮体，且该浮体至少延伸至８００ ｋｍ 的深处，从而产生可能由于重力捕获作用形成的石榴石岩层。本文报道大洋中脊玄武岩在高达６４ ＧＰａ 压力下（相当于１ ５００ ｋｍ 的深度）的相态关系和熔融温度。我们的研究发现当俯冲的玄武岩壳在大约７２０ ｋｍ 的深处转化为钙钛岩的岩性特征时不再是浮体，并且在该转换带压力与温度呈正相关，这与橄榄岩正好相反。据此可推测，具钙钛岩岩性特征的玄武岩壳有可能因重力作用而下沉至深部地幔。熔融实验资料表明，在下地幔底部，当温度超过４ ０００ Ｋ时，玄武岩壳将会产生熔融。
The oceanic lithosphere is generally thought to subduct deep into the earth, causing convection of the mantle and creating mantle heterogeneity. However, the oceanic lithosphere as a whole may not be uniformly subducted: the basaltic shell and its underlying peridotites may subduct deep into the Earth due to differences in chemical composition, density and melting temperature. It is believed that the subducted basalt crust may form a buoy near the discontinuity at 660 km in the mantle and the buoy may extend at least to a depth of 800 km resulting in garnet formations that may have formed as a result of gravity catching. This paper reports the phase relationship and melting temperature of mid-oceanic basalts at pressures as high as 64 GPa (equivalent to a depth of 1 500 km). Our study found that the subducted basalt crust no longer floats when converted to lithological features of peridotite at a depth of about 720 km and that the pressure in the transition zone is positively correlated with temperature, as opposed to peridotite. It can be speculated that basalt shells with lithological characteristics of calcium-titanium rocks may sink to the deep mantle due to gravity. Melting experimental data show that at the bottom of the lower mantle, the basalt shell will melt when the temperature exceeds 4 000 K.