Abstract:
Olivine is a ubiquitous mineral inmafic-ultramafic rocks and has been widely used as a mineral marker in various
geological processes. However, its development of trace elements is limited. Here we present newly-obtained
trace element data 7Li, 27Al, 29Si, 31P, 43Ca, 45Sc, 49Ti, 51V, 53Cr, 55Mn, 59Co, 60Ni, and 66Zn of olivine in typicalmantle
xenoliths, mantle peridotites in ophiolites, and plutonic rocks from layered and Alaskan-type intrusions to develop
trace element proxies for the petrogenesis, mineralization and discrimination of various mafic-ultramafic
rocks. Residual olivine grains in mantle xenoliths and ophiolitic peridotites, which represent residues of mantle
melting, have higher Ni/Co (>20) and Ni/Mn (>2) ratios than magmatic olivine (Ni/Co < 20, Ni/Mn < 2), which
are consistent with the compatibilities of these elements during partial melting and magma differentiation.
Lower Ni content, and lower Ni/Co and Ni/Mn ratios at a given Fo content can distinguish olivine in Alaskantype
intrusions from layered intrusions, reflecting the nature of their mantle sources. The V and Sc contents
and V/Sc ratios in olivine can distinguish mantle xenoliths (V > 2 ppm, V/Sc > 0.5) from ophiolitic peridotites
(V<2 ppm, V/Sc< 0.5), indicating a more reduced state of continental lithospheric mantle compared to the oceanic
lithospheric mantle. As a consequence, the four occurrences of mafic-ultramafic rocks can be distinguished
by olivine with (Sc × 10)-(Ti × 2)-Zn and V/Sc-(Co/Ni × 2)-(Zn/Mn× 5) ternary diagrams. In addition, Li, Ti and P
contents in olivine are good tracers of melt/fluid metasomatism, whereas Ni/Co, Ni/Mn and Mn/Zn ratios are
indicators of chromite mineralization. Therefore, trace elements in olivine can be used as chemical proxies to distinguish
the origin of various mafic-ultramafic rocks, as well as the processes by which they evolved.
