In the western Himalaya there are metabasic volcanics said to be intercalated with metasediments of supposedly proterozoic age. The metasediments are intruded lower Paleozoic granite. The granite has subhedral to euhedral plagioclase laths (igneous signature). In other parts it has dominant muscovite and or both muscovite and biotite. Within the granite there is a gabbro body which is largely undeformed.
What dating methods should be used for each of these to understand their relative timing?
Firstly, it is essential to identify the accessory phases present in the gabbro. A conventional method for dating mafic rocks is U-Pb in baddeleyite, provided it is available in your rock. If the gabbro intrusion is related to felsic (or granitic) magmatism, zircon will likely occur in the gabbro. There are also alternative methods which use oxides (such as magnetite) or sulfides (e.g. pyrite), but they might be more demanding and less accurate in determining the crystallization age. In some cases, you may end up with the age of a later event instead.
I agree that zircon and baddeleyite are the most reliable phases to be used in such a case. Also, if your gabbro contains any magmatic amphibole, you may apply 40Ar/39 method for amphibole separates (however you will obtain the age of the isotopic system closure at ca. 500C, not the age of magma crystallization). The constraints on the age of the host clastic rocks may be obtained by U-Pb dating of detrital zircons.