We present the first in a series of papers studying with Chandra the X-ray properties of a sample of 28 early-type galaxies which span \sim 3 orders of magnitude in X-ray luminosity ( { L _ { X } } ) .
We report emission-weighted Fe abundance ( { Z _ { Fe } } ) constraints and , for many of the galaxies , abundance constraints for key elements such as O , Ne , Mg , Si , S and Ni .
We find no evidence of the very sub-solar { Z _ { Fe } } historically reported , confirming a trend in recent X-ray observations of bright galaxies and groups , nor do we find any correlation between { Z _ { Fe } } and luminosity .
Except in one case we do not find evidence for a multi-phase interstellar medium ( ISM ) , indicating that multi-temperature fits required in previous ASCA analysis arose due to the strong temperature gradients which we are able to resolve with Chandra .
We compare the stellar { Z _ { Fe } } , estimated from simple stellar population model fits , to that of the hot gas .
Excepting one possible outlier we find no evidence that the gas is substantially more metal-poor than the stars and , in a few systems , { Z _ { Fe } } is higher in the ISM .
In general , however , the two components exhibit similar metallicities , which is inconsistent with both galactic wind models and recent hierarchical chemical enrichment simulations .
Adopting standard SNIa and SNII metal yields our abundance ratio constraints imply 66 \pm 11 % of the Fe within the ISM was produced in SNIa , which is remarkably similar to the Solar neighbourhood , and implies similar enrichment histories for the cold ISM in a spiral and the hot ISM in elliptical galaxies .
Although these values are sensitive to the considerable systematic uncertainty in the supernova yields , they are also in very good agreement with observations of more massive systems .
These results indicate a remarkable degree of homology in the enrichment process operating from cluster scales to low-to-intermediate { L _ { X } } galaxies .
In addition the data uniformly exhibit the low { Z _ { O } } / { Z _ { Mg } } abundance ratios which have been reported in the centres of clusters , groups and some galaxies .
This is inconsistent with the standard calculations of metal production in SNII and may indicate an additional source of \alpha -element enrichment , such as Population III hypernovae .