A few years ago a coworker got married in a Catholic church by a deacon. The eucharist was not performed in the accompanying service. Why was the deacon allowed to perform one sacrament (marriage) and not another (the eucharist)? What actions and practices can a priest and only a priest perform?
My connections to Catholicism are entirely second-hand (Cat’lic high school, family-in-law nominally Catholic including an uncle who spent 50 years in Haiti, etc.) but was this perhaps a case where it was not a fully church-sanctioned marriage? Could it have been a non-sacramental marriage of people who did not qualify or want a church marriage but had the favor of using the church and a lesser official to perform the ceremony?
In most states, almost anyone can perform a marriage ceremony; in California, the legal stance is that you marry yourselves but need a presiding official. I could see a relaxed parish allowing such “outside” weddings as long as the priest did not perform them.
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Roman Catholic? The deacon did not perform the marriage sacrament; the bride and groom did. He was the Witness for the Church and probably for the marriage license.
Ha-ha! You’ll have to try harder than that, ninja sailor!
It was performed in a Catholic church, and I believe the groom was not Catholic. What surprised me was they conducted the entire mass minus the Eucharist, which doesn’t make a lot of sense if they just wanted someone to officiate.
First of all, priests cannot licitly perform the sacrament of matrimony at all, and what you saw a few years ago was probably not a deacon performing it, either. The sacrament of matrimony is performed by the couple being married: The priest or deacon is merely officiating over the ceremony, not performing.
Going through the list of sacraments:
Anyone at all (even a non-Christian) can baptize, though it ought properly to be done by a priest, if possible.
Only a priest can consecrate the Eucharist, but a layperson in good standing with the Church and who has gone through a small amount of training can administer it, and often do (a typical mass will have the priest and perhaps 3-10 lay eucharistic ministers serving).
Confirmation can be done by a priest, but outside of certain circumstances it ought to be done by a bishop.
The sacraments of penance and of annointing of the sick can be administered by any baptized person, but only in dire necessity: As with baptism, it ought to be done by a priest.
Matrimony can be performed by anyone, since it’s performed by the couple getting married. A marriage within the church should be officiated over by a priest or deacon.
Holy Orders can only be performed by a bishop.
It’s worth noting that, sacramentally speaking, there is no distinction between bishops. There is no sacrament that the Pope receives or performs that cannot be done by all bishops.
Only a priest may administer the sacrament of Anointing of the Sick (formerly known as Extreme Unction).
Edited to add: I note this statement, which reflects what I was taught in school, is contradicted by Chronos, above. I defer to his greater knowledge.
Performing the Eucharist is the mass. They may have had the whole service except for the Mass, but you can’t have any part of the Mass proper without the Eucharist.
When speaking about “who is allowed to do what” in Roman Catholicism, there are two very important and very different concepts to start out with, validity and licitness. The rules on who is capable of performing a sacrament in a most fundamental sense relate to validity. Whether or not a person is allowed to perform the sacrament as a matter of institutional discipline and procedures relates to licitness. For example, a priest is ontologically capable of giving Confirmation to a person (and the person would not have to get it again), but if they do so without their bishop’s permission, they are In Trouble ™ and may need to go to confession and/or may be disciplined by a pay cut, suspension, or by being defrocked. In theory, anyone can perform baptism, according to the Catholic Church, but if a non-priest baptizes without permission in a non-emergency situation, that is “illicit”, but “valid”.
Here are some sources to start out:
http://www.americancatholic.org/features/special/default.aspx?id=29
So, it sounds like three things did and did not happen at that time:
Liturgy of the Eucharist - blessings, wine, water, waving of hands over crackers, eating crackers, drinking wine
Liturgy of the Word - the rest of the praying and Catholic calisthenics
Sacrament of Marriage
The three are often interwoven so they appear to be one thing with several parts, but on a technical level, they are not the same event. The Deacon did one, the bride and groom did another, and with no priest there, the Liturgy of the Eucharist was left out…very possibly because the groom wasn’t Catholic. Non-Catholics can participate in the Liturgy of the Word, but they cannot participate in the Eucharist. Sounds like a very accommodating way for the Church to let them get married in her church, actually.
When we got married in the Catholic Church, we had the option of the full mass (including the Eucharist) or just the Liturgy of the Word and Marriage Rite.
Being Italian, we opted to do the entire thing, of course. 
Nah, don’t defer to me. Let’s wait until Bricker or Tomndeb shows up, and then we can both defer to them.
And even though it requires permission from the bishop, there is one situation where it’s common for a priest to perform Confirmation: When an adult is joining the church (through the process called RCIA, or Rite of Christian Initiation for Adults), the last step is traditionally taken at the Easter Vigil mass, when the candidates are baptized, confirmed, and receive their First Communion (or some subset of that, if they already have some of those sacraments). Since this is done in all churches (or at least, all that have candidates), and since the bishop can only be in one place at a time on that night, in this situation confirmation is typically performed by priests.
Same thing here, except he’s the Italian Catholic and I’m neither (and did not convert). We went for the Eucharist too while we were at it.
Same but being aussie we thought “nah cut it short so we can get on the piss quicker”
In the Church of England, the one thing that can only be done by an ordained priest is the blessing of the sacrament.
In our church we have a pastor who is not fully ordained. He is licensed to marry couples and can officiate at communion but the bread and wine has to be blessed in advance by a priest. Although it is popularly believed that a couple are married when the priest says “I now pronounce you man and wife”, they are not legally married until the register is signed and witnessed.
Deacons in our church are ordained priests with a wider role in the diocese. Only a Bishop can carry out a confirmation.
Deacons are ordained in the Catholic church, too. There are three levels of ordination: Deacons, priests, and bishops.
Technically, you’re supposed to say my name three times while looking in a mirror.
Only a priest may administer the sacrament of penance. Moreover, for the absolution granted by the penance to be effective, the priest must have the faculty to hear the confession of that penitent. The Pope and cardinals of the Church may hear any confession anywhere. A bishop may hear confession anywhere in his own diocese and anywhere else, unless the local bishop has forbidden it. A metropolitan archbishop may hear confessions in his suffragan dioceses.
A pastor may hear his parishioners confession, and the local bishop may (and typically always does) allow all his priests to hear confessions in his diocese.
Other rules apply to the Superior of a religious order and to those who are equivalent in law to a diocesan bishop. (Detail if anyone’s interested). A priest appointed as chaplain to an organization may always hear the confession of a member of that organization, geographical barriers not withstanding.
Only a priest may administer the Anointing of the Sick.
Sorry, Chronos…
Its only proper scientific to ask WHY IS IT SO ? … with the expectation of scientifically valid answer of course 
People keep conflating two separate, distinct marriages which actually take place under two separate, distinct, sets of law.
The canonical marriage, as has been explained by most posters, is actually performed by the spouses (this isn’t limited to the RCC at all, by the way). The officiant, if any, is merely a witness who performs some paperwork; this paperwork officializes the creation of the marriage bond but it’s just a shortcut for asking everybody in town whether those two are married or not. If the compromise and dedication do not exist beforehand, the paper will not magic it into place. A canonical marriage is one that’s recognized as valid by canon law; that is, by the Church. Recognition by canon law does not require a wedding, or the presence of an ordained officiant at it if it did take place.
The civil marriage may or may not be concurrent with a canonical marriage; there are locations where both can have the same officiant; others where they must have the same officiant; others where they cannot have the same officiant. A civil marriage is one recognized by a government. In locations where common-law marriage is recognized, officiants and paperwork are not required; in locations where common-law marriage is not recognized, officiants and paperwork are required.
Even when they have been officialized at the same time, the two marriages are not a single bond. Divorce does not annul; annulment does not divorce.