This allocutio refers to two formularies for a Mass with the title of “Mary, Image and Mother of the Church”. Though they are not assigned to the Lenten season in the Collection of Masses of the Blessed Virgin Mary, they do nevertheless have a relation to the themes of the Lenten season.
The title of these Masses has two origins that are distinct, but in fact also related. The first is from the chapter of Vatican II’s Constitution on the Sacred Liturgy which sets out principles for the celebration of the Liturgical year (my emphasis added):
In celebrating this annual cycle of Christ's mysteries, holy Church honors with especial love the Blessed Mary, Mother of God, who is joined by an inseparable bond to the saving work of her Son. In her the Church holds up and admires the most excellent fruit of the redemption, and joyfully contemplates, as in a faultless image, that which she herself desires and hopes wholly to be.The second origin is Pope Paul VI’s solemn proclamation of the title of Mary as “Mother of the Church” at the end of the third session of the Vatican council. Reflecting on the Council’s Constitution on the Church, with its chapter dedicated to the Virgin Mary, Paul VI considered this a most opportune moment to declare in explicit terms the maternal role of Mary with regard to the Church, and to do so using officially the title of Mary as Mother of the Church:
To the glory of the Blessed Virgin and for our consolation we declare Mary most Holy to be Mother of the Church, that is of all the Christian people, be they the faithful or the Pastors, who call her Mother most loved; and we establish that with this title all the Christian people will from now on offer even more honour to the Mother of God and put before her their supplications.If we look at some of the texts for the third formulary of the Mass of the Blessed Virgin Mary, Mother of the Church, we can see these origins and we can see the aspects pertinent to the Lenten season (my emphases added):
Lord our God, through your power and goodness the Blessed Virgin, the fairest fruit of your redeeming love, shines forth as the perfect image of the Church; grant to your people on their pilgrim way on earth that, with eyes fixed on Mary, they may follow closely in the footsteps of her Son until they come to that fullness of glory, which now they contemplate in his mother, with hearts filled with joy.The prayer that we might follow in the footsteps of Christ reflects the penitential aspect of Lent. It reflects a theme of Mary as Disciple of the Lord that we have already seen, and which here is implied as a model for the discipleship of believers.
Lord, grant that this offering, consecrated to your glory, may purify your people and fashion your Church more and more in that image of Christ, which it admires and praises in his glorious mother.This prayer reflects both the baptismal and penitential aspects of Lent in its reference to purification and taking on the image of Christ, thought the baptismal aspect is most prominent.
You have given the Blessed Virgin Mary to your Church as the perfect image of its role as mother and of its future glory. She is a virgin unsurpassed in purity of faith, a bride joined to Christ in an unbreakable bond of love and united with him in his suffering. She is a mother by the overshadowing of the Holy Spirit, filled with loving concern for all her children.Again we can see both a penitential and a baptismal character, the baptismal character being particularly expressed by her title as mother, here referring to her title as Mother of the Church where the previous prayers refer to Mary’s motherhood as motherhood of Christ.
If we look at the texts of the first formulary of a Mass of the Blessed Virgin Mary, Image and Mother of the Church, we find similar baptismal and penitential themes. There is, though, an emphasis on the preaching of the Gospel and the drawing of people to the Christ and the Church, in which one might see the catechumenal sense of Lent as preparation for baptism.
God of mercies, your only Son, while hanging on the cross, appointed the Blessed Virgin Mary, his mother, to be our mother also. Like her and under her loving care, may your Church grow day by day, rejoice in the holiness of its children and so attract to itself all the peoples of the earth.
She accepted God’s parting gift of love as she stood beneath the cross and so became the mother of all those who were brought to life through the death of her only Son.
Lord god, we have received the foretaste and promise of the fullness of redemption. We pray that your Church, through the intercession of the Virgin Mother, may proclaim the Gospel to all nations and by the power of the Spirit reach to the ends of the earth.
 Vatican II Sacrosanctum Concilium n.103.
 Paul VI Allocutio at the Solemn Closing of the Third Session of the Second Vatican Council nn.29-30.
 Mass of the Blessed Virgin Mary, Image and Mother of the Church III, Opening Prayer.
 Mass of the Blessed Virgin Mary, Image and Mother of the Church III, Prayer over the Gifts.
 Mass of the Blessed Virgin Mary, Image and Mother of the Church III, Preface.
 Mass of the Blessed Virgin Mary, Image and Mother of the Church I, Opening Prayer
 Mass of the Blessed Virgin Mary, Image and Mother of the Church I, Preface
 Mass of the Blessed Virgin Mary, Image and Mother of the Church I, Prayer after Communion.